-3 T^^'-'^? ^^'^ ddrB\unoKi room library \- UNITED STATES DEPARTMENT OF AGRICULTURE MISCELLANEOUS PUBLICATION No. 74 WASHINGTON, D. C. MAY 1930 AN ANNOTATED LIST OF THE IMPORTANT NORTH AMERICAN FOREST INSECTS Compiled by F. C. Craighead, Principal Entoviologisl in Charge and William Middleton, Associate Ento7nologist Division of Forest Insects, Bureau of Entomology Page Oovernment projectsrelating (o forest iriFerts. 1 Tree-killing bark beetles 1 Insects injurious to forest products 2 Insects affecting forest management 3 Insects injurious to shade trees and ornamental shrubs.. 3 The most Important forest insects 4 Tree-killing bark beetles 4 Insects boring in living trees 6 CONTENTS Page The most important forest insects— Con td. Insects affecting forest products U •Insects affecting seeds, forest reproduc- tion, and nursery plants 15 Defoliating insects 13 Literature cited 23 Appendix...... 27 Index . 28 GOVERNMENT PROJECTS RELATING TO FOREST INSECTS The investigations by the United States Government of the insects affecting forest trees, forest products, and shade trees are centered in the division of forest insects of the Bureau of Entomology. The investigations carried on by the division are grouped for administra- tive convenience into projects, the most important of which are briefly described in the following paragraphs. TREE-KILLING BARK BEETLES Several species of tree-killing bark beetles of the genus Dendroc- tonus destroy annuallv over 6.000,000.000 feet of timber valued at from $15,000,000 to $20,000,000. Biological investigations of these beetles and the associated cooperation with Federal and private agencies in their control constitute one of the major activities of the division. The biological studies relate not only to the seasonal history and habits of the species, but also to the environmental fac- tors governing the behavior of the insects in all stages of develop- ment, such as the part played b}' predators, parasites, and other associated insects; the effects of climate, forest type, and site: the characteristics of the trees selected for attack: and (he reaction of the tree itself during and after attack. All these factors, to which 97801'— 30 1 1 2 MISC. PUBLICATION 7 4, U. S. DEPT. OF AGRICULTURE murh attention is given, have an important bearing on brood de- velopment, and their study is throwing considerable light on the causes underlying the rise and fall of bark-beetle epidemics. Re- sults have already been obtained which will have an application in timber-sale regulations, logging opei'ations, and slash disposal. In certain cases, it has been possible, as a result of these researches, to predict the decline of epidemics and thus to save considerable money that might otherwise have been expended needlessly in direct control. These studies are centered on the national forests in California, Oregon, Montana. Arizona, Colorado, and North Carolina. As the stumpage value of timber increases in the Western States, the protection of the great stands of mature timber from the.se baik- beetle losses constitutes an ever-growing problem. A considerable part of the funds appropriated is utilized in rendering service to agencies cooperating in ])rotection from this class of insects. This service consists largely in the direction and administration of the technical features of control projects against tree-killing bark beetles as well as in the analysis of the results. In this Avork close coopera- tion is maintained with the Forest Service, the National Park Serv- ice, the Office of Indian Affairs, and private owners. At the request of these organizations or individuals surveys are made of l)eetle- infested areas antl recommendations given as to the advisability of control measures and as to the methods to be employed. Occasion- ally these i^rojects cover enormous areas and involve ver^' complex administrative details. Field laboratories for the regional administration of these inves- tigations are maintained at Coeur d'Alene. Idaho, and at Palo Alto. Calif. From four to six additional temporary bases are in use during the field season. INSECTS INJURIOUS TO FOREST PRODUCTS From a monetary standpoint, because of the higher values in- volved, insects destructive to forest products take an even greater annual toll than do the bark beetles. There are a great number of insects destructive to all forms of wood products from the green felled tree to the finished seasoned article. Much time and labor have been devoted to the development of methods for preventing damage to material of this character. In man}- cases all that is nec- essary for adequate protection is to make simple alterations in the methods of handling the material in the woods, or at the mill or warehouse. Suggested modifications of building codes to insure in- sect-proof construction are being widely adopted (87). Again, repellent sprays or dips are effectively employed, or the w^ood is im- pregnated with chemicals that ward off insect attack. Two experi- mental grounds are maintained — one at East Falls Church. Ya.. and the other in the Canal Zone, Panama — Avhere chemicals and wood preservatives are tested for efficiency against w^ood -boring insects. The Forest Products Laboratory of the Forest Service, at Madison, Wis., treats wood samples Avith preservatives to be tested at these experimental grounds. Cooperation is maintained, also, with many organizations interested in wood preservation. IMPORTANT NORTH AMERICAN FOREST INSECTS 6 INSECTS AFFECTING FOREST MANAGEMENT Cooperation with the Forest Service experiment stations forms another important line of activities. At present entomologists are stationed at, or are in close touch with, five of these experiment stations, namely, the Lake States Forest Experiment Station, St. Paul, Minn., the Northeastern Forest Experiment Station, Amherst, Mass., the Appalachian Forest Experiment Station, Asheville, N. C, the California Forest Experiment Station, Berkeley, Calif., and the North Pacific Forest Experiment Station at Portland, Oreg. It is planned for the future to have entomologists assigned to each station. The investigations carried on under this form of cooperation have to do wath the insect problems involved in the management of the more important forest types of the regions. Through studies of the major forest ijisect pests a better understanding of the "con- ditions favoring or retarding serious insect damage is gained, and this knowledge is made available to foresters so tliat it can be ap- plied in developing sound practices in timber culture. Some species of trees and some types of forests are little affected by insects, but in others insects may be the limiting factor in successful timber production. As better cultural practices for growing timber are attempted, the complex relations existing in the forests must be more fully understood to avoid fatal mistakes. Insects constitute one of the most important of the biotic factors. Although greatest recognition is given to their role as ilestroyers of green standing timber, other important activities that bring about changes in the composition of the forest can not be disregarded. Insects often increase the percentage of undesirable species of trees, inhibit the reproduction of certain desirable species, affect the rate of growth, and thus lengthen the rotation period and augment the ill effects of fire. Investigations dealing with these varied problems are under way. Some other problems of a more specific character are under in- vestigation, such as the entomological aspects of slash disposal (72), the interrelation of insects and forest fires {78, 79), turpentining practices and insect damage, insects affecting nursery practices, and insect injury to the seed of forest trees. INSECTS INJURIOUS TO SHADE TREES AND ORNAMENTAL SHRUBS Little in the way of investigation of insects affecting shade and ornamental trees and hardy shrubs is done at the present time, and most of the effort in this work is expended in service. There is a great and increasing demand from nnmicipal authorities, estate OAvners and managers, small pro])orty owners, tree surgeons, and nurserymen for advice on methods of handling their entomological problems. T)ie division of forest insects attempts to meet this demand by correspondence, publications, and occasional surveys and studies. Whenever possible, observations are made on important species and, where practical, experiments in methods of control and improvements in such methods are conducted. 4 MISC. PUBTJCATTON 7 4, TT. R. OKPt. OF AaRTCULTURE THE MOST IMPORTANT FOREST INSECTS This list includes those species of forest insects which are of the greatest economic importance at the present time. In the discussion of each species the common and technical names are given. There is added some information on the occurrence of the insect, the char- acter of damage or notable epidemics, and the most important or available references to it in literature. For the convenience of those not acquainted with the systematic classification of insects, the species listed have been arranged in grou])s according to the type of damage, such as burk beetles, leaf feeders, etc., and these groups are further subdivided as necessary. TREE-KILLING BARK BEETLES THE .SOUTHERN PINE BEETLE Dendroctonus frontalis Zinim. Tu the southeastern part of the United States the southern pine beetle stands out as the most important tree-killing bark beetle. This si)ecies becomes exceedingly abundant at irreguiai- intervals; and for several years, during one of these outbreaks, thousands of pines may be attacked and killed. In 1910 and 11)11 timber valued at over $•2,000,000 was destroyed (7, Jfi^ I^2)\ THE EASTERN SPRUCE BEETLE Dendroctonus piceaperda Hopk. In past years, before the virgin spruce forests of the Northeast were cut, this bark beetle was responsible for serious depredations. Of late years little timber has been killed by this beetle in the Unitetl States, though serious losses are reported from Canada {4^}. THE TURPENTINE BEETLES Dendroctonus valens Lee. Dendroctonus terebrans Oliv. The red turpentine beetle {Dendroctonus valens) and the black turpentine beetle (Z>. terebrans) are widely distributed in North America. They attack the bases and roots of practically all species of pine and spruce, causing the exudation of large masses of pit(;h. They rarely kill trees and are of importance more as a result of the attention they attract than because of the damage inflicted (i, 30, 4^, 46). THE MOUNTAIN PINE BEETLE Dendroctonus nionticolae Hopk. The mountain pine beetle has a very wide range, extending from the Sierras of central California through the northern Rockies into Canada. It attacks lodgepole, sugar, western white, and yellow pines. Nearly every year severe outbreaks are in progress in some part of this area. One notable infestation has been progressing since 1909 and now bids fair to destroy practically all the lodgepole pine on the Bitter Root and Beaverhead National Forests (^^, ^). » Reference is made by ilalif ii umbers iu ^jareii theses to Literature Cited, p. 23. IMPORTANT NORTH AMERICAN FOREST INSECTS 0 THE BLACK HILLS REETI.E Dendroctonus ponderosae Hopk. The Black Hills beetle is the most destructive enemy of yellow pine in the Rocky Mountain region,^ It has a marked tendency to increase suddenly to extraordinary numbers and, after destroying great quantities of timber, to subside quickly. Notable epidemics occurred in the Black Hills from 1898 to 1905 and in the Kaibab National Forest from 1920 to 1925 (^2). THE DOTTGLAS FIE BEETLE Dendroctonus pseudotsugae Hopk. The Douglas fir beetle is most destructive in the northern Eockiea and Canada. It seldom kills Douglas fir west of the Cascade Range. Outbreaks are local and sporadic, frequently associated with wind- throws, defoliations, or logging operations (^). THE WESTERN PINE BEBTTLE Dendroctonus brevioomis Lee. The western pine beetle occurs over practically the same territt^ry as the mountain pine beetle and extends to the southern limit of the yellow pine type in California. This species rarely causes spectacu- lar outbreaks but takes an annual toll of from 0.1 per cent to oc- casionally 5 per cent of the stand. It is of economic importance only in the western yellow pine forests (4^, 46). THE SOUTHWESTERN PINE BEETLE Dendroctonus barberi Hopk. In habits this species resembles its near kin, the w^j^rn pin<3 beetle, though it is not so destructive. Occasional outbreaks iu southern Colorado, Arizona, and New Mexico take a considerable toll of timber but are short-lived. The activities of the beetle in- crease in years of drought (4-^). THE JEFFBET PINE BEETLE Dendroctonus jeffreyi Hopk. The Jeffrey pine beetle restricts its activities entirely to the tree for which it is named. It is most injurious in the forests east of the Sierras, where it normally takes a small annual toll. Following a severe windstorm in the Inyo National Forest, Calif., some 6,000,000 feet of timber were killed by this species in 1924 and 1925 {42, 46). THE ENGBAVEB BEETTLES Ips spp. The engraver beetles of the genus Ips are vepresented by numerous species. They are usually associated with dying or recently felled softwoods. Occasionally they contribute to the death of timber weakened from other causes and may even kill outright healthy timber when they are present in great numbers. Sporadic out- 6 MTRC. PrBI.rCATION 74, U. S. DEPT. OF AGT^ICULTUKE breaks in which lar^^e groups of voiintr trees and occasionally mature trees are killed, often follow drought, windfalls, and slashmors. Epidemics will not continue in healthy timber because the broods fail to develop, and such outbreaks as occur are short-lived. In the southern part of the United States the three most important species of Ips are grandicolUs Eichh., caJJif/raphns Germ., and avul- ms Eichh. In the Western States confv^us Lee, emarg'matus Lee, inteqev Eichh., oi-egoni Eichh., and radiafae Hopk. are the most destructive species. /. oregonl very commonly kills the tops of matui-e western yellow^ jnnes, rendering the trees susceptible to the attack of Dendroctonus beetles (i, 4^, ^*'^- ^'■^- '^^>)- MONTEKEY CVPltESS BAUK I5EETLE Phloeosliius cristatus Lee. Several species of Phloeosinus, a genus of bark beetles, apparently are capable of killing trees belonging to those genera allied to Cupressus. This species seems to be particularly aggressive in INIonterey cvpress planted in the vicinity of San Francisco. It is usually "associated, however, with scale insects and fungi, and its specific role has not been accurately determined. THE HICKORY BARK 15EETLE Scolytvs qiiadnspino.su>i Say The hickory bark beetle is an important enemy of hickory in the Eastern States. Every feAv years local outbreaks of the liickory bark beetle destroy considerable timber in the natural range of the tree from Massachusetts southward to Georgia and westward into the Mississippi Valley. Recent studies indicate that these out- breaks are correlated with droughts or conditions unfavorably af- fecting the trees {2, J^S). THE FIB BARK BEETLE S(oliftits reniralift Lee. This species, widely distributed throughout the Western States, attacks standing dead, dying, or living firs, fre(iuently killing them but more often destroying only tlie tops of the trees or patches of bark on the trunk, Avhich results in defects. In California, following the drought of 15)'2-1, very extensive losses were reported {^0, 4^J). INSECTS BORING IN LIVING TREES THE SM.VLL MKTAl.I.IC WOOD AND BARK BORERS Agrilus anxiits Gory Af/rihis bUineatus AVeb. The bronze birch borer {Agr/hcs an.i-lu.^ Gory) is very destructive to .several species of birch (Betula) in the Nortlieast. Its control is becoming an important problem in the management of hardwood stands. The 'i-lined chestnut borer {A. hUlneatKx Web.) is of sec- ondary importance througliout the eastern part of the United States. It occasions the death of oaks weakened by other causes, though in Minnesota it is reported to be more of a primary pest (5, 7^, J/', 6u). IMPORTANT NORTH AMERirAN FOREST INSECTS 7 THK, TUKPFNTINE ROKEK Bujtrcstis ojirictDiK Hbst. The turpentine borer attacks the exposed wood resnltincr from fire scars, blazes, and turpentined faces of several species of southern pines, making the trees susceptible to windthrow, and the butt log unfit for lumber. In recent years, with the wider adoption of con- servative turpentining practices and forest management, injury by this insect is receiving greater recognition {8. 19). THE LOCUST BORKR Cyllene robiniae Forst. The locust borer frequently prevents the growth of a valuable tree, the black locust, in some regions. It occurs throughout the Eastern States and has been introduced with the host into Colorado and adjacent States {17, 29, J^l). THE OAK TWIG PKUNER ElaphUlion villosum Fab. The oak twig pruner, occurring throughout the eastern half of the Ignited States, locally causes serious damage to various hard- woods bv cutting off the branches. The pruning in this case is done by the larvae {^S). THE SUGAR MAPLE I50KEB Gl!ieohiuf< .sijccio-siix Siiy The sugar-maple borer is an especially injurious pest of the sugar maple tree in the Northeastern States. This borer attacks trees apparently in full vigor, especially those growing in the open, and kills limbs and sometimes the entire tree. This insect is probably the most serious enemy of the sugar maple tree {25) . THE LIVTtNG HICKORY BOEEB Goe-i pulcher Hald. THE LIVING BEECH BOKKR Goes pulverulenfa Halcl. THE WHITE OAK BORER Goef! tif/rina Dedeer THE OAK SAPLING BOREB r/ot'.s- te.s.sellot(i Haljl. The four species of roundheaded borers listed above attack the trunks of a variety of hardwoods, including oak, hickory, beech, elm, sycamore, blue beech, and ironwood, throughout the eastern part of the United States. The larvae bore deeply into the wood, causing large, unsightly defects and culls in the lumber. In youngo'- trees these defects frequently cause breakage under the strain of wind or ice storms {IS). 8 MISC. PUBLICATION 7 4, U. S. DEPT. OF AGRICTJLTUEB THE PINE AND HEMLOCK FLAT-HEAD BOREBS Melanophila spp. Two species of the genus Melanophila, the eastern hemlock bark borer {M. fulvoguttata Ham.) and the western flat-headed borer {M. gentilis Lee), are of considerable economic importance. The eastern form kills hemlock weakened by defoliation and other causes. The western species is frequently an important pest during epidemics of the western-pine bark beetle in western yellow pine and to trees affected by drought •(<§, Jf6). THE TWIG TUNNELER3 Oberea spp. Several species of Oberea bore down through the pith in the twigs of several species of trees and shrubs, causing the death of the infested portion. The work can always be distinguished from that of other twig girdlers by the linear series of small holes cut through the bark. 0. my ops Hald. in rhododendron and azalea, 0. schaumii Lee. in poplar, and O. trlpunctata Fab. and O. himaoulata Oliv. in plum, apple, peach, and dogwood are the most impor- tant {18). THE LONG-HORNED GIRDLER8 Oncideres cUujulata Say Oncideres putator Thom. The hickory twig girdler {Oncidei'es cingulata) and the huisache girdler {O. putator) cause considerable damage to a great variety of hardwood trees in the Eastern and Gulf States by cutting off the branches. The girdling is done by the adult beetle {18^ 37) . THE COTTONWOOD BORER Plectrodera scalator Fab. In the central part of the United States the cottonwood borer causes serious injury to the base and roots of several species of cottonwood and willow. It is sometimes abundant enough in certain localities to kill these trees {62). THE PRION ID ROOT B0RER8 Prionus spp. Several species of these large roundheaded borers — Prionus lati- Gollis Drury and P. imbricomis L. in the East, and P. calif ormou.s Motschulsky in the Western States — bore in the roots of living hardwoods, thus lowering the vitality of the trees. The attack is frequently followed by root rots such as Armellaria and attacks of secondarj'^ bark borers which ultimately kill the trees {16) . THE RED OAK BORER Romalev/m rufulutn Hald. The red oak borer is of considerable economic importance through- out its range in the central and eastern part of the United States and Canada. The habits of this species somewhat resemble those of IMPORTANT NORTH AMERICAN FOREST INSECTS 9 Prionoxystus and Goes. The borers attack living oak trees, mining deeply into the sapwood and heartwood (18). THE ELM BORER Saperda tridentata Oliv, THE LINDEN BOREB Saperda rcstita Say THE POPLAR BOREB Saperda calcarata Say The larvae of the poplar borer riddle the heartwood of several species of poplar, opening it to decay and making the trees subject to windfall. It is widely distributed throughout the range of the host plants. Several other species of this genus, among which Saperda tridentata in elm and S. vestita in linden are important, are injurious to living trees {18, 27, 38). THE WESTERN FIB BOREB Tetropmm abietis Fall In the Pacific coast region the western fir borer occasionally kills large numbers of true firs by mining beneath the bark. Trees weak- ened by defoliation or fire are particularly susceptible to attack U8). THE WESTERN LARCH BARK BOREB Tetropmm velutinum Lee. The western larch bark borer is occasionally a pest of considerable importance in stands of western larch and hemlock in the Rocky Mountain and Pacific coast regions of the United States. The larvae mine in the inner bark {18, 68). THE CEDAR POLE BORER Trachykele blondeli Mars. The larvae of the western cedar pole borer riddle the heart and sapwood of living western red cedar, causing serious defects and the consequent rejection of the damaged material for lumber, shin- gles, and poles. This borer occurs in Oregon, Washington, and California {9). THE PITCH MOTHS Dioryctria abietella D. and S. Diorycfria xanthaenobaren Dyar Dioryctria ponderosae Dyar Dioryotriu amatella Hulst The inner bark of the trunks, the new growth of the leaders, and the cones, of pine, Douglas fir, spruce, and fir are often seriously injured by the caterpillars of the pitch moths. Death of parts or even the entire tree and the loss of seed of the infested cones fre- quently follow the injury. These insects are important, but little work has been done on them. 97801°— 30 2 10 MISC. PUBLICATION 7 4, U. S. DKPT. OF AGRICULTURE THE ZIMMERMAN PIXK MOTH Pinipetitis zimtnerniani Grote The Zimmerman pine moth is a serious insect pest of pine, attack- ing \\'estern 3ellow pine, white pines, Scotch pine, and Austrian pine. The caterpillar bores into the bark of the trunk, usually avoiding the base and top. and causes the malformation known as spike top or sometimes kills the entire tree. The injury it produces also brings about a considerable depreciation in the value of the timber. Tlic species is especially abundant in the northern and west- ern part of the United States (6). THE CARPENTER WORM Priono-riistus robitiiae Peek The lar\ae of this large moth bore in a great variety of eastern hardwoods, especially oak and locust, causing large wormholes and resulting defects in the lumber {44, 4^). THE DOUGLAS FIR PITCH MOTH 8ynt. 2. 95 p.. illus. (61) 1926. PREVENTING DAMAGE BY LYCTUS POWDER-POST BEETLES. U. S. Dept. Agr. Farmers' Bul. 1477. 12 p., illus. (62) 1927. DKFKCTS IN TIMBER CAl SF.D BY INSECTS. U. S. Dept. A.L^r. Bul. 1490. 47 p., illus. (63) SWAINE. .J. M. 1918. CANADIAN BARK BEETLES. II. A PRELIMINARY CLASSIFICATION WITH AN ACCOUNT OF THE HABITS AND MEANS OF CONTROL. Canada Dept. Agr. Ent. Branch Bul. 14 (pt. 2), 143 p., illus. (64) Craighead, F. C, and Bailey'. I. W. 1924. STUDIES ON the spruce BUDWORM. (CACOECIA FUMIFERANA CLEM.). Canada Dept. Agr. Ent. Branch Bul. (n. s.) 37, 91 p., illus. (65) SwENK. M. H. 1927. the PINE TIP MOTH IN THE NEBRASKA NATIONAL FOREST. Nebr. Agf. Expt. Sta. Research Bul. 40. 50 p., ilUis. (66) Trimble, F. M. 1924. lite history- and habits of two pacific coast bark beetles. Ann. Ent. Soc. Amer. 17: 382-[391], illus. (67) WEBB, J. L. 1909. SOME INSECTS INJURIOUS TO FORESTS. IV. THE SOUTHERN PINE SAWYER. T'. S. Dept. Aar., Bur. Ent. Bul. 58. pt. 4. p. 41-56. illus. (68) 1911. IN.IURIES TO FORESTS AND FOREST PKODUCTS BY KOUNUHEADED BORERS. U. S. Dept. Agr. Yearbook 1910:341-358, illus. ADDENDA Most of the papers cited below were published subsequent to the preparation of this one. ((!$») Allison, J. H., and Orb, L. W. 1929. A NEW MENACE TO SCOTCH AND JACK PINE. JOU)'. Foi'. 27: 821-S24. (70) .\NNAND, P. N. 1925. A CONTRIBUTION TOWARD A MONOGRAPH OF THE ADELGINAE (PHYI.LOX- eridae) OF NORTH AMERICA. Stanford Univ. Pubs.. Biol. Sci. vol. 6, no. 1, 146 p. (71) BuscK, A. 1915. THE EUROPEAN PINE-SHOOT MOTH ; A SERIOUS MENACE TO PINE TIM- BER IN AMERICA. U. S. Dept. Agr. Bul. 170, 11 p., illus. (72) DixisiON OF Forest Insect Investigations, bureau of entomology. 1927. THE RELATION OF INSECTS TO SLASH DISPOSAL. U. S. Dept. Agr. Dept. Circ. 411, 12 p. (73) Friend, R B. 1926. the spruce call aphid (adelges abietis l.) and its control. Conn. Agr. Expt. Sta. Rpt Bul. 285, p. 223-228. (74) 1927. THE BIOLOGY OF THE BIRCH LEAF 8KELETONIZEB BUCCAL.\TRIX CAN ADKNSiSEi-LA, CHAMBERS. Conn. Agr. Expt. Sta. Bul. 288: [305]- 486. illus. IMPORTANT NORTH AMERICAN FOREST INSECTS 27 (To) Keen, F. P. 1920. TUSSorK MOTH MKNACE. Tiinbowder post beetle (88) ; the red shouldered powder post beetle (84) ; termites (87) ; the spruce twig gall lice (70, 73. 80) ; the pine bark louse (80) ; the white pine weevil (76) ; the European pine shoot moth (71) ; the pine soft Koales {(!!)) : the birch leaf skeletonizer (74) : the larch case bearer (82) : the Pandora moth (SI) ; the Douglas fir tussock moth (7J) ; the birch leaf inliiei" (83). INDEX Page Acorn gall makers 16 Adelges abietis 15 Adelges cooleyi- 15 Agrilus anxius 6 Agrilus bUineatus.. 6 Agromyza aceris 10 Agromyza amelanchieris 10 Ambrosia beetles 11 Anisotarubicunda 18 Anisota sanatoria 18 Anisota stigma IS Anisota virginiensis.. 18 Apatides fortis 14 Argyrotaenia pinatubana. 20 Banded ash borer. 13 Belted chion 12 Birch leaf miner. — - 23 Birch leaf skeletonizer 18 Black Hills beetle. ,. 5 Black-horned pine borer 12 Black turpentine beetle.. 4 Bronze birch borer. 6 Brown-tail moth 20 Bucculatrii canadensisella 18 Buprestis apricans.. 7 Cacoecia fumiferana.. 18 California oak worm_. 21 Callidium antennatum... 12 Cambium miners.. 10 Camponotus herculeanus pennsylvanicus 14 Carpenter ant 14 Carpenter worm 10 Catalpa sphinx 19 Cedar pole borer 9 Cedar-tree borer.. 12 Ceratomia catalpae.. 19 Chalepus dorsalis 18 Cheilosa alaskensis 11 fChermes) Adelges abietis 15 (Chermes) Adelges cooleyi 15 (Chermes) Pineus pinicorticis 16 Chestnut timber worm 11 Chionaspis pinifoliae 17 Chion cinctus 12 Colaspis brunnea. 18 Coleophoralarlcella.. 19 Coloradia pandora 19 Columbian timber beetle 11 Cone beetles 15 Conophthorus coniperda 15 C onophthorus lambert ianae 15 Conophthorus ponderosae 15 Conophthorus spp 15 Corythlus columbianus 11 Cottonwood borer. 8 Curculio spp.. 15 Cyllene caryae.. 12 Gyllene robiniae 7 Cynipidae 16 Cypress bark scale 17 Datana integerrima 19 Datana ministra 19 Dendrobiella aspera 14 Dendroctonus barberi 5 Dendroctonus brevicomis. 5 Dendroctonus engelmanni 20 Dendroctonus frontalis 4 Dendroctonus jeffreyi 5 Dendroctonus monticolae 4 Dendroctonus piceaperda. 4 Dendroctonus ponderosae 5 Dendroctonus pseudotsugae 5 Dendroctonus terebrans 4 Dendroctonus valens 4 Dioryctriaabietella 9 Dioryctria amatella 9 Dioryctria ponderosae 9 Dioryctria lanthaenobarea 9 Page Douglas fir beetle 5 Douglas fir chalcid 16 Douglas fir looper.. 19-20 Douglas fir pitch moth 10 Douglas fir tussock moth 20 Eastern hemlock bark borer... 8 Eastern spruce beetle 4 Eastern white pine cone beetle 15 Ehrhornia cupressi. 17 Elaphidion villosum 7 EUopia flscellaria 19 Elloplasomniaria.- 19 Ellopiaspp 19 Elm borer 9 Engelmann spruce beetle.. 20 Engraver beetles 5-6 Eupsalis minuta 11 European pine shoot moth 17 Fir bark beetle 6 Flat oak borer 14 Galenarasp 19-20 (Gillettea) Adelges cooleyi 15 Gipsy moth _ 21 Glycobius speciosus 7 Goes pulcher 7 Goes pulverulenta 7 Goes tp,ssellata 7 Goes tigrina 7 Grape colaspis.. 18 Gray ash borer 13 Green-striped maple worm 18 Hemerocampa pseudotsugata 20 Hemicallidium amethystinum... 12 Hemlock bark maggot 11 Hemlock budworm 21 Hemlock loopers 19 Heterocampa bilineata 20 Heterocampa biundata 20 Heterocampa guttivitta 20 Heterocampa manteo 20 Heterocampa spp 20 Hickory bark beetle. 0 Hickory twig girdler 8 Huisache girdler 8 Hylecoetus lugubris... 11 Hylobius pales 16 Hylotrupes hajulus .. 12 (Hylotrupe^) Hemicallidium amethystinu.u. 12 Hylotrupes ligneus 12 Ips avulsus 6 Ips calligraphus 6 Ips confusus . 6 Ips emarginatus 6 Ips grandicollis-. 6 Ips integer 6 Ips spp... 5-fi Jeffrey pine beetle 5 Kalotermes spp 14-15 Larch case-bearer 19 Larch sawfly 22 Lead-cable borer. 14 Leopard moth 10 Linden borer 9 Living beech borer 7 Living hickory borer 7 Locust borer 7 Locust leaf miner 18 Lodgepole needle tier 20 Lodgepole sawfly... 20, 22 Long-horned girdlers 8 Lyctus planicoUis 14 Lyctus spp... 14 (Ljmexylon) Melittomma sericeum.. il Malacosonia anieiicana -'I Malacosoma californica — 21 Malacosoma coiistricta ^1 Malacosoma disstria.. 21 Malacosoma fragilis 21 29 / 30 MISC. PUBLICATION 7 4, U. S. DEPT. OF AGRICULTURE Page Malacosoma pluvialis 21 Maple defoliators - -.- 20 May beetles 'fi Megastigmus alhifrons l*> Megastigmiis milleri 16 Megastigmns piceae - -- -- IG Megastigmus pinus 16 Megastigmus spermatrophus 16 Melanophila fulvoguttata - 8 Melanophila gentilis_ 8 Melittomma sericeum 11 Monoehamus confusor._ 13 Monochamus maculosiis... _ 13 Monochamus marmorator _ 13 Monochamus scutellatus 13 Monochamus spp _ 13 Monochamus titillator 13 Monterey cypress bark beetle -.- 6 Mountain pine beetle 4 Nantucket pine moth 17 Nematus erichsonii - 22 Neoclj'tus capraea.- 13 Neoclytus conjunctus -. 13 Neoclytus erythrocephalus. 13 Nendiprion banksianae 22 Neodiprion excitans 22 Neodiprion lecontei.. 23 Neodiprion scutellaris 22 Neodiprion spp 20,22 Neophasia menapia 21 Nut weevils -- .- 15 Nygmia phaeorrhoea 20 Oak and maple defoliators 20 Oak sapling borer 7 Oak timber worm... - 11 Oak twig pruner 7 Oberea bimaculata 8 Oberea myops 8 Oberea schaumii --- 8 Oberea spp.. 8 Oberea tri punctata 8 Old-house borer 12 Oncideres cingulata - -. 8 Oncideres putator 8 Orange-striped oak worm_ 18 Painted hickory borer... 12 Pales weevil 16 Pandora moth. 19 Parandra brunnea 13 Peronea variana.. 21 Phloeosinus cristatus 6 Phryganidia californica 21 Phyllophaga spp 16 Phyllotoma nemorata 23 Phymatodes variabilis 13 Pine bark louse 16 Pine butterfly 21 Pine needle miner 22 Pine needle scale 17 Pine sawyers 13 Pine soft scales 17-18 Pineus pinicorticis 16 Pinhole borers. 11 Pinipestis zimmermani 10 Pissodes strobi 16-17 Pitch moths. {See Dioryctria spp., Douglas flr pitch moth, and sequoia, pitch moth.) Plectrodera scalator.. 8 Pole borer 13 Poplar borer 9 Porthetria dispar. 21 Pag« Powder-post beetles (see alto red-shouldered powder-post beetle) 14 Prionid root borers.. 8 Prionoxystus robiniae 10 Prionus californicus 8 Prionus Imbricornis 8 Prionus laticollis 8 Prionus spp 8 Recurvaria milleri 22 Red-headed ash borer 13 Red-headed pine sawfly 23 Red oak borer f' Red-shouldered powder-post beetle 14 Red turpentine beetle 4 Reticulitermes spp 15 Rhyacionia buoliana 17 Rhyacionia frustrana 17 Romaleum rufulum 8 Saperda calcarata 9 Saperda tridentata. 9 Saperda vestita 9 Sapwood timber worm 11 Satin moth 22 Sawflies 22 Scobicia declivis 14 Scolytus quadrispinosus 6 Scolytus ventralis fi Seed ehalcids 16 Sequoia pitch moth 10 Small metallic wood and bark borers 6 Smodicum cucujiforme 14 Southern pine beetle 4 Southwestern pine beetle 5 Spiny oak worm : 18 Spruce hud worm 18 Spruce twig gall lice ^ 15 Stilpnotia salicis.. 22 Sugar maple borer 7 Sugar pine cone beetle.. l.'i Synanthedon novaroensis 0 Tanbark borer 13 Tent caterpillars 21 Termites (nonsubterranean) 14-15 Termites (subterranean) 15 Tetropium abietis 9 Tetropium velutinum 9 Toumeyella numismaticum 17-18 Toumeyella parvicorne.. 17 Toumeyella pini 17 Toumeyella spp.. 17 Trachykele blondeli 9 Turpentine beetles 4 Turpentine borer 7 Twig tunnelers 8 Two-lined chestnut borer 6 Vespamima sequoiae 10 Walnut caterpillar 19 Western cedar bark borer 12 Western fir borer 9 Western flat-headed borer 8 Western larch bark borer 9 Western pine beetle 5 White grubs -- 16 Whiteoak borer. 7 White pine weevil 16-17 Xylobiops basilare 14 Yellow-necked caterpillar 19 Yellow pine cone beetle 15 Zeuzera pyrina 10 Zimmerman pine moth IC ORGANIZATION OF THE UNITED STATES DEPARTMENT OF AGRICULTURE May 1. 1930 Serretnry of Agriculiure Arthur M. Hyde. Assist ant Secretary R. W. Dunlap. Director of Scientific Work A. F. Woods. Director of Regulatory Work Walter G. Campbell. Director of Extension Work C. W. Warburton. Director of Personnel and Business Adminis- W. W. Sto('KBERGbr. tration. Director of Information M. S. Eisenhower. Solicitor E. L. Marshall. Weather Bureau Charles F. Marvin, Chief. Bureau oj Animal Industry John R. Mohler, Chief. B^ireau of Dairy Industry O. E. Reed, Chief. Bureau of Plant Industry William A. Taylor, Chief. Forest Service R. Y. Stuart, Chiej. Bureau of Chemisfri/ and Soils IT. G. Knu;ht, Chief. Bureau oj Entomology C. L. Marlatt, Chief. Bureau of Biological Survey Paul G. Redington, Chief. Bureau of Public Roads Thomas H. MacDonald, Chief. Bureau of Agricultural Economics Nils A. Olsen, Chief. Bureau of Home Economics Louise Stanley, Chief. Plant Quarantine and Control Administration. Lee A. Strong, Chief. Grain Futures Administration J. W. T. Duvel, Chief. Food, Drug, and Insecticide Administration.. Walter G. Campbell, Director of Regulatory Work, in Charge. Office oj Experiment Stations , Chiej. Office oj Cooperative Extension Work C. B. Smith, Chief. Library Claribel R. Barnett, Librarian. This puy^lication is a contribution from Bureau of Entomology C. L. Marlatt, Chief. Division of Forest Insects F. C. Craighead, Principal Ento- mologist, in Charge. 31 B. S. GOVERNMENT PRINTINS OFFICEl 1939 For snip by the Superintendent of Documents. Washington, D. C. ----- - Prico 10 cents U. S. DEPARTMENT OF AGRICULTURE, BUREAU OF ENTOMOLOGY— BULLETIN No. 58, Part V. L. O. HOWARD, Entomologist and Chief of Bureau. SOME INSECTS INJURIOUS TO FORESTS. INSECT DEPREDATIONS IN NORTH AMERICAN FORESTS AND PRACTICAL METHODS OF PREVENTION AND CONTROL. BY A. D. HOPKINS, Ph. D., In Charge of Forest Insect Investigations, Issued December 4, 1909. WASHINGTON: GOVERNMENT PRINTING OFFICE, 1909. BUREAU OF ENTOMOLOGY.'^ L. O. HoWAKD, Entomologist and Chief of Bureau. O. L. Marlatt, Assistant Entomologist and Acting Chief in Absence of Chief. R, S. Clifton, Executive Assistant. Chas. J. GiLLiss, Chief Clerk. F. H. Chittenden, i/i charge of truck croi) and stored product insect investigations. A. D. Hopkins, in charge of forest insect investigations. W. D. Hunter, in charge of southern field crop insect investigations. F. M. Webster, in charge of cereal and forage insect investigations. A. L. QuAiNTANCE, in charge of deciduous fruit insect investigations. FJ. F. Phillips, in charge of bee culture. D. M. Rogers, in charge of preventing spread of moths, field tvork. RoLLA P. Currie, in charge of editorial tvork. Mabel Colcord, librarian. Forest Insect Investigations. A. D. Hopkins, in charge. n. E. BuBKE, J. L. Webb, Josef Brunner, S. A. Rohwer, T. E. Snyder, W. N. Dovener, agents and experts. Mary E. Faunce, preparator. William Middleton, student assistant. W. D. Edmonston, forest ranger, detailed from Forest Service. " Organization of the Bureau on November 1, 1909. LETTER OF TRANSMITTAL. U. S. Department of Agriculture, Bureau or Entomology, Washington^ D. C.^ August 23, 1909. Sir : I have the honor to transmit herewith, and to recommend for publication as Bulletin No. 58, Part V, of the Bureau of Ento- mology, manuscript of a paper by Dr. A. D. Hopkins, in charge of forest insect investigations of this Bureau, entitled "Insect Depre- dations in North American Forests and Practical Methods of Pre- vention and Control." The paper is based largely on the observations and experience of the author and of the assistants engaged in forest insect investiga- tions, and contains a list of publications relating to forest insects. Respectfully, L. O. Howard, Entomologist and Chief of Bureau. Hon. James Wilson, Secretary of Agriculture. CONTENTS. Page. Introduction 57 Insect depredations in North American forests 57 Character and extent of depredations 57 Insects cause the death of trees 58 The southern pine beetle 58 The eastern spruce beetle 58 The Engelmann spruce beetle 59 The Black Hills beetle 59 The mountain pine beetle and the western pine beetle 59 The Douglas fir beetle 59 The hickory barkbeetle 60 The larch worm 60 Insect injuries to the wood of living trees 60 The oak timber worm 60 The chestnut timber worm 60 Carpenter worms 61 Ambrosia beetles 61 The locust borer 61 Turpentine beetles and turpentine borers 61 The white pine weevil 62 Insect injuries to the wood of dying and dead trees 1 62 Coniferous trees 63 Sawyers 63 Ambrosia beetles 63 Pinhole borers in cypress 63 Hardwood trees 64 Round-headed borers, timber worms, and ambrosia beetles.. 64 Insect injuries to forest products. 64 Crude products 64 Round-headed borers, timber worms, and ambrosia beetles.. 64 Manufactured unseasoned products 65 Ambrosia beetles and other wood borers 65 Seasoned products in yards and storehouses 66 Powder-post beetles 66 Finished products 66 Utilized products 66 Powder-post beetles, white ants, and other wood-boring in- sects 66 Insects in their relation to the reduction of future supplies of timber 67 Interrelations of forest insects and forest fires 67 Losses from forest insects 67 Insect-killed timber as fuel for fires 68 Fire-killed timber injured by insects 68 V VI CONTENTS. Insect depredations in North American forests— Continued. Interrelations of forest Insects and forest fires— Continued. Page. Destruction of insects by fire 68 Durability of insect-killed timber - - 69 Interrelation of forest insects and forest fungi 69 Decay following injury by insects 69 Summary and estimates relating to character and extent of insect damage. 69 Standing timber killed and damaged by insects 70 Keduction in the Nation's wealth 71 Reduction in cash revenue 71 Reduction in value of finished and commercial products 71 Methods of prevention and control 71 General principles of control 72 Control of barkbeetles which kill trees 73 Maintaining control of barkbeetles 74 Examples of successful control of barkbeetles 75 Control of insects which cause defects in living timber 78 Prevention of injury to dying and dead trees 78 Prevention of loss from insect injuries to natural and artificial reproduction. 79 Utilization of immune and resistant varieties and races of trees 79 Prevention of insect injuries to forest products 79 Crude products 79 Manufactured products 81 Unseasoned products 81 Seasoned products 81 Past and present conditions of powder-post injury 82 Tan bark 83 Utilized products 83 Timbers and woodwork in structures — 83 Utilization of natural enemies and factors in the control of injurious insects 85 Beneficial insects 86 Beneficial diseases of insects 86 Beneficial birds 86 Beneficial climatic conditions 87 Utilization of waste caused by insects 87 Present conditions and opportunities 88 Forest entomology as applied to American forests 88 Present knowledge 88 Needs 89 Elementary and technical knowledge of forest entomology for the forester 91 Present requirements of instruction 91 Conclusion 91 General estimates of amount of damage caused by forest insects 92 How losses can be prevented 93 Publications relating to forest insects 96 Historical and general 96 Prepared by officials of the branch of Forest Insect Investigations, Bureau of Entomology, and of the West Virginia Agricultural Experiment Station 97 Publications relating to forest statistics 100 Forest resources 100 Forest fires 101 U. S. D. A., P.. E. Bill. 5S. Tart V. F. I. I., December 4, 1, 1903Z>, 1909/>.) The eastern spruce heetle. — During the period betAveen 1818 and 1900 there were several outbreaks of the eastern spruce beetle {Den- droctonus piceaperda Hopk.) in the spruce forests of- New York, New England, and southeastern Canada (Peck, 1876, 1878; Hough, 1882: Packard, 1890: Pinchot, 1899, p. 74: Hopkins, 1901^, 1909&). INSECT DEPEEDATIONS IN NOETH AMERICAN FORESTS. 59 This species caused the death of a very large percentage of the ma- ture spruce over an area of thousands of square miles. In the aggre- gate many billions of feet of the best timber were destroyed. The larger areas of this dead timber furnished fuel for devastating for- est fires, with the result that in most cases there was a total loss. The Engelmann spruce beetle. — Another barkbeetle {Dendrocto- nus engelmanni Hopk.), similar in habits to pkeaperda^ has from time to time during the past fift}^ years caused widespread devasta- tions in the Rocky Mountains region to forests of Engelmann spruce, in some sections killing from 75 to 90 per cent of the timber of mer- chantable size. (Hopkins, 1908rt, p. 161; 1909^, pp. 126-132.) The Black Hills beetle. — One of the most striking examples of the destructive powers of an insect enemy of forest trees is found in the Black Hills National Forest of South Dakota, where during the past ten years a large percentage of the merchantable timber of the entire forest has been killed by the Black Hills beetle {Dendroctonus pon- derosa' Hopk.). It is estimated that more than a billion feet of timber have been destroyed in this forest as the direct result of the work of this beetle. This destructive enemy of the western pine is distributed throughout the forests of the middle and southern Rocky Mountains region, where, within recent years, it has been found that in areas of greater or less extent from 10 to 80 per cent of the trees have been killed by it. (Hopkins, 1902«, 19036, 19056, 1908a, and 19096, pp. 90-101.)" The mountain pine beetle and the western pine beetle. — The sugar pine, silver pine, western yellow pine, and lodgepole pine of the region north of Colorado and Utah, westward to the Cascades, and southward through the Sierra Xevadas are attacked by the mountain pine beetle {Dendroctronus monticolce Hopk.) and the western pine beetle {Dendroctonus brevicomis Lee), and, as a direct consequence, billions of feet of the timber have died. In one locality in north- eastern Oregon it is estimated that 90 to 95 per cent of the timber in a dense stand of lodgepole pine covering an area of 100,000 acres has been killed within the past three years by the mountain pine beetle. Throughout the sugar-pine districts of Oregon and California, as the result of attacks by this same destructive barkbeetle, a considerable percentage of the largest and best trees is dead. (Webb, 1906; Hop- kins, 1908«, 19096, pp. 80-90.) The Douglas fr beetle. — The Douglas fir throughout the region of the Rocky Mountains from southern New Mexico to British Co- lumbia has suffered severely from the ravages of the Douglas fir beetle {Dendroctonus pseudotsugw Hopk.), with the result that a large percentage of dead timber is found, much of which will be a total loss. (Hopkins, 19096, pp. 106-114.) Three other species of beetles, having destructive habits similar to those above mentioned, depredate on the pines of New Mexico 12877— Bull. 58, pt 5—09 2 60 SOME INSECTS INJURIOUS TO FORESTS. and Arizona, and still another has contributed greatly to the de- struction of the larch throughout the northeastern United States and southeastern Canada. (Hopkins, 19096, pp. 49, 53, and 77.) The hicl-ovy harkheetl e.—W'iihm the past ten years the hickory oarkbeetle {Seohjtus quadrispinosus Say) has caused the destruction of an enormous amount of hickory timber throughout the northern tier of States from Wisconsin to Vermont and southward through the eastern Atlantic States and into the Southern States as far as central Georgia. (Hopkins, 1904&, pp. 314-317.) The larch worm. — There are also many examples of widespread depredations chargeable to insects which defoliate the trees, thus contributing to their death. Notable among these are the depreda- tions by the larch Avorm {Nemattis erichsonii Hartig), which, during several extensive outbreaks since 1880, has killed from 50 to 100 per cent of the mature larch over vast areas in the northeastern United States and southeastern Canada. It is evident that the amount of merchantable-sized timber that has died as the result of defoliation by this insect will aggregate many billions of feet. (Packard, 1890, pp. 879-890; Pinchot, 1899; Hopkins, 1908^.) Insect Injuries to the AVood of Living Trees. It has been determined that insects of a certain class attack the wood and bark of living timber and that, while they do not con- tribute materially to the death of the trees or give much external evidence of their presence, the}^ produce wounds in the bark and wormhole and pinhole defects in the Avood Avhich result in a depre- ciation in commercial value amounting to from 5 to 50 per cent. These defects in the wood are not detected until after the trees have been felled and the logs transported to the mill and con\^erted into lumber. Thus to the actual damage to the lumber is added the expense of logging and manufacture of the defectiA-e, low-grade ma- terial, much of Avhich must be discarded as Avorthless culls. (Hop- kins, 1894a, 1894&, 19046, 1905«, 19066.) The oal' timher vu)rm. — One of the most destructive of the class of depredators just mentioned is the oak timber Avorm {Eupsalis miriuta Dru.). It enters the Avood of the trunks of living trees through Avounds in the bark and at the base of broken or dead branches and extends its "pinhole" burrows in all directions through the solid heartAvood. The losses occasioned by this insect in the hardwood forests of the eastern United States are enormous and usually affect the wood of the finest examples of old trees. (Hopkins, 1894«, 19046.) The chestnut timher rcor/n.— The chestnut throughout its range is damaged in a like manner by the chestnut timber worm {Lymexylon sericexivi Harr.). Practically every tree of merchantable size is INSECT DEPEEDATIONS IN NOETH AMERICAN FORESTS. 61 more or less affected, and a lai'tre percentage is so seriously damaged that the product is reduced to that of the lowest grade. It is esti- mated that the reduction in value of the average lumber product at any given time is not far from 30 per cent, thus involving extensive waste and an increased drain on the forest to supply the require- ments for clear lumber. This insect also attacks the oaks, and especially the red oak, the older trees of which are often as seri- ously damaged as are the chestnut. (Hopkins, 189-t«, 1904&.) Carpenter toorms. — The oaks, especially the white oak and the red oak, are seriously damaged by carpenter worms of the genus Prion- oxystus. The holes made by these insects through the heart wood of the best part of the trunks are sometimes 1.5 inches in diameter one way by 0.75 inch the other, thus causing serious damage to the wood. These, with other large wood-boring beetle larvae, sometimes infest the top part of the trunk and the larger branches of oak trees, where their continued work results first in the dead and so-called " stag- horn " top and subsequently in broken, decayed, and worthless trunks. (Hopkins, 1894a, 19045.) Ambrosia beetles. — One of the commonest defects in white oak, rock oak, beech, whitewood or yellow poplar, elm, etc., is that known to the lumber trade as " grease spots,'' " patch worm," and " black holes." This defect is caused by one of the timber beetles or ambrosia beetles, Corthyhis col/iimhianus Hopk., which makes successive attacks in the living healthy sapwood from the time the trees are 20 or 30 years old until they reach the maximum age. Thus the black-hole and stained-wood defect is scattered all through the wood of the best part of the trunks of the trees. The average reduction in value of otherwise best-grade lumber amounts, in many localities, to from 25 to 75 per cent. The defect is commonly found in oak and elm furniture and in interior hardwood finish in dwellings and other buildings. (Hopkins, 1893(7, 18945, 19045.) The locust borer. — The locust, as is well known, suffers to such an extent from the ravages of the locust borer {Cyllene robince Forst.) that in many localities the trees are rendered worthless for commercial purposes or they are reduced in value below the point of profitable growth as a forest tree, otherwise this would be one of the most profit- able trees in the natural forest or artificial plantation and would con- tribute greatly to an increased timber supply. (Hopkins, 19065, 1907rt, 1907r.)' Turpentine beetles and turpentine borers. — While the softwood trees, or conifers, suffer far less than the hardwoods from the class of enemies which cause defects in the living timber there are a few notable examples of serious damage. There is a common trouble affecting the various species of pine throughout the country known as basal wounds or basal fire wounds. It has been found that a large 62 SOME INSECTS INJURIOUS TO FORESTS. percentage of this injury to the pine in the States north and west of the Gulf States and in the Middle and South Atlantic States is caused bv the red turpentine beetle {Dcndrocfonus miens Lee.) and in the Southern States by the black turpentine beetle {Dendroctonus terebrans Oliv.). These beetles attack the healthy living bark at and toward the base of the trunks of medium to large trees and kill areas varying in size from 1 to 10 square feet. These dead areas are sub- sequently burned off by surface fires and are then generally referred to as fire-wounds. The further damage to the exposed wood by successive fires, decay, and insects often results in a total loss of the best portion of the tree, or a reduction in value of the lower section of the trunk of from 10 to 50 per cent. (Hopkins, 190-tff, 1909&.) These and similar wounds in the bark of trees, including those caused b}' lightning and by the uncovering and exposure of the wood in tur- pentining, offer favorable conditions for the attack of the turpentine borer {Buprestis aprkans Hbst.), the work of which, together with that of two or three others with similar habits, is very extensive, and causes losses amounting to from 10 to 50 per cent of the value of the wood of the best part of the trees thus affected. (Hopkins lOOla.) The white pine weevil. — The abnormal development of white pine trees as the result of succesive attacks on the terminals of the sap- lings and young trees by the white pine weevil {Pissodes strobi Peck) is an element of loss of considerable importance, especially in mixed stands and in open pure stands of this timber. The value of such trees is reduced from 20 to 50 per cent below those of normal develop- ment, and there is an additional loss from the effect of their spread- ing branches or crowns in the suppression or crowding out of trees which would otherwise occupy the space thus usurped. (Hopkins, 1906c, 1907^.) There are many other examples of insects which damage the wood and bark of living trees, but those mentioned should be sufficient to demonstrate the importance of insects in this relation. Insect Injuriks to the Wood of Dying and Dead Trees. Timber dying from insect attack and other causes, including fire, disease, storms, etc., is attacked by certain wood-boring insects which extend tl.'eir burrows through the sound sapwood and heartwood, and thus contribute to the rapid deterioration and decay of a com- modity which otherwise would be available commercially during periods of from one to twenty years or more after the death of the trees, depending on the species of trees and on the character of the product desired. This loss often amounts to from 25 to 100 per cent during the period in which the dead timber would otherwise be almost as valuable as if living. (Hopkins, 1894a, 1901<:/, 1904a, 1905« ; Webb, 1909.) INSECT DEPEEDATIONS IN NORTH AMERICAN FORESTS. 63 CONIFEROUS TREES. Sawyers. — One of the most striking examples of the destruction or deterioration of the wood of dying and dead timber, familiar to all lumbermen, is the injury to fire-killed and storm-felled pine, fir, spruce, etc., caused by boring larvae known as " sawyers." These borers hatch from eggs deposited by the adult beetles in the bark of the dying trees, and after feeding on the inner bark for a time they enter the solid wood and extend their large burrows deep into the heartwood. Fire-killed white pine is especially liable to this injury, and is often so seriously damaged within three or four months dur- ing the warm season as to reduce the value of the timber 30 to 50 per cent. The shortleaf, loblolly, and longleaf pines of the Southern States are damaged to a somewhat less extent, but instances are known in which more than one billion feet of storm-felled timber within limited areas were reduced in value 25 to 35 per cent within three months after the storm. (Webb, 1909.) The fire-killed and insect-killed sugar pine, silver pine, and yellow pine of the western for- ests are also damaged in a similar manner and the value of the prod- uct greatly reduced within a few months after the trees die. The aggregate losses from this secondary source in the coniferous forests of the entire country contribute largely to the annual waste of mil- lions of dollars' worth of forest products which otherwise might be utilized. (Hopkins, 1905«, p. 385; Webb, 1909.) Amhrosia heetles. — Wood-boring insects of another class, known as timber beetles or ambrosia beetles, cause pinhole defects, principally in the sapwood, although some of them extend their burrows into the heartwood. These insects make their attack in the early stage of the declining or dying of the tree, or before the sapwood has materially changed from the normal healthy condition, and often in such num- bers as to perforate every square inch of wood. Thus the wood is not only rendered defective on account of the presence of pinholes, but the holes give entrance to a wood-staining fungus which causes a rapid discoloration and produces still further deterioration of the product. The sapwood of trees dying from the attack of other insects or from fire, storm, or other causes is often reduced in value 50 per cent or more, and in some cases the value of the heartwood is reduced in a like manner from 5 to 10 per cent. (Hopkins, 1894tf, 18956', 18986, 1904«, 1905«.) Pinhole ho7'ers in cypress. — An example of the destructive work of insects which attack dying and dead trees is found in the cypress in the Gulf States, where these trees are deadened by the lumbermen and left standing several months, or until the timber is sufficiently dry to be floated. Upon investigation it was found that trees dead- 04 SOME INSECTS INJURIOUS TO FORESTS. ened at certain seasons of the year were attacked by the ambrosia beetles or pinhole borers, and that in some cases millions of feet of timber had been reduced 10 to 25 per cent or more in value. (Hop- kins, 19076.) HARDWOOD TREES. Roundheaded hovers^ timber worms, and ambrosia beetles. — The principal damage to dying and dead hardwood trees is caused by cer- tain roundheaded wood-borers (Cerambycidse) with habits similar to the sawyer, by the timber worms mentioned as damaging living timber, and by ambrosia beetles having habits similar to those that attack the sapwood and heartwood of conifers. All of the hardwoods suffer more or less, but the greatest damage is done to the wood of hickory, ash, oak, and chestnut, which are often reduced in value 10 to 25 per cent or more within the period in which it would otherwise remain sound and available for commercial purposes. (Hopkins, 1894a, 1904a, 1905a.) Insect Injuries to Forest Products. Damage is caused by various species of insects which are attracted by the varying conditions prevailing at different stages during the process of utilizing the forest resources, from the time the trees are felled until the logs are converted into the crude and finished product and until the latter reaches the final consumer, or even after it is placed in the finished article or structure. As a result, additional drains are made on the timber to meet the demand for the higher grades of lumber and for other supplies to replace those injured or destroyed. From the writer's personal investigations of this subject in different sections of the country it is evident that the damage to forest products of various kinds from this cause is far more extensive than is generally recognized. This loss differs from that resulting from insect damage to standing timber in that it represents more directly a loss of money invested in material and labor. (Hopkins, 1894a, 19036', 1904a, 1905a.) CRUDE PRODUCTS. Roundheaded borers, timber woiins, and ambrosia beetles. — Round timber with the bark on, such as poles, posts, mine props, sawlogs, etc.. is subject to serious damage by the same class of insects as those mentioned under injury to the wood of dving and dead trees. The damage is especially severe when material is handled in such a man- ner as to offer favorable conditions for attack (Hopkins, 1905a), as when the logs are left in the woods on skidways or in mill yards for a month or more after they have been cut from the living trees. Under such conditions there is often a reduction in value of from 5 to 30 per cent or more, due to wormhole and pinhole defects caused by INSECT DEPREDATIONS IN NORTH AMERICAN FORESTS. 65 roundheaded and flatheaded wood-borers and timber beetles. Fre- quently the insects continue the work in the unseasoned and even dry lumber cut from logs which had been previously infested. They also continue to work in mine props after they have been placed in the mine, and in logs and other material used for the construction of cabins, rustic houses, etc., and in round timbers generally. The products from saplings, such as hickory hoop-poles and like material, are often seriously injured or rendered worthless by round- headed and flatheaded borers and wood-boring beetles, sometimes resulting in a loss of from 50 to 100 per cent of the merchantable product. (Hopkins, 1905a.) Stave and shingle bolts left in moist, shady places in the woods or in close piles during the summer months are often attacked by ambrosia beetles and timber beetles. The value of the product is often reduced, as a consequence, from 10 to 50 per cent or more. (Hopkins, 1894ff, 1905«.) Handle and wagon stock in the rough is especially liable to injury by ambrosia beetles and roundheaded borers. Hickory and ash bolts from which the bark is not removed are almost certain to be greatly damaged if the logs and bolts cut from living trees during the winter and spring are held over for a few weeks after the middle of March or first of April. (Hopkins, 1905a.) Pulpwood, and cordwood for fuel and other purposes, cut during the winter and spring and left in the woods for a few weeks or months or in close piles after the beginning of the warm weather, are sometimes riddled with wormholes or converted into sawdust borings, causing a loss of from 10 to 100 per cent. One example reported from near Munising, Mich., represents a loss of $5,000 from injury to spruce and fir pulpwood cut in the winter and kept in piles over summer. MANUFACTURED UNSEASONED PRODUCTS. Ambrosia beetles and other ivood boilers. — Freshly sawed hard- wood placed in close piles during warm, damp weather during the period from June to September is often seriously injured b}^ am- brosia beetles. Heavy 2-inch to 3-inch stuff is alio liable to attack by the same insects, even in loose piles. An example of this was found in some thousands of feet of mahogany lumber of the highest grade, which had been sawed from imported round logs and piled with lumber sticks 'between the tiers of plank. Native species of ambrosia beetles, principally Pterocyclon mali Fitch, had entered the wood to such an extent as to have reduced the value 50 per cent or more within a few weeks. Oak, poplar, gum, and similar woods often suffer severely from this class of injury, causing losses vary- ing from 5 to 50 per cent. (Hopkins, 1905a.) 66 SOME INSECTS INJURIOUS TO FORESTS. Lumber and square timbers of both soft and hard woods with the bark left on the edges are frequently damaged by flatheaded and roundheaded wood borers, which hatch from eggs deposited in the bark before or after the lumber is sawed. There are examples of losses from this character of injury amounting to from 20 to 50 per cent or more. Telegraph and telephone poles, posts, mine props, etc., are fre- quently injured before they are set in the ground, especially if the bark remains on them during a few weeks after the middle of March. SEASONED PRODUCTS IN YARDS AND STOREHOUSES. Powder-post heetles. — Hardwood lumber of all kinds, rough handles, wagon stock,, etc., made partially or entirely of sapwood, are often reduced in value from 10 to 90 per cent by a class of insects known as powder-post beetles. The sapwood of hickory, ash, and oak is most liable to attack. Tlie reported losses from this source during the past five or six years indicate that there has been an average reduction in values of from 5 to 10 per cent or more. (Hop- kins, 1903r-, 1905«.) Old hemlock and oak tanbark is often so badly damaged by vari- ous insects which infest dead and dry bark that in some lanyards as much as 50 to 75 per cent of the bark that is over three years old is destroyed. In one tannery in West Virginia it is estimated that more than $30,000 worth of hemlock bark was thus destroyed. (Hop- kins, 1905«.) FINISHED PRODUCTS. The greatest loss of finished hardwood products, such as handle, wagon, carriage, and machinery stock, is caused by powder-post beetles. This is especialh- true of hickory and ash handles and like products in the large and small storehouses of the country, including the vast amount of material held in storage for the army and navy. When material of this kind is once attacked it is usually worthless for the purposes indicated, and therefore must be replaced with new material. In soiye cases losses have amounted to from 10 to 50 per cent, and it is estimated that the average losses have been as much as 10 per cent on nearly all sapwood material that has been in storage more than one year. (Hopkins, 1903e, 1905rt.) UTILIZED PRODUCTS. » Poivder-post heetles, white ants, and other uiood-horing insects. — The finished woodwork in implements, machinery, wagons, furniture, and the inside finish in private and public buildings are often seri- ously damaged by jwwder-post beetles, thus requiring increased de- mands for new material. (Hopkins, 1903«r", 1905a.) INSECT DEPREDATIONS IN NORTH AMERICAN FORESTS. 67 Construction timbers and other woodwork in new and old build- ings are often so seriously damaged by powder-post beetles, white ants, and other wood-boring insects that the affected material has to be removed and replaced by new. or the entire structure torn down and rebuilt. (Hopkins, 11)05«.) Construction timbers in bridges and like structures, railroad ties, telephone and telegraph poles, mine props, fence posts, etc., are sometimes seriously injured by wood-boring larvte, termites, black ants, carpenter bees, and poM'der-post beetles, and sometimes reduced in efficiency from 10 to 100 per cent. INSECTS IX THEIR RELATION TO THE REDUCTION OF FUTURE SUPPLIES OF' TIMBER. Insects not only reduce future supplies by killing the mature- trees and destroying the wood of timber that is inaccessible for utilization, but through injuries inflicted upon trees during the flowering, fruiting, germinating, seedling, and sapling periods of early groAvth they prevent normal reproduction and developments (Hopkins, 190-trt, 1906f.) INTERRELATIONS OF FOREST INSECTS AND FOREST FIRES. Investigations conducted by the writer and assistants in all sec- tions of the country during the past ten years indicate to them quite conclusively that the average percentage of loss of merchant- able timber in the forests of the entire country to be charged tc^ insects during a five or ten year period is infinitely greater than most people realize. (Hopkins, 1906^, pp. 4-5, 1908&, p. 345, 19095, pp. 5, 24 ; Forbes, 1909, pp. 51-52.) Losses from fairest insects. — The writer estimates (p. TO) that for a ten-year period the average amount of timber in the forests of the entire country killed and reduced in value by insects would represent an average loss of $62,500,000 annually.'' It has been estimated (Hopkins, 19055, p. 5; 1908r^ p. 162) that the Black Hills beetle killed approximately 1,000,000,000 feet b. m. of timber during a period of ten years, which at $2.50 per thousand would amount to an average of $250,000 annually. This is merely one example of very destructive depredations by a single species of barkbeetle in a single national forest.'' (See also p. 70.) Prof. Lawrence Bruner, state entomologist of Nebraska, at a meet- ing of the American Association of Economic Entomologists, held at '^Losses from forest fires. — It has been estimated that "on the average, since 1870, forest fires have yearly cost $50,000,000 in timber." (Cleveland, T., jr., 1909, p. 3.) * It has been estimated that the losses of timber from forest fires on all of the National Forests of the Ignited States from 1905 to 1908, inclusive, average- only $165,062 annually. (Cleveland, T., jr., 1908, p. 541.) 12877— Bull. 58, pt 5—09 3 68 SOME INSECTS INJURIOUS TO FORESTS. Baltimore, Md., in December, 1908, spoke as follows : " I can agree with Doctor Hopkins that the insects are far more important in destroying our forests than fires." (Bruner. 1900. p. 53.) Insect-killed timber as fuel for fires.— It has often happened that after insects have killed the timber over extensive areas the standing and fallen dead trees furnished fuel for great forest fires which have not only destroyed or charred the dead timber but killed the living timber and reproduction and swept on into adjacent areas of healthy timber. Indeed, abundant evidence has been found during recent in- vestigations to indicate that some of the vast denuded areas in the Eocky Mountains and other sections of the country are primarily due to widespread devastation by insects, and that subsequent fires de- stroyed the timber and prevented reproduction. (Hopkins, 1906«.) It is also evident that a considerable percentage of dead timber, and especially that found in coniferous forest regions, which has gen- erally been believed to have been fire-killed is a result of primary at- tack by insects. This has been demonstrated in many cases by the pitch-marked galleries of the destructive barkbeetles on the surface of the wood of the old dead trees which had escaped subsequent fires. Fire-Jcillecl timher injured hy insects. — It is true that a vast amount of timber has been killed outright or has died as the direct result of forest fires, but in almost every case observed insects have contributed to a greater or less extent to the death of recently fire-injured trees which might otherwise have recovered, and especially to the rapid deterioration of the wood of a large percentage of the injured and killed trees. It is evident that in some cases fire-scorched and fire- killed timber has contributed to the multiplication of one or more of the insect enemies destructive to living timber, and thus the injury started by the fire may have resulted in a destructive outbreak of beetles. However, it is evident that this has happened only when the destructive beetle was already present in abnormal numbers in the forest surrounding the fire-swept area. Therefore, it is believed that injuries hy fire are not as a rule an important factor in contrib- uting to subsequent depredations hy barkbeetles. Such fires, how- ever, contribute to the multiplication of the insects which depredate on the bark and wood of dying and dead trees, so that in forested areas where fires are frequent the damage to the wood of such trees is more severe, and fewer injured trees recover on account of the abundance of secondary barkbeetle enemies which do not. as a rule, attack and kill living timber. Destruction of insects by ;?ye.— There is another important feature in the relation of insects and fire, in Avhich the fire contributes to the destruction of the principal barkbeetle enemies of the living timber. This happens when the fire burns the timber while it is infested, thus effectually destroying the broods of the insects. It is perfectly plain that the dying and dead foliage of the beetle-infested trees and the INSECT DEPREDATIONS IN NOETH AMERICAN FORESTS. 69 dead bark on the trunks would contribute to the spreading of crown jBres and thus the bark on the entire infested trunks would be suffi- ciently scorched to kill the insects. Therefore, complete fire control maj^ easily contribute to more extended depredations by insects on the living timber, thus increasing, rather than diminishing, the need for insect control. However, the setting of fires or permitting them to burn for the purpose of combating insects should never be under- taken or permitted. Durability of insect-killed thnber. — Some of the matured larch trees which evidently died as a result of defoliation by the larch worm between 1881 and 1885. and which had escaped subsequent depredations by fire and wood-boring insects, were found by the writer in 1908 to be standing and sound enough to be utilized for railroad ties and many other purposes. Under similar conditions the heartwood of red spruce and white pine in the East, of Engelmann spruce in the Rocky Mountains, and of Douglas fir in the Northwest coast region have been found by the writer to be sound enough for j)rofitable utilization for pulp wood, lumber, fuel, and other pur- poses from twenty to thirty years after it had been killed by insects or fire. Thus it is shown that timber killed by insects and fire would be available for utilization for man}^ years were it not for injuries through the secondary attacks of wood-boring insects and the de- struction of insect-killed timber by forest fires. INTERRELATION OF FOREST INSECTS AND FOREST FUNGI. Decay following inji/ry hy insects. — It is well known that the burrows in the bark and wood of living and dead trees and in the crude and finished products often contribute to the entrance of bark and wood decaying fungi. Deterioration and decay are thus far more rapid than would otherwise be possible. It is also known that trees injured and dying from primary attack by parasitic fungi are attractive to certain insects which breed in the bark and wood of sickly and dying trees, and that certain other complicated troubles affecting forest trees are the result of an intimate interrelation and interdependence of insects and fungi. There can be no doubt, how- ever, that certain species and groups of both insects and fungi are independently capable of attacking and killing perfectly vigorous and healthy trees. SUMMARY AND ESTIMATES RELATING TO CHARACTER AND EXTENT OF INSECT DA3IAGE. The killing of trees by insects; the damage by them to the wood of living, dying, and dead timber; the destruction of insect-killed timber by subsequent forest fires; the damage to fire-killed timber by insects; and the damage from decay resulting from insect injuries to the wood, have all been more or less continuous for centuries and are still going on in the forest and woodland areas of this country. 70 SOME INSECTS INJURIOUS TO FORESTS. While these depredations are not always evident or important in all forests or localities, yet almost every year, somewhere in the forests of the country, there are widespread depredations. In every forest and woodland there is an ever present but incon- spicuous army of insects which require the bark, wood, foliage, and seeds of the various tree species for their breeding places or food. Thus, the accumulated but inconspicuous injuries wrought during the period required for the growth of a tree to commercial size go far toward reducing the average annual increment below the point of profitable investments. The accumulated damage to crude, finished, and utilized products reduces the profits of the manufacturer, increases the price of the higher grades to the consumer, and results in an increased drain on the natural resources. In any attempt to estimate in dollars or feet, hoard measure, the extent of losses or Avaste of timber supplies caused by insects there are many conflicting factors which contribute to the difficulty of ar- riving at accurate conclusions. The published information concern- ing the amount in board feet of standing timber in the country is admittedly onh^ an estimate, as are also the published data relating to average stumpage value. The published statistics relating to the amount and value of forest products are of course more accurate, but until more complete data can be furnished by the forest experts on the various complicated phases of forest statistics, any figures given by the forest entomologist relating to the value of timber and com- mercial products destroyed or reduced in value by insects must be considered on the same basis as the other estimates, and as the best that can be presented on available evidence. Standing timber killed and damaged hy insects. — ^^-lien we con- sider the amount of standing merchantable timber killed by insects and the amount of standing timber, living, dying, and dead, which has been reduced in quantity and value through their agency during a ten-year period, we would estimate that such timber represents an equivalent of more than 10 per cent of the quantity and stumpage value of the total stand of merchantable timber in the United States at any given time." A certain percentage of such timber is a total " The estimate of the area and stand of the present forests of the United States, as given in C'ircular 166 of the Forest Service, page 6, is two trillion five hundred billion feet (2,500,000,000.000) board measure. The average stumpage value has been given as .$2.50 per one thousand feet b. m., making a total value of the standing merchantable timber of $6,250,000,000. Ten per cent of this amount would be .$625,000,000, as the amount to be charged to in- sects for a 10-year period, or an avera.ge of .$02.5(t0.000 annually. As an ex- ami)]e. it has been estimated that over l,0(M),OOO.Ono feet b. m. of timber was killed by the Klack Hills beetle in the Black Hills National Forest within a period of ten years. This, at $2.50 per one thousand feet stumpage, would be an average of $250,000 annually in a single forest of 1,294,440 acres. INSECT DEPREDATIONS IN NORTH AMERICAN FORESTS. 71 loss because of the impossibility of utilization; but in some cases a greater or less jDercentage can be, and in some cases is, utilized within the period in which it is of sufficient value to yield a profitable return on the cost of logging and manufacture, although its \a\ue is greatly reduced. Reduction in the Nation's tvealfh. — When we consider the forest resources both in merchantable timber and young growth as an im- portant asset of the Nation's wealth; as representing a given value to the people for direct utilization ; as a cover to the soil for protec- tion of the land from erosion ; as protection of headwater streams and of game; and as contributing to the aesthetic value of health and pleasure resorts, it would be difficult indeed to estimate the amount or percentage of loss of timber or the reduction in the land values, in each case, chargeable to insects. It is plain, however, that in the aggregate it is considerably greater than when estimated on stumpage A'alues alone. Reduction in cash revenue. — When we consider the problem from the standpoint of direct utilization we can estimate the annual loss on a basis of mill values ; but here again we meet with complications, since much of the damaged material is left standing or is discarded in the woods or at the mill without measurement. Therefore we are left to judge from our observations and knowledge of the general conditions as regards dead and damaged timber found in the forests of the country, and the information from lumbermen in different sec- tions, as to the percentage of loss from defective timber. On this basis we can estimate that the amount of insect-killed and damaged timber left in the woods, plus the reduction in value of that utilized, to be charged to insects is not far from an equivalent of 10 per cent of the value of the annual output of forest products of all kinds, in the rough. The total value of the forest products of the United States in 1907 is given as $1,280,000,000; the losses from insect depre- dations would therefore represent an annual loss in a cash value of more than $100,000,000. (Hopkins, 1895c', 1904a.) Reduction in value of fnislied and commercicd iwoducts. — AMien we consider the aggregate loss to the manufacturers of the finished products, to the trade, and to the consumer from insect injuries to the wood, it is evident that it amounts to many millions of dollars in addition to the estimated loss of crude products, or at least 3 per cent of the mill value. METHODS OF PREVENTION AND CONTROL. The results of extensive investigations and of practical applications of the knowledge gained during recent years have demonstrated that some of the most destructive insect enemies of American forests and of the manufactured and utilized products can be controlled, and 72 SOME INSECTS INJURTOUS TO FORESTS. serious damag^e prevented, with little or no ultimate cost over that involved in forest management and business methods. (Hopkins, 1004^;. 1905«, 1908^/, 1909Z>.) There are, of course, certain insects and certain injuries which, under present conditions and available information, can not be con- trolled or prevented, but it is very evident that if the information now available through the publications of the Department of Agri- culture and through direct correspondence Avith its experts is properly- utilized in the future it Avould result in the prevention of at least 30 per cent of the estimated annual waste of forest resources that has been caused by insects within recent years, and thus contribute greatly to the conservation of forest resources. GENEKAL I'KINCIPLES OF CONTROL. .The ordinarj' spraying and similar methods employed in dealing with fruit and shade tree insects are, of course, not available for practical application in the case of forest trees. But there are other and less expensive methods of accomplishing the desired results. In all efforts to control an outbreak or prevent excessive loss from forest insects it should be remembered that as a rule it is useless to attempt the complete extermination of a given insect enemy of a forest tree or forest product. Experience has demonstrated that it is only necessary to reduce and weaken its forces 75 per cent or more. It can not then continue an aggressive attack, but must occupy a defensive position against its own enemies until conditions resulting from avoidable negligence and mismanagement by the ow^ners of the forests and manufacturers of forest products favor its again becom- ing destructive. Forest insects can thus be easily kept under control by good management. The desired control or prevention of loss can often be brought about by the ad()i)ti()n or adjustment of those requisite details in forest management and in lumbering and manufacturing oj^erations, stor- ing, transportation, and utilization of the products which at the least expenditure Avill cause the necessary reduction of the injurious insects and establish unfavorable conditions for their future multipli- cation or continuance of destructive work. It is, lunAcver, of the utmost importance that any adjustment or modification in management or business methods should be based on expert technical knoAvledge or advice relating to the species, habits, life history, and natural enemies of the insects involved and the es- sential features of the methods for their control. This should be supplemented by expert knowledge or advice on the principles of technical and applied forestry in the proper management, care, and utilization of the forest and its resources, and still further supple- mented by practical knowledge and experience relating to local con- INSECT DEPREDATIONS IX NOBTH AMERICAN FORESTS. 73 ditions and facilities favorable and unfavorable for success in prac- tical applications according- to the recommended method or policj' of control. As has been shown, the mature or merchantable timber is the most susceptible to injury or death from the ravages of insects. There- fore, considered from the standpoint of insect control and the pre- vention of one of the greatest items of loss, it is important that such matured timber should be utilized before it begins to deteriorate, or before it reaches the stage of unprofitable growth. For the greatest success in dealing with forest insects, it must be recognized that there are certain features in the habits and seasonal histoiy of each species which ditter to a greater or less extent from those of all other species, even of the same genus ; that there are cer- tain features in the characteristics of the various species of trees which difi'er from those of all other species ; and that as a rule it is the technical knowledge of these peculiar features or characteristics of the trees and their enemies Avhich furnishes the clew to successful methods of control. There are also many peculiar features in the prevailing conditions in different localities, some of them favorable, others unfavorable, for the practical application according to a given method, so that Avhile certain general advice may apply in a broad sense and be available for utilization by the practical man. Avhether owner, manager, or forester, without further advice, it is often necessary to diagnose a given case before specific expert advice can be given as to the exact cause and the most effective method or policy to be adopted, just as a physician must diagnose a case of illness or injury before prescribing the required treatment for his patient. Therefore, in a consideration of the problem as to how far the waste of forest resources caused by insects can be prevented and how far the damaged timber can be utilized, we will attempt to give only general statements based on the results of our observations relating to some of the principal kinds of loss discussed in the first part of this paper, namely, by insects which (1) kill the trees, (2) cause injuries to the wood of living timber. (3) reduce future supplies, and (4) cause injuries to the manufactured products. In addition, w'e will consider the utilization of natural enemies of injurious insects, the utilization of damaged timber, and the present conditions and opportunities for success in the general control of forest insects. CONTROL OF BARKBEETLES WHICH KILL TREES. The barkl)eetles which kill trees attack the bark on the trunk and destroy the life of the tree by extending their burroAvs or galleries in all directions through the inner living bark. The broods of young- grubs or larvae develop within the inner bark, on which they feed. 74 SOME INSECTS INJURIOUS TO FORESTS. 'i^hose of some species develop to the adult stage within the inner bark and are exposed when the bark is removed, while those of other species transform to the adults in the outer corky bark and the larvaj are not exposed when the bark is removed. Some species have two or more generations in a season or annually, while others have but one, and in a few species it requires two years for a single generation to develop. (Hopkins. 1009?;.) The barkbeetles of the genus Dendroctonus represent the most destructive enemies of the principal coniferous tree species of Ameri- can forests, and at the same time are among the easiest of control. The general requisites for success are embodied in the following rules : (a) Give prompt attention to the first evidence of a destructive outbreak, as indicated by an abnormal percentage of yellow or red topped dying trees, and especially when such trees occur in groups of ten or more or cover large areas; {7j) secure authentic determination of the particular species of insect responsible for the trouble; and (c) take i^rompt action toward its control according to specific expert advice, published or otherwise, on the best method for the destruction of the necessary 75 per cent or more of the insects in the infested trees. Some of the methods to be adopted to meet the requirements of various local conditions are as follows : (1) Utilize the infested timber and burn the slabs during the period in which the broods of the destructive beetles are in the imma- ture stages or before the developed broods emerge from the bark ; or (2) Fell the infested trees and remove the bark from the main trunk and burn the bark if necessary;" or (3) Remove the infested bark from the standing tim^ber and burn the bark when necessary ; •* or (4) Immerse the unbarked logs in ponds, lakes, or streams, where the bark will remain soaked long enough to kill the insects; or (5) Remove the unbarked logs or products to a locality where there are no trees liable to attack within a radius of 20 miles or more. Maintaining Control of Barkbeetles. Future trouble of a serious nature from barkbeetles which kill trees can be prevented within a given forest or area of greater or less extent if an insect-control policy is adopted in connection with, or independ- ent of, a fire-control policy b,v which groups of dying trees will receive similar prompt attention as that required for the prevention or control of forest fires. In state and national forests. — In all forest reserves in which there is an organized force of rangers and fire wardens or patrols each ° If the ])roods develop to adults in the outer bark, it must be burned : if they develop in the inner bark and are exposed when the bark is removed, burning is not necessary. As a rule the burning of the tops to destroy the insects Is not necessary. INSECT DEPREDATIONS IN NORTH AMERICAN FORESTS. 75 officer should be furnished with instructions for the location of beetle- infested trees, and with equipment and directions for taking the necessary action whenever the conditions demand or warrant it. In private fo7'ests.—PY\\Q.iQ forests should receive the same atten- tion as public forests, but this is often far more difficult on account of intervening- forests, where the owners either can not or will not give the matter the required attention, "While it may be advisable to have some laws to govern the treatment of timber infested with a dangerous pest, when the owner refuses to take any action such a laAv should apply only to the more extreme cases or as a last resort on authoritative advice, It is probable that in most cases legislation will not be necessary, and more ultimate good will result without than with strict laws, especially when it can be made clear to the owner that his personal interests demand that he take the proper action and that, when necessary, his neighbors will render assistance, as is done in the case of a forest fire. InaccessihJe areas. — There are yet large inaccessible areas in the East and West where it is not practicable or possible at present to con- trol the depredations by these beetles and which must therefore be left to the same natural adjustment that has been going on in all for- ests from their beginning. "\"\'liile under such natural control much of the older matured timber will be lost it will usually be replaced by young growth, either of the same species of trees or of a different species, so that under normal conditions the forest will be perpetu- ated; but under exceptional conditions and combinations of detri- mental influences, such as secondary insect enemies, fire, drought, etc., extensive areas may be completely denuded, never to be reforested under natural conditions. Therefore it will evidently not be very long before it will pay to adopt insect-control policies even in the areas that are inaccessible for profitable liunbering. Examples of Successful Control of P.akkbeetles. We have a sufficient number of examples of successful control of depredations by the destructive barkbeetles to demonstrate the prac- ticability of the advice based on the results of recent entomological investigations. Control of the eastern spruce heetle. — The control of an alarming outbreak of the eastern spruce beetle {Dendroetonus piceaperda Hopk.) in northeastern Maine in 1.000 and 1001 was effected by the concentration of regular logging operations into the areas of infested timber and placing the logs in lakes and streams and driving them to the mills on the Androscoggin River. Thus, with little or no addi- tional expense, there was a saving to one firm, according to its esti- mates, of more than $100,000. 12877— Bull. 58, pt 5—09 4 70 SOME INSECTS INJURIOUS TO FORESTS. Control of the Black Hills beetle.— An extensive outbreak of the IJluck Hills beetle {Dendroctonus j^onderoscB Hopk.) in the vicinity of Colorado Springs, Colo., in 1905-6, which was threatening the living pine timber of the entire section, was brought under control through the eliorts of the private owners of forests and those of for- est officials in the adjoining National Forests. It was accomplished l)y cutting and barking about 1,000 beetle-infested and beetle-killed pine trees. The cost of the operations was largely, if not entirely, covered by the utilized felled timber, although there was consider- nble unnecessary expense involved through the felling and barking of trees from which the beetles had emerged and from the unnec- essary burning of the bark and tops. The successful control of another serious outbreak of the Black Hills beetle, in 1906, on an extensive private estate in southern Colo- rado, was effected through the efforts of the owners, who had some ."^OO infested trees felled and barked within the necessary period to destroy the broods. A large percentage, but not all, of the infested timber was thus treated. These operations were so successful that not a single infested and dying tree could be found when the area was inspected in 1908. In this, as in the other case, considerable unnec- essary expense was involved in the burning of the bark and tops, l)ut the value of utilizable timber was evidently more than enough to pay all expenses. It is evident that in this case a destructive inva- sion was prevented. The most striking example of success relates to a large estate near Idaho Springs, Colo., and in the adjoining Pike National Forest. In May, 1907, it was found that some 63,000 feet of standing timber on the estate was infested by the Black Hills beetle, and the owner was advised by the Bureau of Entomology that unless the ravages were checked at once the beetle would kill the timber not only on this estate but that on the adjoining estates and National Forest, and that therefore radical action should be taken according to the rec- ommendations and detailed instructions given relating to a necessary control policy. No action was taken, however, before the first of the following July, and therefore not in time to prevent the broods of beetles from swarming from the infested trees and extending their ravages. In December, 1907, another examination of the timber was made, and it was found that instead of 65,000 feet of timber in the old infestation there was nearly four times as much timber involved in the new, or over 250,000 feet. The owner was again notified of the serious character of the outbreak, and further suggestion made that if the logs from the infested trees were con- verted into lumber and the slabs burned before May, 1908, it would result in the protection of the remaining living timber. Immediate steps were then taken by the owners to carry out the original INSECT DEPREDATIOKS IN NORTH AMERICAN FORESTS. 77 recommendations. An expert in locating infested timber, workino; under instructions from this Bureau, gnve instructions to the mana- ger of the estate in locating and marking the infested trees and in the essential features in the methods of utilization to destroy the necessary number of beetles; he also marked infested timber on an adjoining estate and on the National Forest. Five months later, in May, 1908, this expert reported that the larger clumps of infested trees on the estate had been converted into lumber and the slabs burned, and that the marked trees on the adjoining estate and National Forest had been cut and barked. In November, 1908, another inspec- tion of the forest on the estate and surrounding area was made by the expert, and on December 1 he reported as follows: Nothing could be more satisfactory than the results obtained by the cutting of the infested timber on the estate. Your recommendations and iustructioTis submitted to the owner, and carefully followed by the manager of the estate. have clearly demonstrated that insect infestation can be controlled, and at no expense to the owner of the timber involved: in fact a very satisfactory price was realized, resulting in a net profit, I understand, of over $5 per thousand feet, board measure, on the 240,000 feet cut. This, of course, does not include the profit of the milling operations, but for the logs sold at the mill, after de- ducting the expenses of cutting and logging. The sawmill was owned and oper- ated by an Idaho Springs firm, and the manufactured ai'ticle sold in that town. I spent six days on the estate, November IS to 23. After a very thorough ex- amination of the timber, I found only three infested trees, isolated individuals, and over a mile from where the large clumps of infested trees were cut. With the exception of those three trees, there is no new infestation on the estate. I also examined the adjoining lands, but no new infestation was observed. The infested trees which I marked in December, 1907. had been cut and barked. On the Pike National Forest, contiguous to the first mentioned estate, where you will remember I marked some clumps of infested trees, no new infestation was found, not one tree. This most gratifying result demonstrated two important things: One, that an extensive outbreak by the most destructive barkbeetle enemy of the pine timber of the central Rocky Mountain forests, in- volving in this case more than 1,000 infested trees, can be controlled without exi^ense, and even at a profit, whenever the conditions are favorable for the utilization of the infested timber; the other, that the essential details of the recommendations and expert advice, based on the results of scientific research, can be successfully applied by a manager of a private forest or by the rangers of national and state forests. It also indicates quite conclusively that the widespread dep- redations in the Black Hills National Forest could have been prevented with very little expense to the Government if the matter had received prompt attention in 1901, when the first investigations were made and essentially the same recommendations submitted. But. through the lack of public appreciation of the importance of the problem at the time, and the lack of sufficient authority and funds later, the out- break was allowed to extend beyond practical control, and in conse- 78 SOME INSECTS INJURIOUS TO FORESTS. (Itience :i larce percentaire of the timber of the entire National Forest has been killed. There were, then, no forcible examples of the prac- tical value of such recommendations based on scientific research, and no other argument was effective in arousing public interest in the threatening character of the outbreak or confidence in scientific ad- vice or methods of control. Now we have several examples demon- strating the practicability of forest-insect control in America which should lead to confidence in the results of scientific research as a basis for success in practical application. Control of the hickory harkljeetle. — The complete control of the hickory barkbeetle (Sroh/tiis quadrispinosus Say), which threat- ened the total destruction of the hickory trees on Belle Isle Park, at Detroit. Mich., in 1903. was effected by felling and removing the infested trees and converting them into merchantable products, all without cost to the park commission. (Hopkins, 19045.) CONTROL or INSECTS WHICH CAUSE DEFECTS IN LIVING TIMBER. The class of insects which causes defects in the wood of living timber can be controlled to a greater or less extent, depending upon local conditions, and a large percentage of the losses prevented through the adoption of certain requisite details in forest manage- ment. Of the.-e the following are especially important : (1) The utilization of all of the defective and infested timber that will pay expenses for manufacture into merchantable products, such as lumber, cordAvood, etc. (2) The burning of infested timber and w^aste material not avail- able for use. including dead standing and fallen timber, to remove the breeding places of insects like the oak timber worm and the chestnut timber worm, which go from the dead to the living timber. (?)) The prevention of wounds of anj^ kind in the bark of living trees. (4) The prevention of future losses by the practice of improved forestry methods which will eliminate favorable conditions for injury and contribute to a perpetual supply of vigorous, healthy timber to be utilized before it passes the stage of profitable increment. PREVENTION OF INJURY TO DYING AND DEAD TREES. A large percentage of the injury to the wood of insect, fire, and lightning killed trees and those killed or dying from injuries by storms, disease, etc., can be prevented as follows : (1) By the prompt utilization of such timber Avithin a few w^eeks or months after it is dead or found to be past recovery. (2) By removing the bark from the merchantable portions of the trunks within a fcAv weeks after the trees are dead (the work to be done either before or after the trees are felled). INSECT DEPEEDATIONS IN NORTH AMERICAN FORESTS. 79 (3) By felling the trees and placing the unbarked logs in water. (4) By the adoption of a system of forest management which will provide for the prompt utilization of all trees which die from any cause. PREVENTION OF LOSS FROM INSECT INJURIES TO NATURAL AND ARTIFICIAL REPRODUCTION. The successful control of the insects which destroy or prevent the normal development of natural reproduction is a far more difficult problem than that presented by other classes of insect injuries, but in this as in the others a great deal can be accomplished toward pre- venting the reduction of future supplies. Much can be accomplished in nurseries and small plantations by the adoption of the ordinary methods of controlling farm and or- chard insects, but in the natural forests reliance must be placed largely on systems of forest management which will bring about unfavorable conditions for the work of the more important enemies. (Hopkins, 1906c.) Utilization of Immune and Resistant Varieties and Races of Trees. Certain individuals representing varietal or racial forms of trees of a given species are sometimes found to be either immune or de- cidedly more resistant to the insects which are destructive or seri- ously injurious to the life or wood of other individuals or varieties of the same species. This fact suggests the importance of recogniz- ing the well-known principle of improvement by selection. Thus, selecting seed or cuttings from such immune and resistant trees for artificial propagation, or taking great pains to leave such trees in commercial or selection cuttings for natural reproduction, will un- doubtedly be an important step toward providing against damage and loss in the future. (Hopkins, 19066, IdOla, 1907c, ld07d.) PREVENTION OF INSECT IN.Jl RIES TO FOREST PRODUCTS. The problem of artificial control and prevention of insect injuries to forest products offers less difficulties perhaps than that relating to many other branches of the general subject of forest-insect con- trol. In most cases the principle of prevention is the only one to be considered, since the damage is done soon after the insects enter the wood, and therefore it can not be repaired by destroying the enemy. Crude Products. The proper degree of moisture found in the bark and wood of newly felled trees, saw logs, telegraph poles, posts, and like material, cut in the fall and winter and left on the ground or in close piles 80 SOME INSECTS INJURIOUS TO FORESTS. during a few Aveeks or months in the spring and summer, or during the period when the particular species of injurious insects are flying, are some of the conditions most favorable to attack. The period of danger varies with the kind of timber and the time of the year it is felled. Those felled in late fall and winter will generally remain attractive to ambrosia beetles and adults of round and flat headed borers during March. April, and ]May. Those felled during the pe- riod between April and September may be attacked in a few days after they are felled, but the period of danger from a given species of insect may not extend over more than a few weeks. Thus cer- tain kinds of trees felled during certain seasons are never attacked, while if they are felled at other times and seasons the conditions for attack may be most favorable when the insects are active, and then the wood will be thickly infested and ruined. The presence of bark is absolutely necessary for successful infestation by most of the wood- boring grubs, because the eggs and young stages must occupy the in- ner and outer portions before the latter can enter the wood. Some ambrosia beetles and timber worms will, however, attack barked logs, especially those in close piles or otherwise shaded or protected from rapid drying. A large percentage of the injury to this class of products can be prevented, as follows : (1) Provide for as little delay as possible between the felling of the tree and its manufacture into rough products. This is especiallj^ necessary with trees felled from April to September in the region north of the Gulf States and from March to November in the latter, while the late fall and winter cuttings should all be worked up by March or April. (2) Do not leave the round timbers in the woods or on the skid- ways during the danger period, or, if this is unavoidable, take every jDrecaution to facilitate the rapid drying of the inner bark by keeping the logs off the ground, in the sun, or in loose piles, or else, if possible, the opposite extreme should be adopted and the logs kept in water. (3) Remove the bark within a few days after the trees are felled, from poles, posts, and other material which will not be injured by checking or season cracks. (4) Take advantage of the proper months or seasons in which to fell or girdle different kinds of trees to avoid danger. Damage to products cut from saplings and left with the bark on can be prewnted by transporting the material from the woods soon after it is cut, so that it will not be left in piles or bundles in or near the forest during the season of insect activity. Damage may also be prevented by care not to leave the material stored in one place for several months. Pinhole damage to stave and shingle bolts cut during a warm season can be prevented by removing the bark from the timber as INSECT DEPREDATIONS IN NORTH AMERICAN FORESTS. 81 soon as it is felled and by converting the bolts into the smallest prac- ticable dimensions and piling them in such a manner as to facilitate rapid drying. Damage to unseasoned handle and wagon stock in the rough can be prevented by taking special precautions to provide against the same favorable conditions for attack as mentioned in connection with round timbers. This is especially necessary Avith hickory and ash if cut during the winter and spring. Damage to pulpwood and cordwood can be prevented to a great extent by placing the sticks of wood in triangular or crib piles im- mediately after they are cut from the trees, especially if the timber is cut during the danger period or must be held for a few months during the warm season. Peeling or splitting the wood, or both, be- fore it is piled will also provide against damage from insects. Manufactured Products. unseasoned products. Freshly sawed hardwood lumber placed in close piles during warm, damp weather in the period from July to September, inclusive, pre- sents the most favorable conditions for injury by ambrosia beetles. In all cases it is the moist condition and retarded drying of the lum- ber which induces attack. Therefore any method which will provide for the rapid drying of the lumber before or after piling will tend to prevent loss. It is important, also, that heavy lumber should, as far as possible, be cut onh^ in the winter and piled so that it will be well dried out before the middle of INIarch. The damage to lumber and square timber when the bark is left on the edges or sides can be prevented by removing the bark before or immediately after the lumber is sawed, or by sawing and piling the material during the winter, or if sawed at other times it should be piled so that rapid drying will be facilitated. SEASONED PRODUCTS. Unfinished seasoned produrfM. — Injury by powder-post beetles to dry hardwood lumber and other material in stacks or storehouses can be i^revented as follows: (1) Have a general inspection of the material in the yards and storehouses at least once a year, preferably during November or February, for the purpose of («) sorting out and destroying or other- wise disposing of any material that shows the slightest evidence of injury, as indicated by the presence of fine powdery boring dust, and (7j) sorting out and destroying all old and useless sapwood material of any kind that will offer favorable breeding places for the insects. 82 SOME INSECTS INJURIOUS TO FORESTS. (2) Prevent the introduction into the lumber yards or store- houses of any infested material, remembering that the insect may be thus distributed to or from all parts of the world. (3) Adopt a system of classification of all dry or seasoned hard- wood stock which Avill provide for (a) the separation of the pure heartwood material from the pure and part sapwood material; (b) classification of all kinds of wood most liable to attack, such as hick- or}', ash, oak; (c) the successive utilization or sale of the older ma- terial (remembering that material one year old or over is far more liable to injury) ; (d) i^roviding against the accumulation of refuse material in which the insects could breed; and (e) treating the best material with linseed oil or kerosene to prevent attack. Finished seasoned jjroducts.—Dainage to finished handles, oars, spokes, rims, hubs, wheels, and other unpainted wagon, carriage, machinery, and implement stock in factories, wholesale and retail storehouses, and army and navy stores can be prevented by the adop- tion of the same general rules as those given under rough products. In addition, damage can be controlled and prevented in the following manner : Sort out and (a) destroy all articles showing the slightest evidence of powder-post injury, or (h) treat with kerosene oil such infested and slightl}'^ injured articles as may be tested for required strength and found to be of sufficient value for retention, placing the same in quarantine for a sufficient time to determine whether the treat- ment is successful. Damage by powder-post insects to many kinds of articles can be pre- vented and at the same time the material otherwise benefited by treat- ing the sapwood with linseed oil or kerosene, either by immersing it in the oil or by applying the oil with a brush, the application to be made as soon as possible after the articles are finished from recently sea- soned, uninjured stock. Past and Present Conditions of Powder-Post Injury. Up to 1906 there were a great many reports of extensive losses of valuable material from the ravages of powder-post beetles which were seriouslj^ aifecting all industries involved in the manufacture, sale, and utilization of the classes of hardwood products affected by them. In response to these reports and accompanying appeals to the Department of Agriculture for information on causes and remedies, the problem was thoroughly investigated and specific advice and in- structions relating to practical methods of control and prevention have been widely disseminated, both through publications of the Department and special correspondence. Reports of present conditions from our principal correspondents, together with the less frequent requests for advice, indicate that INSECT DEPREDATIONS IN NORTH AMERICAN FORESTS. 83 the disseminated information has been extensively utilized and that it has been worth many millions of dollars toward eliminating the losses and reducing the drain on the limited supply of the kinds of timber required to replenish the damaged and destroyed material. The army and navy stores of handles, tent poles, wheelbarrows, oars, and many other hardwood articles have suffered severely from powder-post damage, involving an enormous loss, but the carrying out of the information already supplied has evidently contributed greatly toward the elimination of this source of loss to the Gov- ernment. Tan Bark. Damage to hemlock and oak tan bark by the class of insects which in some cases has been so destructive to these products in the past can be easily prevented without cost, as follows: (1) Utilize the bark within three years from the time it is taken from the trees. (2) Prevent the accumulation in the yards and store-sheds of old bark and waste material in which the insects can breed. These simple methods have been extensively adopted since their recommendation in correspondence and publications between about 1894 and 1904, and afford one of the most striking examples of the value of expert information on the peculiar habits of insects and of how millions of dollars can be saved without cost through a simple adjustment in methods of utilization. Utilized Prodxtcts. Damage and loss from insect injuries to timber and other woodwork in structures of various kinds, to telephone and telegraph poles, posts, railroad ties, mine props, etc., can be prevented to a large extent through the adoption of the proper methods of management or of treating the material with preservatives before and after it is utilized. TIMBERS AND WOODWORK IN STRtTCTURES. Injuries to timbers and woodwork in dwellings, outbuildings, bridges, etc., by powder- post insects can be prevented as follows : (1) Use nothing but heartwood for the concealed parts most liable to damage. (2) If it is necessary to use all or part sap wood material, attack can be prevented by treating the sap portions with kerosene, coal tar, creosote, or linseed oil. Facilities for future treatment can be pro- vided wherever the rough or finished woodwork is exposed, as in outbuildings, bridges, etc., if care is taken to expose the sapwood portions. 84 SOME INSECTS INJUKIOUS TO FORESTS. (3) If the untreated timbers and woodwork in old buildings show evidence of attack, the affected portions should be given a liberal application of kerosene. Damage b}^ white ants, or termites, can often be prevented in the folloAving ways: (1) By the use of nothing but sound wood for underpinning and foundation timbers and the removal of deca3dng timbers from old structures. (2) By preventing moist conditions of the wood in any part of the structure and especially that in foundation timbers. (3) By the treatment of timbers necessarily exposed to moist con- ditions with creosote, zinc chlorid, corrosive sublimate, etc. (4) If the timbers become infested, further progTess of insect dam- age can be prevented by removing the badly damaged parts and soak- ing the remainder with kerosene, fumigating with bisulphid of carbon, and by removing any adjacent decaying or other wood in which the insects have been breeding or may breed, such as logs, stumps, etc. Log cabins and rustic work. — Damage by bark and wood boring insects to the unbarked logs and poles used in rustic cabins, summer houses, fences, etc., can be largely prevented by cutting the material in October and November and utilizing it at once, or by piling it off" the ground or under cover in such a manner as to offer the best facil- ities for the rapid and thorough drying of the inner bark before the middle of March or the 1st of April following. If these necessary precautions are not taken, and there is evidence that insects are at work in the bark and wood, the damage can be checked by injecting bisulphid of carbon through natural or artificial openings in the affected bark, and immediately stopping these and other openings with putty or a similar substance. Poles, posts, piles, ties, mine props, and similar products. — Insect damage to poles, posts, and similar products can be prevented to a greater or less extent by the preservative treatments which have been tested and recommended by the Forest Service for the prevention of decay. These should be applied before the material is utilized for the purposes intended, or, if it be attacked after it has been utilized, further damage can be checked to a certain extent by the use of the same substances. It is often of prime importance to prevent injury from wood-boring insects, for the reason that such injuries contribute to more rapid decay. Therefore anything that will prevent insect injury, either before or after the utilization of such products, will contribute to the prevention of premature deterioration and decay. INSECT DEPREDATIONS IN NORTH AMERICAN FORESTS. 85 UTILIZATION OF NATURAL ENEMIES AND FACTORS IN THE CONTROL OF INJURIOUS INSECTS. Were it not for the natural checks and natural factors of control of some of the more destructive insect enemies of forest trees and forest products, artificial control would in many cases be impossible, and the depredations would evidently be far more continuous and complete. These natural factors in the control of the depredating insects consist of parasitic and predatory insects, diseases of insects, birds, adverse climatic conditions, etc. A\liile one or more of these beneficial factors exert a continuous and powerful influence toward the prevention of a more extensive waste of forest resources, it has been repeatedly demonstrated that they can not be depended on to prevent widespread devastations or to otherwise work for the best interests of the private or public owner by protecting the best trees and the best tree species. The insects and birds which prey upon the depredating insects also have factors to contend against, consisting of insects, birds, diseases, and climatic conditions. Therefore under normal conditions the tendency is toward the preservation of a bal- ance between the warring factors, but frequently the enemies of the trees get the ascendancy and take on the character of an invasion, which may continue for two or three or even ten years before the bal- ance is again adjusted through the influence of the natural enemies or diminished food supply. Thus a vast amount of timber or of a given forest product may be destroyed before the factors of natural control can prevail. It is evident that the most effective utilization of the factors of natural control will be through the alliance with them of the owner of the forest in the artificial reduction of the enemies of the trees rather than by efforts to make the natural enemies of the injurious insects his allies through artificial introduction or dissemination. The former is accomplished by the adoption of methods of combating the invaders which will reduce and weaken their forces below their power of prosecuting aggressive movements and attacks, or, as pre- viously stated, to reduce their numbers to the point where they must occupy a defensive position against their natural enemies and be dependent for their supplies of food and breeding places upon that furnished through avoidable mismanagement of the forests and manu- facturing operations. Thus the owner of the forest can contribute greatly toward the preservation of a balance which will be to his material benefit. On the other hand, he may in the future, as in the past, contribute greatly to the multiplication of the depredating insects and to greatly increased losses caused by them, through neglect or a disregard of available information on the fundamental prin- 86 SOME INSECTS INJURIOUS TO FORESTS. ciples of insect control in the management of forests and manufac- turing enterprises. Beneficial Insects. The beneficial insects comprise those which are internal or external parasites of the immature or mature stages of the injurious insects, and predators which feed on the young or adults of insects either before or after they make their attack on the trees or products. These two beneficial factors are doubtless far more effective in the long run than any other agencies of natural control. Yet they, in combination with all other factors, can not be always relied upon to render con- tinued and efficient control. They can, however, be relied upon to respond to artificial assistance in reducing the numbers of the depre- dators. Beneficial Diseases of Insects. It is very evident that the parasitic fungi and bacteria which some- times cause epidemics among injurious insects often exert la powerful influence toward the control of extensive outbreaks or invasions of insect enemies of forests. Indeed, it appears that the greatest serv- ice rendered by this class of natural enemies is in the frequent sud- den appearance of an epidemic which kills off a destructive species of insect after the latter has increased to such numbers and extended its depredations over such vast areas as to be far beyond the control of man or his insect and bird allies. Numerous examples of this kind of natural control are found in the sudden ending of widespread depredations by various species of caterpillars and sawfly larva3 which defoliate deciduous and coniferous trees. As a rule, however, the beneficial effects of the diseases of insects prevail only after the injurious insects have increased to excessive numbers. Therefore this factor of insect control can not be depended upon to hold the insects in check or prevent outbreaks. The fact, however, that it operates on a class of insect enemies of the forest (defoliators) which at present can not be controlled by any known artificial methods renders the serv- ices of the diseases all the more valuable. It is believed that with further knowledge of nature's method of propagating, perpetuating, and disseminating the diseases which cause epidemics among insects, they may be utilized more or less successfully through artificial propagation and dissemination to prevent threatened invasions of defoliating insects. Beneficial Birds. It is very evident that certain kinds of birds, such as woodpeckers, render valuable service toward the natural control of destructive bark and wood boring insects. They appear to render the greatest INSECT DEPREDATIONS IN NORTH AMERICAN FORESTS. 87 service, however, where but few trees are being killed or injured, because their concentrated work on such trees may contribute toward the prevention of an abnormal increase of the insects. They also render some service as allies of the other beneficial factors which assist in artificial control. It is evident, however, that where many hun- dreds or thousands of trees are being killed the comparatively lim- ited number of birds in any forest under the most favorable condi- tions could have little or no beneficial effect. Therefore, while the birds should be classed among the valuable friends of the forest, and should be protected, it is plain that they can not, even with the utmost protection, always be relied upon to protect the forest against destruc- tive ravages of insects. We must remember, in this connection, that there are complicated interrelations between birds, injurious insects, and beneficial insects which do not necessarily always operate to the benefit of the forest. In fact, it may sometimes be quite the reverse. Therefore, in order to derive the greatest benefit from the conflict between the birds, the insect enemies of the trees, and the insect friends of the trees, we must utilize our knowledge of the factors which are contributing toward the preservation of a balance, so that whenever the enemies of the forest threaten to get beyond natural control we may enter the field through artificial means and endeavor to force them back to their normal defensive position. Beneficial Climatic Conditions. The benefits to be derived from climatic conditions which are det- rimental or destructive to insect enemies of the forest, while some- times very great, are necessarily unreliable, and thus can not be depended upon to assist in artificial control. In fact, the very con- dition which may contribute to the destruction of one depredator may favor the multiplication of another. UTILIZATION OF WASTE CAUSED BY INSECTS. When we come to consider the vast amount of standing timber in the forests of the country which has been injured or killed by insects, and will go to waste if it is not utilized within a limited period, we realize that there are great possibilities in its utilization as a means of preventing the reduction of future supplies of living healthy tim- ber. It is all the more important that the insect-infested timber should be utilized, because in so doing we can contribute more per- haps than in any other way to the reduction of the insects to or below their normal numbers, and thus provide against serious injury in the future, as well as to the maintenance of control. 88 SOME INSECTS INJURIOUS TO FORESTS. PRESENT CONDITIONS AND OPPORTUNITIES. Unfortunately, the examples of management, or rather misman- agement, which are contributing to an extension or increase of waste are far in excess of those which under proper management are con- tributing to the reverse. This is due in a large part to the conditions that have prevailed in American forests in the past that have ren- dered it impracticable to adopt improved policies of forest manage- ment, but at present it is largely due to a lack of appreciation of the importance of the subject, and of the opportunities to prevent such losses, when it is not only practicable but possible to do so, and when it will, at the same time, yield large returns on the necessary addi- tional expense. This is especially true in thousands of farmers' wood- lots and private holdings in the States east of the Mississippi River, in which from 25 to 90 per cent of all of the serious injury of the past can be prevented in the future with little or no additional ex- pense over that required for ordinary good forest management. Forest Entomology as Applied to American Forests. It is only within the past eleven years that any attempt has been made toward a systematic investigation of the insect enemies of the forest trees and forest products of the entire country. The state of knowledge of the subject previous to that time can be judged by the fact that a number of the most destructive enemies of forest trees are found to be new to science, and that nothing whatever was known of the habits and seasonal history of a large number of the more im- portant known species which are common enemies of forest trees and forest products, while scarcely anything was known in regard to practical methods of controlling the principal enemies of the forest and its products, or of preventing losses from their ravages as applied to conditions in this country. present knowledge. Within the past ten years forest-insect investigations have been con- ducted by the Bureau of Entomology of the Department of Agricul- ture in all of the principal forest regions of the United States, and have led to the following results: Results of investigations. — Satisfactory progress has been made toward the attainment of some of the fundamental objects of the in- vestigations, one of which has been the laying of a substantial founda- tion for forest entomology in this country on which future progress can be made along the lines of acquiring, disseminating, and applying information of immediate practical value in the protection of our forest resources. Acquired and new information. — ^The principal insect enemies of the forests and forest products of North America have become INSECT DEPREDATIONS IN NORTH AMERICAN FORESTS. 89 known, and the general character and extent of their depredations have been ascertained. The more important facts in the life history, habits, and practical methods of control relating to some of the more destructive insects have been determined. A mass of original data has been collected relating to forest in- sects in general, including not only those which are destructive or injurious, but also those which are beneficial or neutral in their rela- tion to the forest, as represented by a collection of more than a mil- lion specimens of insects and their work. As a direct result of the investigations of forest insects during the past six years, at a cost of less than $53,000, there has been accumu- lated a reserve fund of information now available through publica- tions, correspondence, and field demonstrations which, if properly utilized for practical application, would evidently prevent from 10 to 30 per cent of the annual losses at a very small cost. Disseminated information. — In addition to information dissemi- nated in all sections of the country through correspondence, lectures, demonstrations, exhibitions, etc., the published information, based on results of investigations conducted by the West Virginia Agri- cultural Experiment Station and by the Bureau of Entomology of the U. S. Department of Agriculture during the past eighteen j^ears, is represented by over 1,300 pages, 99 plates, and 340 figures. (See list of publications.) NEEDS. The work that has been done is only a beginning in the vast field of forest entomology. There is need of more systematic work (or so-called pure science) on the different stages of the thousands of species of injurious and beneficial insects involved. This is abso- lutely necessary in order to have the further scientific basis of facts on which to build the structure of complex details necessary to suc- cess in practical application in its broadest sense. There is need of further detailed study of habits and seasonal his- tory of the species of injurious and beneficial insects, as well as of the local and other conditions favorable and unfavorable for their mul- tiplication and work. Further information is desirable on the principal factors of nat- ural control of injurious insects, in order that it may be better util- ized to facilitate artificial control. There is special need of more general information and public in- terest in the subject of losses from insect depredations on standing timber and timber products, and a better realization of the possibility and practicability of preventing losses. Looking to this end, there is need of further demonstration and educational work along the lines which will bring the matter to the 90 SOME INSECTS INJURIOUS TO FORESTS. attention of the man in the woods, sawmill, factory, or trade who is in direct touch with the local conditions and business methods. There is a special need of more experts in forest entomology, and there will be an increasing demand for such experts in the future, to organize and take charge of insect-control policies in state forests, in public parks, in the more extensive private or commercial forests, and in extensive manufacturing enterprises, and to give instructions to students in forestry schools and forestry departments in state and other institutions of learning. The need of trained and experienced experts in forest entomology for all of this class of work can not be too strongly urged. There is perhaps no branch of economic or applied science which requires more technical knowledge and practical experience as a basis for proper investigations and authentic instructions and atlvice than forest entomology, and there is perhaps no other feature in the science and practice of forestry in which advice and application based on insufficient knowledge is so dangerous. There is quite a general recognition of the importance of guarding against contagious diseases, of the necessity of consulting a physi- cian in cases of serious illness, and of rehdng on authorized phar- macists to fill the prescription, and then administering the prescribed treatment according to directions, but it is a notable fact that there are comparativelj^ few persons who, even when deeply interested in preserving the health of the forest, have heretofore recognized the importance of guarding against insect epidemics or of consulting an expert forest entomologist in case of a threatened or existing out- break. It has often happened that when such advice has been sought and received, the treatment was not administered according to the recommendations but changed to suit the ideas of some one entirely ignorant of the facts and principles upon which it was based. This has often resulted not only in failure to accomplish the desired end, but has contributed to an aggravation of the trouble and increased loss. The determination of the cause of specific troubles affecting the individuals of a given species of forest tree or an injury to a given type of product is just as complicated and requires the same elements of experience, training, and skill as that required for the determina- tion of the cause of a given disease or the character of a given in- jury affecting man. It is just as important to know the cause or character of injury in the former as it is in the latter, in order to prescribe the specific treatment which will yield the desired results. Therefore, in order to make the best progress toward preventing future waste of our forest resources from depredations bj^ insects, every one interested in the subject, and especially those in authority in the public and private institutions of investigation and learning, should see to it that the instructions to students and the information INSECT DEPEEDATIONS IN NOKTH AMERICAN FORESTS. 91 given out to the public is not only the best available but that it is limited to the range of expert knowledge of the subject possessed by the instructor or investigator. Elementary and Technical Knowledge of Forest Entomology for the Forester. AVliile it may be desirable that every professional forester should have an expert knowledge of forest entomology, it is rarely possible, even under exceptionally favorable conditions, for him to acquire more than the necessary elementary knowledge, and even this has not been possible under the conditions which have necessarily prevailed in the forest schools, and in the practice of forestry, in this country. Little or no time has been available for acquiring the necessary in- formation from subsequent study and jjractical experience. There- fore this feature in the education of the American forester has been practically neglected. present requirements of instruction. As long as expert forest entomologists and authentic text-books based on American insects and conditions are not available for giving: a complete course in technical and applied forest entomology the requirements of such a course should be limited to instruction in ele- mentary entomology, and in elementary principles of applied forest entomology, which will give the necessary foundation for intelligent observations and utilization of available information as required in future practice. CONCLUSION. There is conclusive evidence that insects have been in the past, and are now, important factors in the waste and reduction of timber supplies, and will continue to be such in the future (pp. 57-58). They attack perfectly healthy trees of all ages and kill thenr (p. 58). They have at times killed a large percentage of the best timber over thousands of square miles of heavily forested lands (pp. 58-60). They reduce the value of living timber and that of crude and finished products (pp. 60-66). The accumulated evidence through many years of investigation and observation in the principal forest areas of the entire country by the writer and the field assistants in forest insect investigations furnishes the basis for the following summarized statements and estimates: A large percentage of pine and spruce timber was killed by the southern pine beetle in 1890-1892 over an area of 75.000 square miles in West Virginia, Maryland, Pennsylvania, Virginia, and North Carolina (p. 58). 92 SOME INSECTS INJURIOUS TO FORESTS. Billions of feet of matured spruce have been killed by the eastern spruce beetle during the past half centuiy in the northeastern United States and southeastern Canada (p. 58). A large percentage of the matured Engelmann spruce of the Rocky Mountains region has been killed by the Engelmann spruce beetle within the past fifty years (p. 59). A large percentage of the pine timber of merchantable size in the Black Hills National Forest and other national and private forests of the central Rocky Mountains region has been killed during the past ten years by the Black Hills beetle (p. 59). A large percentage of the best matured pine timber of the region north and west of Colorado and Utah has been killed within the past twenty years by the mountain pine beetle and the western pine beetle (p. 59).^ A large percentage of the matured Douglas fir, or red fir, of the Rockv Mountains region has been killed by the Douglas fir beetle (p. 59). The supply of hickory timber in the forests and woodlots of the States east of the Mississippi River has been greatly reduced by the ravages of the hickory barkbeetle (p. 60). Practically all of the matured eastern larch has been killed over vast areas in the northeastern United States and southeastern Canada by the larch worm and eastern larch beetle (p. 60). The wood of living timber has been rendered defective by wood- boring insects to such an extent as to reduce the value of a vast amount of standing timber from 50 to 75 per cent (p. 60). Rapid deterioration of the wood of dying and dead trees has been caused by wood-boring insects, often amounting to from 25 to 100 per cent during the period in which it would otherwise be available for utilization (p. 62). Crude manufactured and finished forest products have been dam- aged by insects to such an extent as to cause an estimated average annual loss of 10 per cent of its mill value (pp. 64-67). Insects are the cause of greatly reducing our forest resources by killing the inaccessible timber; by reducing the quantity through injuries to the wood of living and dying timber; by preventing nor- mal reproduction and development of future supplies, and through destroying forest products. GENERAL ESTIMATES OF AMOUNT OF DAMAGE CAUSED BY FOREST INSECTS. The results of extensive observations during the past ten years in the principal forested areas of all sections of the country, and during an additional eight years in West Virginia, indicate to the writer that the amount of standing timber killed by insects, together with INSECT DEPREDATIONS IN NORTH AMERICAN FORESTS. 93 the standing living, dying, and dead timber reduced in quality and value by them in the forests of the country, to be found at any given time, has been not far from 10 per cent of the total stand of mer- chantable-sized timber (pp. 70-71). Considering the forest in its broadest sense as a source of national wealth of a given value for all purposes, including direct utilization, protection of land from erosion, protection of headwater streams, protection of game, and as contributing to the real and aesthetic value of health and pleasure resorts, it is evident to the writer that the total damage caused by insects has been equivalent to an average addi- tional 5 per cent of the value of the merchantable-sized timber of the entire country (p. 71). Considering the problem of insect damage to standing timber and crude products on the basis of direct utilization of the forest re- sources, it is evident that the reduction in value below that of healthy timber or sound products at the time of utilization, including losses from handling defective material, has amounted to an equivalent of at least 10 per cent of the average annual mill value of the aggre- gate output of forest products of all kinds. This, of course, includes the killed and damaged merchantable-sized timber considered under the estimate relating to standing timber, given above. Since the killed and damaged standing timber is involved in any given annual output, this estimate on a basis of utilization represents more nearly a direct reduction in cash values ( p. 71 ) . The writer estimates that the annual loss caused by insects injuri- ous to finished and utilized products, including the consequent in- creased drain on the forest resources to replace that prematurely de- stroyed by insects, is equivalent to at least 3 per cent of the original or mill value. HOW LOSSES CAN BE PREVENTED. The results of extensive investigations and of practical applications during recent years have demonstrated that some of the most de- structive insect enemies of American forests and of manufactured and utilized products can be controlled and serious damage prevented with little or no ultimate cost over that involved in good forest man- agement and business methods. It is evident that if the information now available through publica- tions of the Department of Agriculture and through direct cor- respondence with its experts is properly utilized in the future it will result in the prevention of an equivalent of at least 30 per cent of the estimated annual waste of forest resources that has been caused by insects within recent years and thus contribute greatly to the conservation of the forest resources. This can be accomplished as follows : 94 SOME INSECTS INJURIOUS TO FORESTS. (1) B}^ the adoption or adjustment of certain requisite details in forest management, in lumbering and manufacturing operations, and in storing, transporting, and utilizing the products which, at the least expense, will bring about the necessary reduction of the injurious insect and unfavorable conditions for their future multiplication or destructive work. (2) By the adoption of policies of control, based upon expert tech- nical knowledge or advice relating to the species, habits, life history, and natural enemies of the insects involved, and methods for their control, supplemented by expert knowledge or advice on the prin- ciples of technical and applied forestry in the proper management, care, and utilization of the forest and its resources and still further supplemented b}" practical knowledge and experience relating to local conditions and facilities favorable and unfavorable for suc- cessful application according to a given method or policy of control. (3) By reliance on technical advice furnished b}' recognized ex- perts in forest entomology and forestry as a basis for success in prac- tical application by the owner or forester. (4) By utilization of so-called matured timber, and especially dense or pure stands of such timber, thus removing one of the favor- able conditions for rapid deterioration through attacks by wood- boring insects or death through the attack of destructive bark-boring or defoliating insects. (5) By the utilization of a knowledge of the principles of natural control as a means of contributing to the efficiency of artificial control. (6) By prompt recognition of the first evidences of the work or destructive outbreaks of the principal insect depredators, by authentic identification of the species involved, and by prompt action in adopt- ing the proper method or methods of control for the prevention of losses. It should be remembered that as a rule it is useless to attempt the extermination of an insect enemy of the forest or its products. It is only necessary to reduce and weaken its forces at least 75 per cent, so that it can not continue an aggressive invasion, but must occupj' a defensive position against its own enemies and become dependent upon favorable conditions resulting from avoidable negligence and mismanagement by the owners of the forests and the manufacturers of forest products. While beneficial insects, beneficial birds, and beneficial diseases exert a continuous and powerful influence toward the prevention of a more extensive waste of forest resources, it has been repeatedly demon- strated that they can not be depended upon alwaj^s to prevent wide- spread devastations or otherwise to work for the best interests of the private or public owner by protecting the best trees and the best tree species. INSECT DEPREDATIONS IN NORTH AMERICAN FORESTS. 95 The best way to utilize the factors of natural control is to become their allies and assist in the reduction of the enemy, rather than to try to make them our allies through artificial introduction or dissem- ination. A large percentage of the waste caused by insects can be prevented by the utilization of infested material, and at the same time, without additional expense, this will contribute greatly to the control of insects which cause such waste and also prevent injuries and depredations in the future. Under past conditions the poor management or neglect of the average forest has contributed to the increase of depredations by insects. Under present conditions of better management of local forests and of the more progressive manufacturing enterprises much is being accomplished toward the reduction of losses. In the average forest, and in the average business enterprise dealing with forest products, present conditions are little better than in the past. This is largely clue to a lack of appreciation of the importance of the sub- ject and failure to realize the opportunity and practicability of pre- venting a large percentage of the loss. PUBLICATIONS RELATING TO FOREST INSECTS. HISTORICAL AND GENERAL. 1831. Wilson, Alexander, and Charles Lucien Bonaparte. — ^American Orni- thology. (Robert Jameson.) Edinburgh. Vol. I, pp. 133-134. 1876. Peck, C. H.— The black spruce. . Hopkins, A. D. — Some insects injurious to forests. The locust borer. roof that they were finding weevils was obtained. Observa- tions in the summer suggest the possibility that they may have been searching for larvae which had fallen from leaders stripped by other birds. The various field mice, shrews and wood mice, are insect eaters, and the fact that runways can be found in the litter at the depth where the weevils hibernate is a good indication that they very probably take their toll of the weevils during the hibernation period. The White Pine Weevil — Its Biology and Control 57 Prevention of Attack by the Insect Prevention of attack by the white pine weevil means the saving- of the leader and consequently a straight stem at all times. The two methods tried by the writer are (1) spraying with repellents and (2) banding the leader with some material which will prevent the weevil from reaching it except by flying directly to it. Sprays and Repellents Experiments have been carried on by at least three other in- vestigators in different parts of the weevil's range to determine the feasibility of stomach poisons and repellents as measures of control. Good results, as repellents, have been obtained by the writer with lime sulphur in a proportion of ten ounces to eight quarts of water, and with lead arsenate in a proportion of two ounces to eight quarts of water. In each case calcium caseinate was added as a sticker and spreader. The cost of spraying has not been given b}" Walden (1915) or Graham (1926), but the writer found that for lead arsenate it was $1.45 and for lime sulphur it was $1.70 per acre. The cost is mostly for labor as both materials are relatively inexpensive. The use of a good adhesive agent in the spray mix- ture is necessary so that the film of spray will stick to the leader for the entire period of oviposition. The area treated by the writer was about three acres in extent, and was divided into strips. In all the sprayed strips the infestation was reduced about one- half, although the infestation in this particular area was very low — 3 per cent on the check strips, 1.7 per cent on the strips sprayed with lime sulphur, and 1.1 per cent on the strips sprayed with the lead arsenate. Up to the time of a heavy rainstorm the percentage of infestation was negligible and no feeding punctures M-ere found. This rain washed off the material and practically all the weeviling happened after this storm. Considerable waste of material was unavoidable as there were no spray nozzles obtainable that would make a "mist-spray" and still concentrate the material in a small stream. Britton and Walden (1911), in addition to the work done with lime sulphur and lead arsenate, experimented with other mate- rials, but on a small scale. Of these, whale-oil soap, in a propor- tion of eight ounces to one gallon of water, gave good results with no injury to the leaders, but is more expensive to use than either of the other materials mentioned above. Graham (1916 and 1926) reported experiments with sixteen different materials or mixtures and found only carbolineum and creosote, sprayed on pure, to be completely effective. He did not get good results with lime sul- phur, as did "Walden (1915) in Connecticut or the writer in Massa- chusetts. Walden sprayed over eight hundred trees and the writer over eleven hundred, while Graham sprayed only ten, and this may explain the difference in results. 58 The New York State College of Forestry If an effective repellant can be used economically it will mean the saving of the leader and consequently straight stems. At the present time the labor cost per acre per year is too great to allow widespread use of this method in plantations or natural stands. It will be an efficient and desirable means of control of ornamen- tal or shade trees, or in small plantations where the aesthetic' value is paramount. Banding Materials Banding the leaders with some material which wall prevent the weevils from getting to them, except on the wing, is very effective, but the bands must be renewed each season. The rate of weeviling is reduced in severe infestations very noticeabl3^ Two materials, sticky banding material and raw wool, have been used in this work, the bands in all cases being placed above the previous season's growth of laterals. Sticky tree-handmg material. As previously stated in the section on Flight Habits, the central plot of one series in a severely in- fested plantation had all trees banded with sticky tree-banding material just above the lateral growth of the previous year. In this plot the percentage of trees weeviled decreased from 51 in 1925 to 12 in 1926, while the average for the four check plots increased from 37 in 1925 to 57 in 1926. Thus, while the infesta- tion was very materially decreased in the treated area it was in- creasing in the check areas. The disadvantages encountered in using the sticky tree-banding material are that it lasts but one year, is very apt to become hardened by the weather and must therefore be inspected frequently, and the cost is prohibitive. The material is expensive and the labor charge will be at least $2.50 per acre per year. Raw WooL Four series of plots were laid out in 1927 in con- nection with the experiments with the wool bands. Two of these were at the Rainbow Plantations of the Connecticut Agricultural Experiment Station and the others were on the Choate Plantations at Petersham, Massachusetts. Each of the series of plots at Rainbow consisted of a central plot and four check plots, and all of the plots were one-twentieth acre in area. In one central plot the infestation, the year before the experiment was 3.4 per cent, w^hile the average for the check plots was 2.5 per cent. In 1927, the infestation in the treated plot decreased to 2.2 per cent, while the average for the check plots rose to 10.8 per 'cent. In 1928, the treated plot again had 2.2 per cent and the check plot average dropped to 4.1 per cent. In the other plot results were somewhat similar. The treated plot had 7.0 per cent infestation the year before the experiment, and the average for the four check plots was 3.3 per cent. No weevil- ings occurred in the treated plot in 1927, but, as in the previous The White Pine Weevil — Its Biology and Control 59 series of plots, the average infestation in 'the cheeks rose to 15.3 per cent. In 1928, the treated plot had 12.1 per cent infestation while that in the check plots was 8.1 per cent. These figures show a decrease in the treated plots of both series the year the leaders Avere banded (in one case to zero), and a distinct increase in the check plots. In 1928, the effectiveness of the bands was lost, as practically every band had been partially or wholly removed. One treated plot had the same percentage of infestation and the other had a very noticeable increase, while in both series of checks the infestation had decreased. The first series of plots at Petersham consisted 'of a central plot and four check plots, each one-tenth acre in size. The amount of weeviling the year before the experiment was not noted. In the treated plot the infestation in 1927 was 3.5 per cent, while the average for the 'checks was 17.5 per cent. In 1928, the infestation in the plot treated the season before rose to 18.6 per cent, and dropped to 14.6 per cent for the check plots. In the other series, seventy trees were taken in each plot. In 1927, the banded trees showed an infestation of 13.1 per cent, and that in the check trees was 55.1 per cent. ' In 1928, the infestation in the treated area was 18.8 per cent and was 21.0 per cent in the untreated area. ' It can be seen that the results obtained at Petersham were very similar to those obtained at Rainbow, in that there was a distinct decrease the year the bands were applied and the following year the infestation increased again in the treated plots, even though it decreased in the check areas. The disadvantages found in the wool bands are that the wool is removed by birds for nesting pur- poses, and it is almost imperative that it be tied to the leader to prevent the wind blowing it away. It was also found that it offers an excellent place for the deposition of eggs of the pine bark louse {Adelges pinicorticis Fitch) as each leader, around which a band remained over the winter, had a considerable number of the egg masses between the band and the bark. The cost of appli- cation, in this method, was about the same as with the tanglefoot. In both methods the taller the trees, the greater was the ' cost. If the material is not properly applied, it will not give protection — in other words the entire surface round each leader must be covered for at least an inch, and, in the case of the sticky banding material, it must be inspected periodically to see that it is retain- ing its sticky quality. This method is practical for ornamental and shade trees, but the raw wool in particular gives the leader an unsightly appearance. In extensive forest plantations, the cost of application will make this method prohibitive. 60 The New York State Colfege of Forestry Direct Control of the Insect As Graham (1926) points out "The direct methods of control are in their very nature rather expensive and are therefore limited in application to trees that have some value in addition to the wood produced. . . . Direct control is applicable to shade and orna- mental trees, to windbreaks along highways, on watersheds, and in some private forests where the aesthetic value is an important consideration. ' ' In young plantations it would appear from obser- vations and data collected that direct measures are feasible if the work is begun before weeviling becomes prevalent. The cost of such an operation over a period of years must be considered and it is doubtful if this increased financial burden, necessary to obtain minimum injury, would be considered by the average timberland owner, even though the operation, carried over year by year, in a lightly infested stand might not cost more than twenty-tive cents per acre per year. Three direct control methods have been tried, and all are, within the limits mentioned in the detailed account of each, effective. These methods are: (1) picking the beetles by hand, (2) jarring the insects into a net, and (3) removal of the infested leaders. Picking the Beetles by Hand One instance of picking the beetles from the leaders has been reported to the writer. Many of the trees in a plantation of about five acres on the Choate Estate at Petersham were being attacked severely in the spring of 1923. These trees were about six to eight feet high, and the leaders could be reached quite easily. The caretaker and one other man spent a considerable time going from tree to tree in each row and picking off the weevils which they saw. Their work was very carefully done and the attack was noticeabl}^ checked for two years. The cost was not considered for this opera- tion, but it is estimated, on a basis of 50 cents per man hour to have been about $2.50 per acre. This method is limited to trees within reach of a man's hand, and, as it must be very carefully done in order that the beetles will not drop off, is not practical economically. Jarring the Insect into a Net The collections of the adults from the leaders during the period preceding egg-laying in the spring has often been advanced as a means of control. Walden (1914) and Felt (1916) have re- ported that a considerable reduction of weevils in plantations is possible. In Connecticut, Walden found that six collections, about a week apart, cost between $1.50 and $2.00 per acre. Felt gives the cost in an operation in New York as $1.28 per acre. Both these cases, however, were at a period when the labor cost The White Pine Weevil—Its Biology and Control 61 Avas not as high as at present. The feeding period for aii indi- vidual female is very short — not over a week — and great care must be exercised to get all the weevils. Several collections must necessarily be made in each stand or plantation, as the weevils do not emerge from hibernation simultaneously. There is also the probability of immigration from outside infested areas when flying is generally possible. As the adults feed upon and take refuge among the buds during unseasonable weather, these must be examined and any weevils found re- moved. Jarring the leader on one side with a fairly heavy stick so as to knock the weevils off into a net held on the opposite side is the only practicable way to collect those on the leader itself. However, when the w^eevils are in the bud clusters, they cannot be dislodged in this manner, but must be picked out. This method is practical with ornamentals and possibly with young plantations isolated from native pine which is in- fested, or of value aesthetically. The cost in an extensive planta- tion or over a wide area, however, is prohibitive. In addition to this, once the trees get above seven or eight feet in height, the leaders are too high to be reached without the aid of a step- ladder or box. Removal of the Infested Leaders The removal of the infested leaders after they have wilted has been recommended for many years as an excellent means of con- trol. In areas where there is natural pine in the surrounding country, from which the treated areas could be reinfested, this is financially impractical in either forest plantations or natural stands. Where there is a scarcity of pine nearby or where the plantations have aesthetic value, removal of the leaders is prac- tical only so long as they can be reached by hand. It will be necessary to go over the stand at least twice each season; the second time to remove those leaders which were missed the first time as well as those which wilted after the first operation. The leaders as they are removed must either be burned or placed in tight receptacles. Burning is the one certain means of killing all the larvae and pupae of the weevil, but if the leaders are placed in tight receptacles, screened on at least one side, and left in the plantation, the smaller parasites will not be killed. These receptacles should be so placed that water will not collect in them and drown the parasites. They should be left in the plantation until the following spring. By this time all the weevils will have died, the screen can be removed and those parasites which have hibernated in the tunnels of the weeviled leaders will be able to escape into the plantation. The use of number twelve or fourteen mesh screening is advisable, as these meshes will allow the escape of practically all the parasites, some of which 62 The New York State College of Forestry are too large to escape through the number sixteen mesh, which is the size which has heretofore been used. This method is not practical in forest plantations, where there is a liability of reinfestation from surrounding areas, as the cost of removal often exceeds a dollar per acre per year. In order to have anj^ appreciable effect, it must be carried on over a period of years. Below eight feet, the cost should not be more than twenty-five cents per acre per year to be of economic value. Above this height, the cost will be greater, depending on the height of the trees and the amount of the infestation. The total cost of the operation up to the time the trees are thirty feet high would amount to a considerable sum at compound interest by the end of even a short rotation ; but the increasing value of the stand may, in some cases, warrant the expenditure. Results obtained by the removal of infested leaders from a number of plantations in the Petersham area for two or three years have yielded some interesting data. In five heavily infested areas, treated for three years, two showed an average decrease in number of weevilings of 38.9 per cent the second year and 50.7 per cent the third year. Check plots in plantations adjacent to the treated ones showing decreases, showed an average infestation the first year the leaders were removed of 27.4 per cent. The second year this rose to 44.2 per cent and the third year it was 38.0 per cent. The infestation, therefore; was greater by 61.3 per cent the second year and by 38.6 per cent the third year, while it was decreasing in the treated plots. In the re- maining three there was an average increase of 57.2 per cent the second year and of 41.7 per cent the third year. The average decrease for all five plantations for the two years was 17.9 per cent and 30.5 per cent respectively. In stands which are isolated and which have a small amount of infestation, treating the leaders is practical. The cost should not be excessive in such isolated areas if carried on from year to year from the time the trees are liable to weeviling. If not begun until several years after the weevils first get into the stand, as happened in the first five plantations treated, the weevils become established and the cost will be much greater than if begun the first year. In South Carolina and in parts of Ontario and Quebec infestations were completely controlled by the removal of the wilted leaders before the adults emerged from them. At Rockwell Springs Experiment Station, near Syracuse, New York, the infestation in a plantation spaced 3' x 3' has been kept down to a total of less than two per cent over a period of ten years through the annual removal of the infested leaders. The importance of the second inspection each year is borne out by the following incident. On the Swann State Forest in The White Pine Weevil — Its Biology and Control 63 Western Massachusetts, the removal of leaders has been prac- ticed extensively for a period of years. Over an area of eighty- five acres of young white pine, the infestation, the second year after the removal operation began, was only 1 per cent. The cost of removal of the weeviled leaders for the third year was only eleven cents per acre. However, a number of the leaders were missed the next year and the cost had risen to twenty- six cents per acre. No check areas were available for com- parison. The amount of crook which will necessarily occur can be largely overcome by an additional operation which can be performed at the time the leaders are removed, with very little additional labor. The bud clusters on all but one lateral should be removed by pinching or clipping. This seems to result in the remaining lateral absorbing all the available nutrient materials which would have gone to the other laterals as well as the amount it would normally have used itself, thus giving an extra stimulus for growth. Removing the bud clusters does not impair the growth efficiency as much as if the entire length of each lateral was removed. In other words, the amount of leaf surface is not re- duced to the extent that it would be if each entire lateral were removed. The laterals so treated do not grow at all in length and not appreciably in diameter ; and there is no wound such as would occur if they they were removed at their bases. The effect on the futui'e quality of the timber will also be better in those trees where the laterals are left — there will be small knots, but they will probably be tight. Repair of the Injury by Silvicultural Methods The information gained in studying the sample plots is in accord with that secured from previous studies by Hopkins (1907), Blackman (1916, 1919), Fisher and Terry (1920), Pierson (1922), and Graham (1926), in indicating clearly that under certain forest conditions the injury, as well as the severity of attack, may be substantially decreased. Permanent injury is found most fre- quently in stands which are below par in site and density. It can not be expected that a stand will be free from insect or other injury unless it is maintained at a reasonable standard of density and vigor. Repair of the injury will be considered from two angles — (1) density of stocking in pure stands, and (2) produc- tion of mixed stands. Density of Stocking Under optimum site conditions, density of stocking will tend to keep permanent injury by the weevil at a minimum. Such a stand, however, is financially practical only when it can be procured naturally, and at a high enough density to offset any weeviling 64 The New York State College of Forestry which may occur (Plate XI-1) Pierson (1922) and Graham (1926) state that this minimum amount of damage can be ex- pected at the end of the rotation, if a fully-stocked stand of from 1,200 to 1,500 trees per acre is maintained throughout the early years and, thereafter, a fully-stocked stand according to age class requirements. The writer's observations show that this will hold only where there is not a very severe infestation. Where there is an average infestation every year of nearly 50 per cent, as is often the case in the "weevil country" of central Massachusetts, it w^ould appear that a greater number of trees per acre is neces- sary, even when the trees are fifteen years old in plantations of those densities. In the main, however, if this density is not main- tained, it will be below the standard necessary to produce a good crop. Throughout the range where it can reproduce itself in pure stands on abandoned lands, there are many thousands of acres of old field pine which are in good condition. In these stands the site conditions and stockings are such that the trees are vigorous. Sparsely-spaced stands, such as those which often come in on medium soil in abandoned pastures, will generally be weeviled quite heavily. In a closely-spaced stand only a relatively small number of trees will be in the dominant or codominant height classes at fifteen years of age; and, after a stand has reached a height of thirty feet, it will be necessary to remove the dead and suppressed trees. This will improve the condition of the stand and allow the remaining trees to develop more rapidly. The denser the stand, the greater will be the tendency to pro- duce relatively straight stems when weeviling does occur in such stands. In Graphs VI and VII, it will also be seen that in pure stands, both natural and artificial, growth conditions being similar, the greater the number of trees per acre the less will be the per- centage of weeviling. Graph VI shows the cumulative increase in number of trees weeviled from year to year in four plots in adjacent pure plantations where the spacings are 6' x 6', 5' x 5', 4' x 4', and 3' x 3'. The same number of trees were examined i]i all four plots and the site conditions are practically equal. In addition to the marked decrease in weeviling, the 3' x 3' plantation has only 12.1 per cent of the weeviled trees attacked more than once; while the 4' x 4' has 27.7 per cent; the 5' x 5' has 30.1 per cent; and the 6' x 6' has 40.9 per cent. The material for this graph was obtained from an acre plantation on the Harvard Forest. The plantation is divided into blocks of one-quarter acre each, with a different density, as previously stated, in each. Graph VII shows the amount of weeviling in white pine in pure stands and mixed stands of the same age, and "under similar site conditions. The white pine -was planted in densities of 8' x 8', The White Pine Weevil — Its Biology and Control 65 6' X 6', and 4' x 4' under gray birch, aspen and fire cherry in 1916. Half of each area was released in 1922, so for six years there has been a condition approximating a pure stand while in the re- mainder the mixed condition has persisted. Each plot is one- quarter acre in size and all trees were taken in each one. By comparing the results as shown in the curves it is apparent that there is considerably less weeviling in the mixed stand than in the pure stand. The possibility of controlling the weevil injury by dense plant- ings is impractical from a financial standpoint. The cost of plant- ing in closer spacing than 6' x 6' makes plantations denser than that prohibitive. At the present time, in the majority of localities, a spacing which will give more than 1,500 trees per acre is not considered in planning for a future forest, unless it can be secured naturally. However, it appears that on light sandy soil, where the ultimate weevil injury is usually not so severe as on the old field, medium soils, a densely stocked stand for ornamental or aesthetic purposes would be practical. There are disadvantages with which the forest owner will have to contend if a pure stand is to be produced. AVhen trees in the intermediate and .suppressed crown classes are weeviled they are generally left behind and will eventually die. Lack of natural pruning in a pure stand is also a disadvantage. The lower branches will die in such a stand but they will persist for years instead of falling off. The knots in the lumber produced will be small, but there will be very little clear lumber at the end of a sixty year rotation. While these disadvantages may not be considered as important as the high cost of the original planting they are factors which must be considered if high grade lumber is expected at the end of the rotation. Mixed Stands The plots laid out in the different parts of the Northeast have yielded abundant proof that the most advantageous way to pro- tect white pine from the weevil is to grow it in mixture, prefer- ably with species that will be of value in the final crop. These species may be either coniferous or broadleaved trees, the latter in any case depending almost entirely on the economic conditions in that particular locality. There will not be so many white pines in a mature mixed stand as in a pure white pine stand, but a larger percentage of those surviving will be clean-boled and straight. In a region heavily infested w^ith weevils it is very probable that comparatively little of the pure pasture pine or the trees in widely- spaced pure plantations will be straight and free enough of limbs to produce high grade timber. The maximum amount of protection, and subsequently the maxi- mum amount of good lumber, will be found where there is a 66 The New York State College of Forestry •iTOupwise mixture of white pine and the better hardwoods (Plate XI-2). In a stemwise mixture, there is danger of whipping, w^hich, in its damage to the leading shoots, may be almost or quite as injurious as the white pine weevil. Previous investigators have suggested that the reason for the protection afforded by these mixed stand.s is the shading of the species liable to attack and the mechanical barrier against flight caused by the accompanying species. The leaves of the broadleaved species are still on the trees when the fall migration takes place and this barrier action is one of the reasons why the species liable to attack are not infested to any extent even though pure white pine stands nearby may be severely injured. The odor from the smaller number of pine trees in a mixed stand will not attract as many weevils as will the odor from a greater number of trees in a pure stand concentrated in an area of the same size. The preference, shown by the weevils, for feeding and ovi- ])ositing in leaders from pure open stands is also a factor which must be considered, as we have already seen. There is also evidence to show that in many cases the white pine leaders, although attacked, may recover, and very few weevils, if any, develop in those which are killed. This is undoubtedly due to the fact that there are usually fewer eggs laid in such leaders, and the small number of larvae are more likely to be smothered by the resin. If accelerated height growtli has begun this is especially likely to occur. Weedings in the early stages, if the mixture be with hard- woods, and thinnings as the stand becomes older, will be neces- sary so that the white pine will not be crowded out. By judicious weeding the groups of the species liable to attack, such as the white pine, can be kept fairly well regregated and the final stand will contain groups of much better quality than can be grown in the pure stands. Aside from the protection offered, an advantage in growing white pine in mixture with other species is that it cleans itself relatively early in life, and the boles will be clear for some distance. As stated in the Summarization of Plot Data, an alternate row mixture of the white pine and the Scotch pine has given maximum protection against weevil attack and also favors the repair of the injury when attack does occur. A natural mixture of the Canada hemlock and the white pine gives good protection to the latter species if the hemlocks are several years older and therefore several feet high at the time the white pines begin to grow (Plate XII). In fact this protection can be obtained in any coniferous mix- ture, whether it be an artificial planting in alternate rows or a natural regeneration, groupwise or stemwise in composition. The accompanying species, however, must be immune from The White Fine Weevil — Its Biology and Control 67 weeviling and faster fjrowinir in the earlier years, if both are the same age, or if slower growing it must be considerably older, at the time the white pines become liable to attack, so that it will be taller than the latter. There will be little danger of whipping in sneh stands if the leaders of the white pines are high enough to be above the spreading branches in the lower part of the crowns and still be at least two or three feet below the leaders of the accompanying species. The disadvantage met with in the regeneration of a coniferous mixture is that there will be no protection offered if the white pines are as tall as the other species. Application of Control Measures to All Species Liable to Attack Protection of the white pine has been emphasized in these control measures because this species is the favored host of the white pine weevil and is the most widely planted or naturally regenerated species, in the range of this insect, of those which are susceptible to attack. Norway spruce, which is damaged to almost as gi-eat an extent as the Avhite pine (Plate XTII-2), is grown in large plantations, and the injury can be minimized by the same measures. All the other species which are attacked by the White Pine Weevil can be protected against infestation. Those measures given for ornamental and shade trees are par- ticularly applicable for the exotic species which are planted for these purposes. SUMMARY The White Pine Weevil (Pissodes strohi Peck) is the most seri- ous insect pest attacking the white pine (Pinus strohus L.). The leading shoot is killed, resulting in loss in height, loss in radial increment and often poor form. The timber value is also ma- terially affected ; lumber sawn from weeviled trees will usually show large knots at the points of weeviling, and very often decay will be present. Short lengths will often be necessary because of the many crooks in the stems due to weevil iniury. The adult weevils hibernate mostly in the lowest layer of the litter, just at the surface of the mineral soil under trees fed on during the fall. Occasionally they hibernate at the bases of trees cut during the late summer or fall. The trees fed upon during the fall may or may not have been weeviled that season. Young adults and even full-grown larvae from eggs laid late in the season may, under very favorable conditions, hibernate in the leaders. The weevils emerge from hibernation in the spring about the time the buds begin to swell, and activity apparently ceases with the cessation of accelerated aerial elongation, as no weevils are found from this time until the new generation emerges. This 68 The New York State College of Forestry period depends on the growing season and weather conditions. The females may be fertilized in the fall, as well as in the spring. Oviposition begins soon after activity is resumed, reaches the peak in two to three weeks and then gradually diminishes, ending with the cessation of activity of the old adults. Development from the egg to the adult covers a period of approximately three months. The new generation emerges in the late summer and feeds on the tender inner bark of the tips of branches and lead- ing shoots, but does little damage as compared to that done in the spring. Feeding ordinarily goes on at intervals until settled cold weather prevails, and then the weevils go into hibernation. The adult weevils, in both spring and fall, are relatively strong fliers. They can cover considerable distances when wafted by the wind, and can thus reinfest an area or infest a new area in a short time. The air temperature necessary for general flight appears to be between 70° and 85° Fahrenheit. Above and be- low this range, comparatively little flight has been observed. Both sexes will fly directly to the leading shoot, but the majority strike the trees lower down and crawl up the stem. In the early spring, before warm weather prevails, many of the weevils reach lead- ing shoots by crawling up from the ground. The degree of intensity of infestation depends primarily on the number of host trees available, weather factors (chiefly tem- perature), soil conditions and exposure. Adults feed and ovi- posit more readily on trees in pure, widely-spaced stands than on trees in dense, pure stands or in mixed stands of pine and other species, such as hemlock or hardwoods. Stands on medium agricultural (sandy loam) soils will generally show the most injury. Stands on sandy soils may have as many trees weeviled per acre, but the ultimate injury is not so severe. Plantations or stands on sunny exposures are more liable to weeviling than those on exposures protected from the morning sun. Direct control measures are generally too expensive for com- mon practice. In isolated stands, where the infestation is low and the danger of reinfestation is slight, or in stands which are being preserved for their aesthetic value, such control measures may be used advantageously. Weeviling, in stands which are subject to attack from surround- ing areas year after year, can sometimes be checked, but not con- trolled, by the removal of the infested leaders, collection of the, adults during the spring feeding period, spraying with repellents or banding the leaders. The cost of these treatments, often more than a dollar per acre per year makes these measures prohibitive over wide forested areas. The breeding and liberation of parasites and predatory insects in infested areas is an uncertain measure of control. The cost, necessary for breeding and liberating a number sufficient to have The White Pine Weevil — Its Biology and Control 69 an appreciable effect, would be too great to make such a project financially practical over a "wide area at the present time. Insectivorous birds are very valuable natural control agencies and they should be protected and encouraged in pine woodlands. In pure stands, both natural and artificial, the greater the num- ber of trees per acre the smaller will be the percentage of weevil- ing. A dense stand is financially practical only when it can be procured naturally at a high enough density to offset any weevil- ing which may occur. Where site conditions and the stocking are favorable for vigorous growth good stands of merchantable old field pine are common. The most advantageous and cheapest way to protect white pine from the weevil and to control the injury is to grow it in mixture, preferably with species that will be of value in the final crop. The choice of the other species wiU be determined by the economic conditions in any given locality. Weedings in the early stages, if the mixture be with hardwoods, and thinnings as the stand becomes older, will be necessary so that the pines will not be crowded out. There will not be so many white pines in a mature mixed stand, as in a mature pure stand of normal stocking, but those present will be clean boled and straight, and the value of the whole crop will be greater. 70 The New York iStotc College of Forestry BIBLIOGRAPHY Anon., 1921. \Vliite Pine Weevil and Eeforcstation. The Con-servatiouist. Vol. IV, j)p. 189-100. Anon., 1925. White Pine Weevil. Cons. Conun. N. 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Stone, and H. T. Fernald. Mass. Agri, Expt. Sta. Bull. 125, p. 58. Femald, H. T., 1921, The White Pine Weevil {Pissodes strohi Peck). App. Ent., pp. 142-143. Fisher, R. T., and Terry, E. I., 1920. The :Managenieut of tSecond Growth White Pine in Central New England. Jour. For. IV, pp. 358-367. Fitch, A.. 1858. iV Kept, on the Noxious and Other Insects of the State of New York, pp. 732-730. Forbush, E. N., 1913. Useful Birds and Their Protection. Mass. State Bd. of Agri., pp. 168, 254-256. Franklin, H. J., 1921. Keference to species of Fhygadeuon on the Cranberry Girdler in Report of the Cranberry Station for 1919. Mass. Expt. Sta. Bull. 206, pp. 149-168. Frothingham, E. H., 1914. White Pine Under Forest Management. U. S. D. A. Bull. 13, pp. 62-63. Fuller, A. S., 1870. Wliite Pine Weevil. Am. Ent. Vol. II, p. 26. Fuller, A. S., 1880. A Good Word for the White Pine Weevil. Am. Ent. and Bot. Vol. III. (2nd Series 1), pp. '5-6. Germar, E. F., 1817. Magazin der Entomologie. 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Riley, C. V., and Howard, L. 0., 1891. The White Pine Weevil. Ins. Life, Vol III, p. 468. 76 The New York State College of Forestry Say, T., 1831. Descriptions of North American Curculionides, and an Arrangement of Some of our own Species Agreeably to the Method of Schonherr. New Harmony, Indiana. The Complete Writings of Thomas Say on the Entomology of North America. Pissodes (Rhynchaenus) strobi, Peck. Saunders, W., 1883. Insects Injurious to the White Pine — Pinus strobus. Ent. Soc. Ont., p. 55. Simmons, J. R., 1916. Three Common Dangers to White Pine. New England Homestead, Vol. LXXII, No. 2, p. 5. Smith, R. C, 1921. Reference to Muscina stabulans Fall in "Observations on the Fall Army W^jrm and Some Control Experiments." Jour. Econ. Ent. XIV, No. 3, pp. 300-305. Spaeth, J. N., 1922. Notes on .Release of White Pine on Harvard Forest. Jour. For. Vol. XX, No. 2, pp. 117-122. Spring, S. N., 1905. The Natural Replacement of White Pine on Old Fields in New England. U. S. D. A. Bur. of For. Bull. 63, pp. 14-15. Steams, L. A., 1919. Reference to Rhogas species in "Some Recently Recorded Parasites of the Oriental Peach Moth." Jour. Econ. Ent. XII, No. 4, pp. 347-348. Swaine, J. M., 1925. The Destruction of Canadian Forests by Insects. Pulp and Paper Magazine, June 25, p. 725. Swaine, J. M,, 1928. Forest Entomology and its Development in Canada. Dom. Can. Dept. Agri. Pamphlet 97, pp. 4, 16, 19. Tarbox, E. E., 1924. Quality and Growth of White Pine as Influenced by Density, Site, and Associated Species. Harvard Forest Bull. 7. Taylor, R. L., 1927. A New Species of Parasitic Hymenoptera {Chalcidoidea, Eupelmidea) . Brooklyn Ent. Soc. Vol. XXII, No. 4, pp. 205-207. Taylor, R. L., 1928. A New Species of Lonchaea Fallen (Lonchaeidae Diptera). Bull. Brook- )yn Ent. Soc. October, p. 191. Taylor, R. L., 1929. The Arthropod Fauna of Coniferous Leaders Weeviled by Pissodes strobi (Peck). Contribution from the Entomological Laboratory of the Bussey Institution, Harvard University, No. 301 Psyche, Vol. XXXV, No. 4, pp. 217-225. Thomas, C, 1874. VI Rept. of the State Entomologist on the Noxious and Beneficial Insects of the State of Illinois, pp. 133-134. The White Pine Weevil — lis Biology and Control 77 Vierick, H. L., et al., 1916. The Hymenoptera, or Wasp-like insects of Connecticut. State Geol. and Nat. Hist. Survey of Conn. Bull. 22, pp. 210, 765. Walden, B. H., 1914. XIV Rept. State Entomologist. Conn. Agri. Expt. Sta. Bull., pp. 173-176. Walden, B. H., 1914. Experiments in Controlling the White Pine Weevil in 1915. XV Rept. State Entomologist. Conn. Agri. Expt. Sta. Bull., pp. 134-136. Walker, E. M., 1911. Some Injurious Insects at De Grassi Point, Lake Simooe. Rept. Ent. Soc. Ont., p. 58. Webber, R, T., and Schaffner, J. V. Jr., 1926. Host Relations of Compsilura concinnata Meigen, an Important Tachinid Parasite of the Gipsv Moth and Brown-Tail Moth. U. S. D. A. Bull. 1363, p. 27. Weiss, H. B., 1919. White Pine Weevil {Pissodes strobi Peck). State Bd. of Agri., State of New Jersey, Cir. 5. Wells, A. B., 1926. Notes on Eylobius pales Herbst and Pissodes strobi Peck as Nursery Pests. Jour. Econ. Ent. Vol. XIX, No. 2, pp. 412-413. Wheeler, W. M., 1913. Reference to Pheidole species in "Ants — Their Structure, Development and Behavior," p. 268. EXPLANATION OF GRAPHS APR. 26 MAY JUNE JULY I? 24 31 7 14 21 29 5 12 19 26 2 Da/es Measuremen/s irere maf Chei k Trei 'S. / / / /, '/ I A / ^ 10 lYear Year lYear 2 Years Stfears 4Years beFore of affer after after after Wvl'^. Wvl-^. Wvl;^. Wvl;^. Wvl;^. Wvl-^. Years of Grrowih Graph II. To show the Ap])roxiinate Loss in Height Growth of Trees killed back two years, each time a Tree is Weeviled. Based on 60 Weeviled Trees and 60 Non-weeviled Trees. [82] 10 9 r I' >? 6 —— 53 Trees 79 Trees M Trees jarree / y y ^ / / y / / 'A / / V A / A // / / ^ / ,/ / 34 rrt^ s / ^ Trees "'ei Trees 45 Trees 6i , ^ ^ 4^ .- ..- ->, ^w ^« ^^w /^^ WV^ Height ahoye ground in fee/. Graph III. To show tlie Contrast between the Average Number of Weevilings per Tree Weeviled in the Different Height Classes in White Pine from Stands of low density pure old field pine and from Stands of mixed white pine and hardwoods. The broken linea indicate trees from mixed stands. [83] 24- 11 20 18 16 14 12 10 //^/^/4/ of Sco/^ ■ft Pine. / // '^//s "~~~- •Z5 zo 30 40 60 70 80 50 fie/gf?/ C/asses. Graph V. To show the Average Number of Weevilings per Tree below 25 and 35 Feet in all Height Classes. Pure old field pine, low density, all aged. E-xplanation in Text. [85] ^ •^ 80 no 60 50 40 30 20 10 -6x6 ^^ X -^ -3«5 y ^ '4'4 y ^ ^^^ /. ^x ^ >/ V -^ — -30 z. ^ -^ (t 1917 1918 1919 1920 1921 1922 1923 IQOi 1925 1926 1927 1928 Graph VI. Comparison of the Cumulative Increase in Percentage of Trees Weeviled in Pure stands of Different Densities. Based on 125 Trees from each plot. [870 5 60 I >,50 1 I 40 IP 5! 30 ^ zo 10 ^RnR ^ ^ B y^ ^6 "6 ■^ r::: t^ '4'4 1916 1917 1918 1919 1920 1921 1922 1923 1924 1925 1926 I9Z7 1928 Years of (rroyyih Graph VII. Comparison of the Percentage of Trees Weeviled in Stands of Different Densities. Explanation in Text. A — White Pine from Pnre Stand. B — \^^lite Pine from Stemwise Mixture. [87] EXPLANATION OF PLATES PLATE I Type of Cage used in lv\|i('iiiiu'iits (o Dctciiniiic the Averayo Nuiiilier of Eggs laid by each FemaU-. PLATE I PLATE II 1. Sliowing tlie Positions tlio Pupae may assiinio wliile in their Pupal Chambers. 2 and 3. Showing the Position and Character of tlie Pupal Chambers in the Pith and in the Wood. 4. The Dried Pitch Masses on a Weeviled Leader. PLATE 11 PLATE III A Weeviled Leader. PLATE III PLATE IV A Plantation showing the Bayonetted Effect on Weeviled Trees. (Courtesy Harvard Forest. ) PLATE IV PLATE V 1. A Badly Forked Tree. 2. Staghorn Pine, showing several Weevilings in each Tree and the Resulting Staghorn Effect. (Courtesy Harvard Forest.) 3. A Weeviled Tip which has persisted for Many Years in a Log whicli was 12 Inches in Diameter at the Weeviled Point at Time of Cutting. Exit Holes are Plainlv Evident. PLATE V PLATE VI 1. An Uniujurt'd Tree. (Courtesy G. H. Lentz. ) 2. A Typical Cabbage Pine. (Courtesy Harvard Forest.) PLATE VI ^■;«...... PLATE VII 1 and 2. Boards with Knots to the (A'liter. Tin- Kesnlt of Weeviling. 3. Board showing Clear Portion on One Side; Knots on Opposite Side aic due to Weevling. 4. Board showing Large Knot and Persisting Leader after Wee\ iling. PLATE VII PLATE VIII 1. iShowiiig Knots on One Side of Board due to Weeviling; Clear Portion on Opposite Side. 2 and 3. Showing; Decav following Weeviling. PLATE VIII PLATE IX Injuries Often Mistaken for Weeviling. 1. A Dead Leader in Sfoteli Pine caused liy Weather Injury. Tlie Absence of Exit Holes Distinjiuishes this Injury from \Veevilin<;. (Courtesy G. A. Whipple.) 2. White Pine Trees oveilojiped and -wliiiiix'd liy Oiay Birch. 'A. Squirrel Damage. A C'look or Fork results fioni this Injury and may often be mistaken for \\'ee\ ilinu. (Courtesy Harvard Forest. I PLATE X 1 and 2. Larvae of Lo)whaea corticis T. in the Larval Tunnels and Pupal Cliambers of Pissodes strobi Peck. (See also Plate II-l.) 3. A Lepidopterous Larva in the Pupal Chamber of Pissodes strobi Peck. 4 and 5. Showing tlie Bark Stripped from Weeviled Leaders by Birds in order that the Larvae and Pupae may be eaten. PLATE XI Sliowiiit; Density of Tree in a Pure Stand. Resulting in .Mininuiin Injury. (Courtesy HarAai'd Forest.) Mixed White Pine and Hemlock showing Straight Pines without Weevil Injury. (Courtesy Harvard Forest.) PLATE XI PLATE XIII 1. A Paint Brush Top in Scotch Pine caused bv Weatlier Tniurv. (C'ourtesv G. A. Whipple.) 2. Weeviling in Norway Spruce. PLATE XIII Bulletin 449 June, 1926 Biology and Control of the White -Pine Weevil, Pissodes strobi Peck Samuel A. Graham AN ADULT WEEVIL ON A BUD CLUSTER OF WHITE PINE The feeding punctures show on the buds Published by the Cornell University Agricultural Experiment Station Ithaca, New York Received for publication January II, 1926 CONTENTS PAGE Injurious habits 4 Character of the injury . . ; ; .' . . ..^ 4 Host trees . ; 7 Relation of injury to age and height of tree 7 Relation of injury to crown class and rate of growth 8 Life history and habits 10 Activities of the old adults 10 Developmental stages 13 Activities of the young adults 15 Control 17 Direct control 17 Chemical methods 18 Mechanical methods 18 Indirect control 21 Silvicultural methods 21 Biological methods 26 Summary 28 Bibliography 30 BIOLOGY AND CONTROL OF THE WHITE-PINE WEEVIL, PISSODES STROBI PECK Samuel A. Graham The white-pine weevil is one of the most destructive pests of the eastern white pine. In some locahties the planting of this tree has been practically abandoned because of its ravages, and throughout the range of its host tree it has been a large factor in discouraging private reforestation of waste lands. It is therefore an important forest insect, not only because of the actual damage that it does, but also because of the bad psychological effect which its presence produces upon owners of forest properties where white pine is an important tree. This weevil was early brought to the attention of entomologists, and evidently it has always been an important forest insect throughout the range of the eastern white pine. The earliest observers of the insect found that to a certain degree it was controlled by several parasites. Peck (1817) states that " our forests would scarce produce a single mast " were it not for this controlling factor. Today, although the demand for masts is a small item in the white-pine trade, the merchantable value of the timber still depends on the straightness of the main stem, and any' crook or deformity such as that caused by the weevil reduces the value of the timber. Peck described this weevil in 181 7 and made a few notes on its life history. Since that time it has been studied by a number of entomologists, each of whom has contributed more or less to the knowledge of the species. Unfortunately, the white-pine weevil has been confused with some of its close relatives. This has led to many misleading, and even incorrect, statements concerning its life history and habits. One of the purposes, therefore, of the experiments upon which this paper is based, was to determine the true life cycle and habits of the insect as distinguished from those of its close relatives. T^e second and more important purpose was to find, if possible, some practical methods of controlling the weevil. The study was begun in 19 15 as a thesis problem under the direction of Professor Glenn W. Herrick, of Cornell University, and the greater part of the biological data included in this bulletin were collected at Ithaca during the summer of 1915. During 1916, most of these observations were checked and further work on the control problem was conducted at Ithaca and also on the Luther Forest Preserve near Saratoga Springs, New York, for the Department of Forestry at Cornell University. In 19 1 7 and 19 18, further studies were carried on in Isanti County and other localities in Minnesota, for the Minnesota Agricultural Experiment Station. Some of the results of the Minnesota studies have appeared in an article in the Journal of Forestry (Graham, 1918). Thus there has been opportunity to check results in several widely separated localities. In this bulletin 'an attempt is made to collect all of these data into a comprehensive whole. 3 4 Bulletin 449 INJURIOUS HABITS CHARACTER OF THE INJURY The injtiry done by the white-pine weevil is confined to the terminal part of sapling pines. The lateral branches are seldom injured. From a point just below the terminal bud cluster, the larvae work downward in the inner bark and girdle the shoot as they progress. The injury Figure i. leading shoot killed by white-pine weevils usually extends to a point below the topmost whorl of branches only, but many instances have been observed in which the tree has been killed below the second, or even the third, whorl from the top (figure i). When thejleader is destroyed in this way, the laterals in the topmost living whorl of branches compete for supremacy. In some instances one lateral succeeds in overtopping the others and takes the lead, and in such a case the tree either outgrows the injury or a bayonet trunk results. Sometimes, however, two or more laterals may take the lead, and produce a forked tree. In some cases weevil injury may render the.trees commercially valueless. Biology and Control of the White-Pine Weevil 5 Even where a single lateral takes the place of the killed leader and the tree outgrows completely the weevil injury, there is always a loss in height growth. If the leader is not killed below the first whorl, this loss is only the difference between the length of the terminal and the length of the lateral that takes its place. This difference varies in proportion 28 / 26 / 24 / / / / ^20 \ /2 \. C: /O Vi N 6 4 2 / / / r / y / / / / / / / / / / 2 3 4 6 (> 7 8 9 /O // Sxeess Of term /n a/ oyer /at era/, in inc/ies /2 Figure 2. relation between the length of the leading shoot (termin.\l), and the average excess of the le.\der over the corresponding lateral to the rate of height growth. The relation between the length of the leading shoot and the average e.^Lcess of the length of the leader over that of the corresponding lateral, is shown in figure 2. If, however, the weevil girdles the tree below the topmost whorl, the loss in height is equal to the difference between the length of the main stem above the topmost living whorl and the length of the lateral that assumes the lead. The average loss per tree, in feet, at different densities of the stand, is shown 6 Bulletin 449 in figure 3. The niimber of trees per acre as indicated on this graph, is the original number before any thinning or crowding-out has taken place. 9000 aUOO buuu Q. \ */U00 \ 1 5 ^nnn \ \ 9A/)/) \ ZUUU \ \, j/inA \ \ "^ ^^ "^ ■^ -- 0.50 /.OO /.50 2.00 2.50 Average /oss per tree, in feet Z.00 Figure 3. AVERAGE LOSS IN HEIGHT GROWTH PER TREE, IN FEET, RESULTING FROM WEEVIL ATTACK AT DIFFERENT DENSITIES It has been estimated that from 70 to 90 per cent of all the white pines in New York and New England have been weeviled before they have reached the age of fifteen years. In Minnesota this percentage is some- what lower. Unless steps are taken either to reduce this injury to the minimum or to assist the trees in outgrowing the resultant deformity, a crop of crooked, forked trees, of very little commercial value, will result. Biology and Control of the White-Pine Weevil 7 In addition to the direct damage caused by weevil attack, there are other secondary injuries that are of considerable importance. One of these is snow breakage. The irregular, dense growth of weeviled trees holds the snow to a much greater degree than does the normal straight pine. An extreme example of combined weevil and snow injury was observed not far from the Cornell University campus, in a group of trees located in a hollow where heavy snows collect. These trees were broken beyond any hope of recovery, and were little more than sprawling shrubs, barely able to keep alive. HOST trees The eastern white pine {Pinus strohus) is the favorite host of the white- pine weevil. However, the insect sometimes attacks other species of pine and some species of spruce. Scotch pine {Pinus syhestris), pitch pine {Pinus rigida), and jack pine {Pinus Banksiana) are frequently attacked when growing in mixture with, or near, young white pines. Red pine {Pinus resinosa) is much more resistant but is occasionally injured. Norway spruce {Picea excelsa) is very susceptible and is second to white pine as a favored host of this insect. Other species that have been reported as somewhat susceptible are Japanese pine {Pinus densi- fiora) (Peirson, 1922), Himalayan cedar {Cedrus deodara) (Currie, 1905), red spruce {Picea rubra) (Hopkins, 19 11), balsam fir {Abies balsamea) (Packard, 1890), and eastern hemlock {Tsuga canadensis) (Packard, 1890). It is possible that some of these earlier records may have resulted from the confusion of other species of Pissodes with the white-pine weevil. Packard, in his writings, evidently confused several species of Pissodes, and, as his records of hemlock and balsam fir as host trees of the white- pine weevil have not been verified by recent workers, it is possible that these two species should not be included as host trees of this insect. Since white pine is not only the favorite host of the white-pine weevil but is also the most important of the susceptible species as a timber tree, the experiments in both New York and Minnesota have been confined almost entirely to the activities of the weevil on this tree. relation of injury to age and HEIGHT OF TREE The first attack of the white-pine weevil usually occurs when the trees are from five to seven years old and from two to three feet in height. The infestation is generally rather light during the first year or so, but it steadily increases, reaching the maximum when the trees are from twelve to eighteen years old. From then on, the infestation declines rapidly in intensity, and it practically ceases to be economically important when the trees are from twenty-five to thirty years old. The rate of infestation appears to be correlated with the rate of growth of the trees, as is shown later in this bulletin; but there seems to be also some connection between the height of the trees and weevil injury (figure 4). The weevil ordinarily ceases to work on the trees after they have reached a height of from twenty to thirty feet. No entirely satisfactory explanation of this has been offered. It has often been assumed that insects which work only on low trees are habitually low fliers, and that when a tree attains a certain height it is beyond their reach. This may be the true explanation ; but it is equally probable that the changing eco- Bulletin 449 2(>0 240 220 200 ^/80 %./40 120 ^100 80 60 40 20 /" /S / / / / / / 79/4 / / a'; VI / f \ y //9' f3 1 f \ \^ 7 / / 1910 30 40 50 60 70 60 Average height, in inches 90 100 Figure 4, increase of the intensity of weevil infestation with height growth, FROM I9IO to I915 This graph was constructed from data collected on a series of sapling plots on the Luther Forest Preserve. In 1910 thS trees on these plots averaged seven years of age, two years after weeviling began logical conditions which take place conjointly with the development of the stand, may offer a more adequate explanation. In this study it was impossible to follow through, from year to year, the development of the young white-pine stands that were examined. At the conclusion of the investigation, the trees on the plots had not yet passed beyond the period of greatest susceptibility, and therefore the curve represented in figure 4 is incomplete. This figure does, however, show that the rate of infestation increased rapidly during the period from 19 10 to 19 1 5, as the trees grew from two and one-half to seven feet in height. RELATION OF INJURY TO CROWN CLASS AND RATE OF GROWTH From the foregoing section it may be inferred that the weevil has a decided preference for trees of certain ages and heights. Observations have shown that even during the highly susceptible age the weevil shows a preference for certain trees. It seems to choose the most thrifty and rapidly growing trees in the stand. Biology and Control of the White-Pine Weevil In even-aged stands growing nomially, the most rapidly growing trees are in the dominant and co-dominant crown classes. The distribution, according to crown class, of trees weeviled in 1916, is shown in table i, wherein it is seen that the weevil injury is confined for the most part to these two classes. Although these data were collected from sample plots in New York, they are typical of the conditions existing in all localities where the white-pine weevil has been studied. TABLE I. Distribution of Trees Weeviled per Acre in 1916, According to Crown Class Plot no Average height growth in 1915 (inches) Number of trees weeviled in 191 6 in the several crown classes Domi- nant Co-domi- nant Inter- mediate Sup- pressed 2 20 20 22 24 15 15 14 18 14 15 • 16 128 176 176 192 112 528 240 384 160 144 192 48 64 48 0 0 64 32 96 0 0 16 16 0 0 0 0 0 0 0 0 0 0 0 -i 0 4 0 5 0 6 7 0 0 8 0 9 0 10 0 II 0 12 0 Average 17-5 221 33-5 15 0 The crown class of a tree is indicative of two things : first, it indicates the position and size of the crown, relative to other trees in the stand; and secondly, in even-aged stands it is an indication of the rate of growth. The plots used as a basis for table i were all located in even-aged pure stands of young white pine, in which the dominant trees were, for the most part, rapidly growing trees. The data prove, therefore, that the domi- nant rapidly growing trees are the ones most attractive to the weevil. However, since the dominant trees were also the most vigorous, there is nothing to show whether it was the superior height or the rapid growth of the trees which determined their susceptibility. It has been assumed by Peirson (1922) that the height of the tree is the more important factor. This hypothesis is in accord with Peirson 's assumption that the beetles probably fly to the terminal shoots of the pines, and, in flying over a stand, select the tallest trees. In the work on which this paper is based, however, no evidence has been found that the beetles reach the terminals by flying. If they creep up the trees from the ground — • and there is direct evidence that this does occur (pages 11-12) — it is difficult to see how superior height alone could be an attraction to the weevils. In the field observations in New York, nothing was found which would prove that the weevil prefers the tallest trees if those trees are not also the most rapidly growing trees in the stand. There was, on the other 16 Bulletin 449 hand, no small amount of evidence in proof of the contention that the weevil chooses the most rapidly j^rowing trees, irrespective of their height. In stands where the trees were of unequal ages and heights, the weevil chose for attack the younger and shorter trees whenever these were grow- ing more rapidly than the older and taller trees. Field observations as to this preference of the weevil were further supported by an experiment at Ithaca in which four saplings were inclosed in a large cage. One of the trees was shorter than the others but was growing more rapidly. Six pairs of weevils were introduced into this cage on May 3, 19 15, and left free to select the tree best suited to their needs. On the day following their introduction, four of the six females began ovipositing on the small, rapidly growing tree. No other tree in the cage was attacked during the entire season. From the evidence at hand, it would appear that, in deteraiining the trees suitable for weevil attack, rate of growth is more important than superior height. But, since rapid growth and superior height go together, the dominant trees in the stand are found to be the ones most often attacked. This habit of stunting the best trees causes more damage than the mere loss of so much height growth in the infested trees. It interferes with the normal development of the whole stand: for, by its reducing the height growth of the most vigorous trees, the natural process of thinning is retarded; backward trees, instead of being crowded out, overtake the leaders; the rate of gx^owth for the stand, as a whole, is reduced; and, unless artificial thinnings are made, stagnation is* likely to result. LIFE HISTORY AND HABITS ACTIVITIES OF THE OLD ADULTS In 19 1 5, the first adults were observed on April 26 and the next day they were -seen to be ovipositing. Because of seasonal variations from year to year and because of the variations between different latitudes, a description of the general condition of arboreal vegetation at the time of emergence of the weevils from hibernation gives a more reliable indication of the emergence time than does a date alone. At the time when the weevils first appeared in 1915, the pine buds had just begun to swell. Of the deciduous trees, only the cherries were beginning to put forth leaves. The American elms had begun to set fruit, and the shadbush and the aspens were in full bloom. The oaks and the hickories showed scarcely any sign of activity. The weevils, as soon as they appear, begin feeding on the buds of the white pine. It is usually the terminal cluster of the leading shoot that is thus attacked. The weevils chew holes in the buds, and sometimes make cavities of considerable size. This injury, in itself, is important; but it is overshadowed by the later and much more serious damage caused by the larvae. Sometimes, to vary their diet a little, the adults feed on the inner bark of the terminal shoot. There is still some question as to the manner in which the adult weevils reach the leading shoots of the trees. Peirson (1922) assumes that they fly over the young pines and alight on the tallest terminals. This assump- tion appears to be open to some question, inasmuch as the weevil has Biology and Control of the White-Pine Weevil ii seldom been observed in flight. (Jnly once in the course of these investiga- tions has it been observed on the wing. This one occasion was in mid- afternoon of a warm day in the early spring of 1916. On that day, many weevils were fl>^ng. They were strong fliers, and when in the air their movements were similar to those of such bark beetles as Hylurgops. This unusual occurrence suggests the possibility of a short period of flight during earlv spring, whereby the weevil becomes widely disseminated, followed by a period when it seldom if ever takes wing. Figure 5. adult white-pine weevil During the spring of 1916 an experiment was conducted to determine, if possible, how the adult weevils reach the leading terminal. Two bands of tree tanglefoot, one just above the ground and the other at the base of the leading shoot, were placed around the stems of forty trees in a stand of young white pine that had been heavily infested by the weevil in 19 15. These bands were applied just before the adults began to emerge from hibernation. As soon as the weevils began to emerge, about two hundred were collected and liberated on the ground in the center of the plot. This number of weevils, added to the nurnber already present, insured a heavy infestation. With this arrangement of tanglefoot bands, it was certain that any weevils found on the terminal of a banded tree had not crawled up the tree. Any that were caught in the upper band must have alighted on a side branch, and any that were caught in or found below the lower band must have crawled up from the ground. During the entire season, no weevils were caught in any of the bands. Many weevils, however, were 12 Bulletin 449 found collected below the lower bands. Apparently they were attempting to crawl up the trunks in order to reach the terminals. Up to June 15, none of the banded trees were infested. By July 21, however, three weeviled shoots were found on the plot. It is possible that the weevils may have flown to the tips; but it is more likely that, during a cold rainy period in the latter part of June, the tanglefoot may have become glazed sufficiently to permit its being crossed by the weevils. Of the thirty unbanded trees on this plot, eleven were weeviled — an unusually large proportion for a single season. From this ex- periment it appears probable that, although the white-pine weevil is, under certain con- ditions, a good flier, it usually reaches the terminal shoot by creeping up the trvnik of the tree. In the spring, after having fed on the trees for a day or two, the beetles mate. During the entire oviposition period they are usually found in pairs, a male nearly always being found wherever a female is ovipositing. It appears, however, that they occasionally mate in the autumn previous to the period of ovi- position. The possibility of this was first indicated by an occurrence in one of the experimental cages placed over uninfested white-pine saplings near Ithaca. In the spring, before any weevils had been introduced, a female appeared, presumably from the litter at the base of the trees, and promptly began to oviposit. She laid 115 eggs in one shoot and did not move to any other during the entire period. The eggs proved fertile and nearly all of them hatched. No other weevil was in the cage during any part of the season ; therefore, the only possible explanation is that either the weevils can reproduce parthe- nogenetically, or fertilization in this instance had taken place during the preceding year. The latter supposition seems, on the face of it, the more probable. Further evidence on this point is presented later in this paper. After the brief period of feeding and mating, the females enter upon the task of oviposition. In ovipositing, the female makes with her beak a cavity in the bark of the terminal shoot, and excavates in the inner bark a chamber somewhat larger than the eggs she intends to lay. After carefully digging out and smoothing off the interior of this chamber, she turns around and feels about with her ovipositor until she finds the opening she has made. She deposits one, two, or occasionally three, of her small, pearly white, translucent eggs in the chamber. The operation of pre- paring the chamber and depositing the egg or eggs in it, often requires a half hour or more. The weevils continue ovipositing until sometime Figure 6. eggs and young larvae of the white-pine WEEVIL Biology and Control of the White-Pine Weevil 13 in early July. The latest that oviposition has been observed in New York was on July 6. Eggs laid after July i are so few as to be a negligible quantity. developmental stages After a short period, which, depending on the temperature, varies from six to fourteen days, the eggs hatch and the tiny larvae burrow downward, first in the inner bark and then between the wood and the bark. They eat out all the soft inner bark and cambium as they advance. Many of these small larvae are smothered in the resin which is exuded by the tissues of the tree. The larva that works ahead of his brothers is at a distinct disadvantage, and is usually overwhelmed by resin and killed. Figure 7. larvae of the white-pine weevil, almost full- grown This illustrates how the larvae work side by side down the shoot When, however, the larvae work in close formation, they kill the tissues of the tree so quickly that little resin is exuded. As a result of this, the larvae usually form a ring entirely around the stem and work downward, side by side. When a larva that is a little older than his companions attains full size, he drops out of the line, burrows into the pith, turns upward, and forms a pupal cell. The remaining larvae work down the stem until each is fully groum. Sometimes, as has been mentioned previously, they pass below the second, or even the third, whorl of branches, thus making the total length of a single tunnel from eight to thirty inches. Occasionally, when they are crowded at a whorl, some of the larvae may work up the laterals and form in them their pupal cells. Frequently one finds more larvae attaining full growth at a given point than can be accommodated in the pith, and then the pupal chambers are formed in the solid wood or between the bark and the wood. 14 Bulletin 449 The pupal chambers made in the pith or the wood are merely cells hollowed out of the tissues, without any lining whatever. Those made beneath the bark, however, are of a different type. A hollow is made in the wood, and this is arched over with shreds of wood matted together, forming the chip cocoon which is described by Packard in his fifth report. In none of the infested shoots that have been cut open and examined '^«'^* Figure 8. larvae and pupae of the white-pine weevil in their pupal cells Figure 9. larval tunnels of THE PINE WEEVIL (and these nimiber several thousand) has any lining been observed in the pupal chambers. Even those chambers that are roofed over with the chip cocoon have no lining on the side toward the wood. The larva may remain in the pupal cell for two weeks before trans- forming to the pupal stage. This stage lasts about twelve days, when the transformation to the adult occurs. In 19 15 the first pupae were observed on June 17, in shoots collected on May 9. If twelve days are added for the pupal period, fifty-one days were required from egg to adult under Biology and Control of the White-Pine Weevil IS conditions existing at Ithaca during the summer of 19 15. This length of time would vary somewhat from season to season, since the length of the developmental period is influenced greatly by weather conditions. ACTIVITIES OF THE YOUNG ADULTS After the beetles transform, they remain in the pupal cells for a period of from two weeks to a month. Final!}- they gnaw their way to the outside. Emergence of the young adults continues from the middle of July through September and into October. After they emerge, the weevils feed for a short time on the newly formed buds or the young growth of pines. After this feeding period they seek a place in which to hibernate dur- ing the winter, although the weather at the time may still be warm. Mention has already been made of an instance in which mating probably took place in the fall before hibernation. In order to determine whether or not this is possible, more than a hundred newly emerged weevils were placed in a cage in the laboratory on August 3. They were fed on fresh pine tips, which they ate voraciously at first. After a few days they be- came restless and began wander- ing around as if looking for a place in which to hibernate, but, since there was no litter in the cage, they were forced to keep in sight. They were kept in cages under observation until the last one died, in November. During this period but one pair copu- lated, and they only once. This indicates that occasionally the weevils may mate during the fall in which they emerge, but that such mating is rare. Hopkins (191 1) states that when the female weevils emerge their ovaries are undeveloped and they could not possibly produce eggs in less than a month after appearing as adults. If they laid eggs so late in the season as this would necessitate, the larvae would not be half grown by cold weather and could be found in the shoots during the winter. Never have living eggs, larvae, or pupae been found during the winter, although hundreds of infested shoots have been examined. One larv^a and one pupa, both in the pupal chamber, were found in the winter of 1914-15, but they were Figure 10. WHITE-PINE WEEVIL ON A NEW SHOOT 1 6 Bulletin 449 both dead. Apparently they could not survive the cold weather. The larva of the parasite Eurotoma pissodis Gir. winters in the pupal cell of its host, and the confusion of this parasitic larva with the weevil may account for the statement repeatedly found in literature, that the weevil may pass the winter as a larva. It seems possible that not all the adult weevils on the trees in mid- summer are adults that matured the preceding season. Possibly the beetles may live for two or three years and deposit eggs each year. From recorded observations of other species of the genus Pissodes in Europe and the United States, this fact has been definitely established (Hopkins, 191 1). If this holds true for the white-pine weevil as well as for other species of the genus, then, if every iminature individual should be wiped out of existence for one year or possibly two years in succession, there might still be enough adults the third year to reproduce the species and give it a fresh start. It may be due, in part, to its long life as adult, that the weevil is able to withstand the attacks of its enemies so well, winning out by persistence where other means might fail. During the winter of 19 14- 15 the weevil was sought in hibernation, but without success. The method used in this search was to sift onto a white oilcloth the trash and litter that was taken from beneath the pines, and examine it carefully. The failure to find the weevil in this way was due, doubtless, to its close resemblance to the bits of trash in which it was hidden. In November, 19 15, by the use of a modification of the Berlese trap, six adult weevils were found in the litter taken from under infested trees. On February i, more litter from beneath the infested pines was examined by the same method and five more weevils were found. Therefore the statement can no longer be questioned, that the beetles hibernate in the litter beneath the infested trees.^ A description of the trap, or extractor, used in finding these insects in hibernation, may be of interest. It consisted of an inverted cone, made of galvanized iron, with a one-inch opening at the bottom, where a detach- able glass bottle was fastened. This cone was surrounded by a water jacket one inch thick. The water was kept warm by the application of heat to a tank at one side, the dimensions of which were 8 by 6 by 2 inches. The tank was connected to the water jacket by a half-inch pipe at the bottom and another at the top, thus providing for the circulation of the water. The legs were of wood and were attached to the water jacket by riveted hinges, so that they might be folded against the cone. A screen was placed about two-thirds of the way down the cone so that the material under examination might not drop to the bottom and clog the opening. The cone was then filled with litter. In using this apparatus, the water in the jacket should be kept warm but not hot, so that the insects in the litter may be heated slowly. As soon as the insects become warm enough to come out of hibernation, they begin to work their way through the trash. Some burrow down- ward and fall into the bottle at the base of the cone. Others work their way upward and appear at the surface; these may be prevented from escap- ing by fastening a piece of cheesecloth over the top of the cone. So ' At the conclusion of this study of the life history of the white-pine weevil, it is eyident that, of all the earlier workers, Hoplfjns iigoi) has most accurately 4escrilpeci the life cycle. Biology and Control of the White-Pine Weevil 17 far, this apparatus has proved very useful in collecting all sorts of small and inconspicuous insects in hibernation which are easily overlooked in sifting litter. CONTROL The white-pine weevil, like other insects, can be controlled in several ways. The method to be selected depends on the conditions in each individual case. Control is largely an economic problem. The amount of labor and material used in these operations must be in proper propor- tion to the value of the trees protected. Naturally, the cost in all cases must be reduced to a minimum for the method used; but in some instances the value of the trees justifies the application of expensive control measures, whereas in other instances a comparatively low value of the trees will pennit the application of only the indirect or preventive type of control. For example, white pines used in ornamental plantings have a high esthetic value that cannot be measured in dollars and cents. On the other hand, a forest whose only purpose is the production of wood can never be valued at more than the market price of the stumpage. Between these two extremes there are all gradations. In the first instance, a large expenditure would be justified; but in the second, only a small amount of labor and material can profitably be spent. In a timber forest, even a small, injudicious expenditure in the early years of the rota- tion may consume entirely the profit which the timber might have pro- duced. In the following discussion of control, various methods are con- sidered and the conditions under which each is applicable are pointed out. Methods applicable in the control of the white-pine weevil may be divided into more or less arbitrary groups and subgroups, as follows: A. Direct control: Operations that deal directly with one or more stages of the insect, or with trees or parts of trees alread}^ infested. (Curative methods.) 1. Chemical methods : Sprays; washes; repellents. 2. Mechanical methods: Collecting adults- pruning shoots. B. Indirect control: Operations designed to modify environmental factors so that conditions become unfavorable for the rapid increase of the insect. (Preventive methods.) 1. Silvicultural methods : Shading; dense planting. 2. Biological methods: Parasites; predatory agents. These groups are taken up in their proper sequence. DIRECT CONTROL The direct methods of control are in their very nature rather expensive, and are therefore limited in application to trees that have some value in addition to the wood produced. Only under unusually favorable con- ditions will growth be sufficiently rapid and stumpage prices sufficiently high to justify the application of these control methods in a timber forest. Direct control is applicable to shade and ornamental trees in com- mercial nurseries, to windbreaks, along highways, on watersheds, and in some private forests where the esthetic value is an important consideration. It is to be expected that not all methods of control are equally effective. In order to justify their use under any circumstances, direct methods must i8 Bulletin 449 be highly efficient in checking or preventing weevil injury. They must surpass in efficiency the indirect methods in proportion to the increased expense, or their use cannot be justified. Chemical methods It is doubtful whether the chemical method of applying sprays or washes will prove sufficiently effective in controlling this pest to make its use economically practical. Britton and Walden (19 12), at the Con- necticut Agricultural Experiment Station, have conducted a series of experiments testing various materials. They found lime-sulfur, i to 8, to be an effective repellent under certain conditions. Experiments with this material at Ithaca failed to give satisfactory control. The results of insecticide tests conducted in the spring of 19 16 are sum- marized in table 2. No safe and effective spray or wash has as yet been developed, with the possible exception of a spray of creosote or carbolineum. TABLE 2. Chemic.\l Experiments in the Control of the White-Pine Weevil, 1916 Material Date of applica- tion Method of appli- cation Strength Chemical injury Number of trees treated Number of trees weeviled April 26 April 13 April 13 April 13 April 13 April 13 April 26 April 26 April 26 May 6 May 6 May 6 May 6 May 6 May 6 May 26 Painted Sprayed Painted Painted Sprayed Sprayed Sprayed Sprayed Sprayed Sprayed Sprayed Sprayed Sprayed Sprayed Sprayed Sprayed I to 3 I to 2 Pure Considerable .... None Trees badly in- 10 10 ID 10 10 10 10 10 10 10 10 10 10 ID 10 10 Creosote emulsion 3 Pure Growth stopped. Very slight None Pure 0 0 4lbs.to 100 gal. I to 8 1 to 25 3 lbs. to 50 gal. 2 lbs. to so gal. 5 lbs. to so gal. 10 lbs. to so gal. 1 to so 2 to so I to 3 None 8 Powdered lead arsenate None 3 2 None 2 Calite None 3 Calite Check trees Group no. Number of trees Number weeviled I 30 6 10 10 10 8 2 2 T. 3 5 4 4, 5 Mechanical methods Collecting adults In Connecticut, Walden (19 15) conducted a series of experiments to prove whether it is possible to control the white-pine weevil by collecting the adults during the period of oviposition. In those experiments a large net was held on one side of the terminal and a sharp blow was Biology and Control of the White-Pine Weevil ig administered on the other side, the beetles being thus knocked into the net. They were then removed from the net and killed. Undoubtedly an immense number of adult weevils can be captured in this way, but the question arises as to whether any appreciable impression on the numbers of the weevil can be made by this method in a badly infested plantation. Furthermore, the expense is too great for use in commercial plantations, since it costs from $1.50 to $2 per acre to make six collections. Felt (1906) also recommends this method of weevil control, and Peirson (1922) obtained satisfactory results by collecting adults in this way. A method employed on the Clark estate near Cooperstown, New York, has combined the collecting of adults with the cutting and burning of the infested shoots. There are on this estate about sixty-five acres of white pines, which were planted in 19 10. These trees were attacked when they were smaller than is ordinarily the case. At the time of the first attack, in 19 15, and for a number of years thereafter, a fight was waged against the weevil. Two boys were employed at $ i . 50 a day for practically three months of each year, barring rainy days. This made the cost of protection a little more than $3 per acre, which would be prohibitive on a strictly commercial plantation. However, it was the belief of the forester in charge that this method was effective. From experiments near Ithaca it was found that during the early part of the breeding season it was impossible to collect more than 75 per cent of the weevils by the net method, and at this time oviposition was going on at a most rapid rate. Small, badly infested plots were selected and were gone over with the net and stick. At this time the terminal cluster of buds had not separated. The weevils hide in the terminal bud cluster, and, when shaken, wedge themselves between the buds. Those that were resting on the stem could easily be knocked off into the net, but those hidden among the buds wedged themselves in so tightly that, in spite of the hardest shaking and knocking, they were not dislodged. After a plot had been covered with the net, each shoot was examined very care- fully, and in every plot a considerable number of weevils were found hidden among the buds. In one case there were more weevils left in these bud clusters than were caught in the net. Undoubtedly a number of weevils, when shaken off, missed the net and afterward found their way back to another terminal. After the bud cluster had separated, however, exceedingly good results were obtained by this method. It was impossible to tell just what percentage of the weevils were captured, but, judging from the small number to be found in the plots a day after the collecting, the proportion caught was high. From this it would appear that during the first of the season, collecting with a net is of little value though after the separation of the bud clusters it is satisfactory so far as the number of insects caught is concerned; but unless it is used in combination with some other method, such as pruning the weeviled shoots, its efficiency is doubtful. Pruning shoots The most practical and economical of the mechanical methods brought to the writer's attention, seems to be that of removing and destroying infested shoots before the emergence of the weevils. Even this method is too expensive and uncertain for general use in timber plantations. How- 20 Bulletin 449 ever, the practice has been advised by almost all the investigators who have studied the white-pine weevil, and, although it is rather expensive, it is reasonably effective if the work is done carefully and on a sufficiently extensive scale. The best time for such pruning, if it is possible to go over the plantation only once during the season, is the first half of the month of July. At this time practically all of the infested shoots have begun at least to wilt, and most of them have turned brown. They are then very conspicuous. The work can be carried on rapidly in a planta- tion where the trees are set out regularly. In irregular natural reproduc- tion, it goes forward much more slowly and is correspondingly more expensive. If possible, it is better to remove the infested leaders twice during the year: once in the month of June, and again in August. Before July few of the weevils will have worked below the first whorl of branches; and if the shoots are removed before that time, the leader will come from this whorl and a whole year of height growth will not be lost. Also, the laterals in this topmost whorl, because of their small diameter, are capable of straightening up much more easily than are the larger branches of the lower whorls. In July many larvae pass below the first whorl, and some- times by the end of that month, the second, and in a few cases the third, whorl has been passed. This results in a much more serious loss in height growth, and causes a crook that may never grow out. In June it is difficult to get all of the infested shoots, as some, in which the eggs have been recently laid, are rather inconspicuous; and so, in order to get those that have been missed, a second cleaning in August is advisable. The infested shoots should be removed every year as long as the weevils are in sufficient mmibers to endanger the final stand. This is especially true if the infestation is concentrated in spots, as is often the case. The weevils, as has already been mentioned, may perhaps live for as long as three years and deposit eggs each year. If this is the case, it will be necessary to prune for at least three years in succession, in order to sup- press an outbreak. If there are any other infested trees near by, they should be treated in order to reduce the number of weevils flying into the plantation from outside. By this method the weevil can be kept within reasonable limits. All infested shoots pruned from the trees should be disposed of in such a way as to make certain that the weevils do not get back to the trees. If a shoot is cut off and left lying on the ground, the weevils will go through their transformations and emerge just as if the shoot had been left on the tree. Therefore such shoots must be disposed of in some way. The method usually employed is that of burning the shoots. This certainly kills the weevils, but it also destroys the parasites and some of the predacious insects that prey upon the pest. Naturally the destruction of these beneficial forms of life is not to be desired. A much better plan is to place the infested shoots in receptacles tightly covered with wire mosquito netting. The wire netting should be no coarser than sixteen meshes to the inch. The weevils will be unable to escape, but most of the parasites can easily make their way through the meshes. Any tight receptacle will answ^er. It should not be stood upright, as in that position it would collect rain. The containers should not be opened, but should be left in the plantation until the following spring, when all the parasites will have emerged. By that time the weevils should all be dead, since the Biology and Control op the White-Pine Weevil 21 containers offer neither food nor a suitable place in which they could hibernate. Removal of the infested shoots suffices to keep the weevil in check, but it does not help the trees to recover from the attack. The laterals com- pete for the leadership, just as if the dead leader were still on the tree, and the characteristic forks and crooks result. If the trees are pruned in such a way as to favor one of these laterals as leader, they will be able to outgrow the weevil injury much more rapidly than would otherwise be the case. Experiments made in the course of the work show that, where the expenditure is possible, the pioming of all but one lateral in the top- most living whorl gives the best results. indirect control In commercial forests, where the value of the trees must be measured in terms of the wood produced, it is essential that the cost of controlling tree insects be kept at the minimum. This is particularly true during the early years of the rotation, when even a small injudicious expenditure means a considerable loss. It is under such conditions that one must rely almost entirely on the indirect methods of control. SilviculHiral methods It has been the observation of all who have made any study of the injury done by the white-pine weevil that this insect shows a decided preference for trees growing under certain conditions. If this holds consistently true, then one method of indirect control would be to secure for the growing of white pine those silvicultural conditions which are least con- ducive to weevil injury. In order to ascertain just what would be the best conditions to maintain, a series of experiments was carried on in New York and in Minnesota by means of sample plots laid out under as wide a variety of conditions as could be found. These sample plots were, for the most part, one-tenth acre in area, although in some cases they contained only one-sixteenth of an acre. In a few instances larger plots were used. By using small plots it was possible to so place them that conditions were fairly uniform throughout a plot, which with plots of larger size would have been difficult if not impossible. Practically all the plots were in stands resulting from natural reproduction. In these plots the relation of weevil injury to density, rate of growth, age, forest composition, and other factors, was studied with the object of determining what conditions would secure for white pine the greatest immunity from the weevil. The purpose of the experiments was to obtain data sufficiently conclusive to warrant the recommendation of certain definite silvicultural methods that would eliminate, or at least materially reduce, the weevil injury. This aim has been attained; and the coiTect- ness of the conclusions drawn from the data collected in this phase of the work have been verified by later investigators. It has already been noted that under certain conditions the weevil is particularly abundant — for example, on young trees from five to twenty years old, and trees that are growing unusually rapidly. These two conditions are not of particular interest in the control phase of the work, 22 Bulletin 449 because their very nature precludes their being changed. It is obvious that all trees must pass thrcjugh the susceptible age before being marketed, and that rapid growth is in itself a commercial asset. These investigations have, however, brought to light other silvicultural conditions favorable to the weevil, which can be so changed as to reduce the amount of injury, in some cases even to the point of almost complete elimination. Shading All students of the white-pine weevil have noticed the insect's preference for trees exposed to the sunlight, and the present experiments have con- firmed this observation. Weevil injury is invariably greatest in open pure stands of white pine growing in full sunlight. In mixed stands where hardwoods shade the pine, the injury is much less, and it decreases with increasing intensity of shade until it reaches the zero point under a shade such as that cast by an average stand of oak or maple. In view of these facts, which have been proved beyond a doubt, it would seem that some system of silviculture should be used which would pro- vide shade during the susceptible period: that is, until the trees are about fifteen to twenty-five years of age or somewhere between twenty and thirty feet in height. The density of shade tolerated by white pine will vary with soil and moisture conditions, and therefore must be determined separately for each site. On the better soils in New York, and to a lesser degree in the Lake States, white pine reproduces itself well under the shade of mixed pine and hardwoods. It would, however, be necessary to liberate the young pines by means of thinning, in order to prevent their succumbing to the competition of the overtopping trees. On poorer soils it would be difficult, if not impossible, to grow pines under hardwoods. Peirson (1922), as a result of experiments conducted in Massachusetts, also advises the growth of white pine in mixture with hardwoods in such a way that the pine will be slightly overtopped until it has reached the age of about fifteen years. In view of the fact that his experiments were carried on without knowledge of the work done around Ithaca or in Minnesota, it would appear that shading has received double recom- mendation as a silvicultural method of control. Dense planting The question next arises as to whether it is possible to protect pine from the weevil where shading is not feasible, such as in pure stands of volunteer young pine in old pastures, and in white-pine plantations. The answer to this question was found in data gathered from the sample plots of experiments regarding the influence on weevil injury of density of stand. From these experiments it appeared that in open stands where the crowns are all free, the trees are all equally subject to attack, but in the denser stands the percentage of trees that are attractive to the weevil is much less. In very dense stands the injury caused by this insect may be reduced to almost nothing. The effect of the original density of the stand upon its susceptibility to weevil attack is illustrated in figure 1 1 . The curve indicating the per- centage of trees that show the effect of weevil injury at thirty years is a summary of data collected in Minnesota, and represents an average of all plots where the original density could be determined with reasonable Biology and Control of the White-Pine Weevil 23 accuracy. The other curves in the fip^ure are from data collected on the Luther Forest Preserve in New York State. From these curves it is evident that the percentage of trees attacked by the weevil decreases with an increase of density. But, important as 4000 5750 5500 5250 5000 2760 2500 ^ 2260 l „ h'.»l ^Ail^Mll .M',^kM tl>^ r;— T— "^'~'' "^ '■ ' I '■!'i'"'"^' ;;| , ,'' ' » j * a, ¥' ■ f ;;t,i ^ "* .ilvi k if|!'*ij PLATE II. WORK OF SPRUCE, FIR, AND PINE INSECTS. A. Cross section of spruce showing ring retardation, due to defoliation, on tree that has recovered from Budworm. B. Ring retardation on tree that has not recovered. C. Egg tunnels of Pityokteinex sparsus in fir. (Slightly enlarged). D. Tunnels of Ips perturbaUis in white spruce. (J natural size). E. Tunnels of Ips pini in white pine. (^ natural size). F. Egg tunnel and larval mines of Dendroclonus piceaperda in spruce. G. Tunnels of Ambrosia Beetles in wood of spruce. 11 been reported from Maine, Vermont, New Hampshire, New York, New Jersey, Minnesota, Nova Scotia, Prince Edward Island, New Brunswick, Quebec, Ontario, and British Columbia. NATURE OF DAMAGE The spruce budworm is a defohating insect which starts feeding in the spring within the new buds of the fir or spruce, hollowing them out. The larva then con- structs a protecting shelter for itself by loosely binding together needles that have been bitten off. It later starts feeding on the foliage itself rapidly stripping the trees. Those trees that are completely stripped are usually killed outright. This is due in the first place to the interference with the normal functioning of the vital organs of the tree, — the lack of foliage bringing about the rapid drying out or death of the root hairs thru which water and essential minerals are absorbed, thus shutting off the food supply of the tree. In the second place conifers, unlike hardwoods, store up com- paratively little reserve food so that there is nothing to fall back upon. This is the reason why hardwoods may be defoliated several seasons in succession and still survive, whereas a single defoUation usually kills a conifer. Retarded Growth Particularly in the hardwood and mixed softwood- hardwood type where the spruce and fir have not been severely defoliated the growth is often retarded. Much valuable data was collected throughout the State in regard to dates in which the different areas were swept by the budworm, by making a study of the ring growth. Following defoliation the annual growth is greatly re- duced, so that it is possible to make an accurate estimate as to date of outbreak by cutting into green trees and counting the rings back to the point where retardation started. To obtain accurate results the count must be 12 made near the top of the tree. The first year's feeding is scarcely shown in that year's growth, as much of this ring is made up from food stored the previous year. The second year there is a decided reduction, so that the age of the outbreak is found by adding one to the number of rings between the inner bark and the ring in which decided retardation shows. A few rings may show an increase in growth during the second and succeeding years after feeding stops. Near the base of the tree, the retarded growth may not show up until four or five years after the first feeding. Death from Secondary Causes Large numbers of trees which have been only partially defoliated are so weakened that secondary enemies easily destroy them. It is, of course, the suppressed or over-mature trees that go first, due to their naturally weak condition. The nature of this dying, which usually extends over a period of several years, has been likened "to a greatly accelerated natural thinning that takes place in the normal forest", correlated with this, it has been very apparent that trees growing on poor or shallow soils are more likely to succumb. Due to the extreme importance of these secondary agencies in bringing about the death of the trees it is well to consider them separately. 1. Winter Killing. Large numbers of defoliated trees succumb the winter following defoliation due to winter killing. It has been shown that the ability of plants to withstand freezing depends in large measure on the concentration of the cell sap. Depletion of foliage prevents the formation of stored food thus lowering the concentration of the cell sap and making the trees subject to freezing. 2. Drying. In sample plots taken throughout Maine it has been very apparent that many of the trees that were only partially defoliated were unable to live through a dry season such as that of 1921. This is due largely 13 to the fact that there is little or no reserve food stored up in the trees. An interesting incident occurred in this connection. Of two ornamental firs that had been severely defoliated, one which was kept watered recovered; while the other died. Death from drying is particularly noticeable on mountain tops and other localities where the soil is shallow and moisture drains off quickly. Schierbeck suggests that balsam growing in mixture with hardwoods is better able to recover from serious defoliation due to the protection from evaporation of the soil moisture afforded by the hardwoods. 3. Bark-beetles. Considerable loss is caused by the swarms of bark-beetles which come into these areas of weakened trees. It is a common belief that these beetles never attack green healthy trees. This is a complete fallacy. In the normal forest they live and breed largely in sickly trees or green windfalls. Under these conditions birds and parasites are able to hold the beetles in check. Large areas of weakened trees such as are found after a budworm outbreak form ideal feeding and breeding places for bark-beetles so that they are able to increase rapidly in numbers and assume epidemic form. It is at this time that green trees are attacked and very often killed. Ordinarily the outflow of sap or resin brought about by the feeding of the bark-beetles drowns them, thus preventing their increase in green trees. It can readily be seen, however, that any great outflow of sap such as is caused by the attack of myriads of the beetles will so weaken the trees that they will become suitable breeding and feeding places. This is exactly what takes place during a bark-beetle epidemic and the trees are killed just as surely as if they were felled, the galleries made by the bark-beetles cutting off the flow of sap. 4. Fungi. Fungus diseases, particularly the shoestring root rot caused by Armillaria mellea, account for the death of large numbers of weakened trees. This fungus affects the bark and wood of the roots and destroys the living tissues. The decay very commonly extends up 3 14 into the bark and sapwood of the lower part of the trunk. Large amounts of resin commonly exude from the base of effected trees, accumulating as hard cakes. The fungus gets its name from the black strands resembling shoestrings which can be found attached to bark at the base of the tree and running thru the soil. The thin white sheets of mycelium spread out thru the cambium destroying the tissue. The fruiting bodies appear on the sides of the trunk or on exposed roots as clumps of honey-colored mushrooms. Large numbers of sample plots taken by Craighead in Canada showed that over seventy-five per cent of the dying balsams had one or more roots affected by this disease. In Maine a very similar condition prevails, the disease being common throughout the State. 5. Excess fruiting. Following severe defoliation fir, in particular, seeds very heavily. This takes a great deal of strength from the tree at a time when the little re- serve food present in the tree might do much to start it on the road to recovery. The trees apparently follow some natural law which causes them to bear a heavy crop of fruit when under adverse conditions in order to insure the continuity of the species. FOOD PLANTS The name spruce budworm has been very deceiving for the principal food of the budworm is the balsam fir {Abies balsamea). Counts made on hundreds of thousands of trees in Maine show that the relation between dead spruce and dead fir is seldom greater than two to three. In other words it is rarely over wide areas that more than two dead spruce will be found for every three dead fir. The first year's feeding during an epidemic is almost entirely on fir and it is only when the fohage from this tree is largely gone that spruce is attacked. Of the three species of spruce attacked red spruce is by all means the most severely injured. Black spruce is killed 15 to some extent when growing in mixture with fir. White spruce is rarely killed due to the fact that only the current year's foliage is suitable as food. In Maine this species is usually found in favorable growing conditions, particu- larly in abandoned pastures and is, as a rule, relatively hardy. In New Brunswick Craighead reports considerable damage to slow growing white spruce, particularly trees having low vitality. At times hemlock, larch, and white pine are attacked but these are seldom killed. The most severe damage usually occurs in localities where the caterpillars have either dropped onto these trees from spruce and fir or else have been blown on to them. The following is a list of known food plants: Pinus sirpbus Lamb . . . White Pine. Larix laricina (Du Roi) Koch . American Larch. Picea mariana (Mill) B., S. & P. Black Spruce. Picea rubra Dietre . . . Red Spruce. Picea canadensis (Mill) B., S. & P. White Spruce. Picea Abies (L) Karst . . Norway Spruce. Tsuga canadensis (L) Can. . . Hemlock. Abies balsamea (L) Mill. . . Balsam Fir. SEASONAL HISTORY AND HABITS It is w^ell worth while to review in a few words an active outbreak. In the first place observation has shown that the budworm is present at all times in the spruce and fir stands of northern Maine. It is, however, present in such small numbers that little or no attention is attracted by its feeding, which under non-epidemic conditions is limited almost entirely to the tips of fir receiving an abundance of sunlight. When conditions become favorable, the budworm again finding an abund- ance of food in the sunlight, such as young growth coming up in openings or older growth pushing up through the hardwoods, eggs are laid by the moths on the needles 16 at the tops of the fir trees that are in the siinUght. These eggs, which are laid from the first to the fifteenth of July, hatch in about ten days and the small caterpillars crawl into crevices in the bark, beneath lichens, or even into the cones, where they spin a small cocoon and thus pass the winter. They come out in the spring just before the balsam buds open and feed for three weeks or more on the foliage. An abundance of food and a favor- able season mean that most of the caterpillars will mature and later turn into moths which again lay large numbers of eggs. Thus it is that an epidemic starts. The moths in flying over the forest seek out and alight on the tops of fir trees. The first year's feeding is almost exclusively on fir, spruce being practically free from injury. The second season again finds the moths in flight. Some of them, however, remain and lay their eggs on the spruce. This accounts for the fact that the greatest injury is to the fir, and also emphasizes the fact that the intensity of an outbreak over wide areas depends largely upon the amount of fir that is present in a region. This habit of the moths seeking fir that is growing in the sunlight also accounts for the fact that spruce and fir found in mixture with hardwoods is less liable to damage from budworm attack than that growing in pure stands. It also accounts for the fact that spruce and fir coming up under the protection of hardwoods or budworm killed timber, is seldom damaged. Wind undoubtedly plays an important part in the spread of an epidemic. It has been possible to trace the movement of the series of outbreaks occurring during the last ten years by a study of ring retardation in trees that have recovered from budworm injury. Notes were taken throughout the Maine Forestry District and dates of outbreaks plotted on a map. It is quite apparent that as a rule the outbreaks follow the valleys, spreading up on to the ridges. In some sections of the State the spread of the moths was north, in other sections south, depending apparently on the direction of the prevailing PLATE III. SPRUCE AND FIR INSECTS. A Fir tip on which feeding has started. B. Egg mass of Budvvorm on fir needle (greatly enlarged). C. Larva of Budworm. (Enlarged U x). D. Pupa of Bud- worm. (Enlarged U x). E. Moth of Budworm. (Enlarged U x). F Typical barkbeetle tunnel beneath bark, showmg large adult tunnel and small larval tun- nels (Natural size). G Parasitic Hymenoptera laymg egg in wood boring larvae. (Natural size). 18 winds during the period of flight. The moths are fre- quently blown on to high mountain tops where the spruce and fir are severely damaged. Many reasons have been given for the somewhat periodic appearance of wide-spread outbreaks in the past, but few of these take into account the fact that during an active outbreak the caterpillars are present in such vast numbers and over such a great territory that it is utterly inconceivable that either birds or parasites could check their advance. The one great factor is lack of suitable food. When the majority of the fir has been defoliated the outbreak soon dwindles down. DESCRIPTION OF STAGES The Moth The moth is robust with a wing expanse of slightly less than one inch. The fore wings which are approximately one-half inch in length, are large, broad, and oblong in shape. In color the fore wings are umber brown, the brown sometimes being replaced by a rust red. The ground color of the wing is a bluish slate. There are numerous fine, transverse, short brown lines which divide the wing into checks or squares. Numerous brown spots and patches occur on the wings and near the middle of the wing is a broad brown band crossing it in a zig zag fashion. The umber brown markings which show con- siderable variation are sometimes replaced by a bright rust red color and the clay-blue by a ferruginous brown. The legs, body, and hind wings are of a glistening umber brown. The length of the body is approximately one- half inch, and in the female is very stout. That of the male ends in a long distinct hairy tuft. The Egg The egg is pale green, broad, oval, scale-like, flat beneath and slightly convex above. The shell is thin. The egg is about one-sixteenth inch in diameter. The 19 eggs are laid in shingle-like patches over-lapping each other irregularly. These patches may be composed of as many as thirty eggs. The Larva When first hatched the larva is pale pea-green with a yellowish tinge. The head is dark brown. The mature larva is of a rich umber-brown color, diffused with olive green markings near the sutures or body segments. Very conspicuous yellowish-white warts occur along the sides. The head and fore legs are of a dark brown color. The full grown larva is approximately three-fourths inch in length. The Pupa The pupa is approximately one-half inch in length. The body is comparatively thick, tapering at both ends and is of a tan brown color. The antennae and legs are dark horn colored, the wings pale with dark veins, the thorax spotted and with three irregular, dark stripes, abdomen with two rows of stout spines above, and a lateral row of dark spots. NATURAL ENEMIES It is unquestionably true that birds and parasites play an important role in holding in check the budworm and subsequent outbreaks of bark-beetles. These, how- ever, cannot be depended upon to prevent epidemics. Several very interesting incidents of the work of both parasites and birds are on record. It is claimed that the budworm gained unusual headway during seasons when the smoke from forest fires drove the birds out of the forests. Several observations show that spiders destroy large numbers of the young larvae. Very interesting data were collected by the writer on the effects of heavy storms in holding in check incipient outbreaks of the budworm. The young larvae are 20 washed off from the boughs in large numbers and drowned, and during continued heavy showers an outbreak may be almost entirel^^ stamped out. CONTROL BY FOREST MANAGEMENT It is the purpose of this paper to emphasize the possi- bilities of controlling and preventing wide-spread out- breaks of the spruce budworm by means of forest manage- ment. Work has progressed far enough to prove that this can economically be done. It is essential, however, that plans be put into operation at once, for the time to fight an insect outbreak is immediately after it starts. The belief held by some that the danger from the bud- worm has passed is entirely groundless for new outbreaks are continually starting up. One of the most startling results showing up from the field work of the past season is the ever increasing amount of fir that is coming in to the forests. This only emphasies the need of putting control and preventive measures into effect immediately, if the remaining green stands of spruce are to be saved. The following methods of control are already being put into operation in Maine by the writer and if con- tinued and carried to completion should insure the timberlands of the State against future serious damage by the budworm. Already several outbreaks have been stamped out. (1) Forest Type Map It has been very apparent when studying spruce bud- worm outbreaks that the type of the forest growth is the controlling factor both as to determining where an out- break may start and the extent of the damage likely to be done. Sample plots taken throughout the spruce region in Maine have emphasized this point, as have plots taken by Craighead in the Provinces. Outbreaks start in pure softwood areas where fir makes up a high percentage of the stand. Once started the intesity of the 21 outbreak depends largely upon the percentage of spruce and fir in an area. Spruce and fir occurring in mixture with hardwoods receives a reasonably high degree of immunity due to the protection or shade of the hard- woods. In like manner small isolated bodies of spruce and fir very commonly escape injury. With these points in view a general forest type map of the entire forested region of the State is being made. Already over one-half of the Maine Forestry District has been typed and the remainder is rapidly being com- pleted. This work is being carried on largely by the Chief Forest Fire Wardens who are in most cases men who are very familiar with their territory. A great deal of help has been received from foresters, cruisers, and timberland owners. For the present only eight types are being considered. 1. Spruce and Fir. 5. Coniferous Swamp. 2. Northern Hardwoods. 6. Aspen or Poplar. 3. Mixed Softwoods and Hard- 7. White or Paper woods. Birch. 4. White Pine. 8. Gray Birch. The final type map will be of utmost importance in locating danger points and in planning control measures once an outbreak starts. (2) Patrol of Area The second phase of the problem of preventing future outbreaks takes the form of scouting and education. Fortunately the Maine Forestry District, in which the majority of the spruce and fir occurs, is fairly well pa- trolled by wardens, patrolmen, foresters, and timber cruisers. These men have, for the most part, been made acquainted with the nature of insect outbreaks thru talks and letters and have been requested to notify the office as soon as any are located. In this way the State already has several hundred men constantly on the lookout, and it is hoped to locate outbreaks long 22 before they reach serious proprotions. Budworm and bark-beetle outbreaks often show up from the fire lookout stations, for the reddening of the trees is visible for long distances. In connection with this part of the work the type map will show the areas which should be visited once a year and every effort will be made to have this done. Reports of outbreaks are carefully checked and if deemed advisable the area is visited by the entomolo- gist. (3) Control of Outbreak The third and final phase of the problem comes after the outbreak has been located and visited by the ento- mologist. If the infestation proves serious and gives promise of doing considerable damage, the infested area is marked on a map and the owner notified with the request that he plan his winter's operation, if possible, so as to clean cut the spruce and fir in this area. This request will not be made unless it is absolutely necessary in order to save the surrounding forest, and from the attitude shown so far by the land-owners it is believed that in the majority of cases the request will be granted. If the infestation is located in time it may not be neces- sary to operate in this region until the second year. This method of stamping out new infestations, which has already been tried with success, is based upon the fact that the budworm passes the winter as small larvae which have just emerged from the eggs and are so weak that unless suitable food is present when they emerge in the spring the caterpillars will soon die from starvation. Clean cutting the area in the winter means that when the larvae emerge in the spring there is nothing in the area but dry tops, the food supply of the insect having been destroyed. Under average conditions the necessary size of the cut will be comparatively small and could well be handled by a small jobber. The operation should, if properly planned, practically, if not entirely, pay for itself. The protection to the surrounding timber 23 would more than offset any financial loss due to the operation. In the case of owners who do not do their own operating, a small stumpage sale could be planned for the area. Improvement of Forest Crop Considerable progress can be made in improving the forest crop so that the likelihood of future wide-spread outbreaks will be much lessened. Serious insect epi- demics almost invariably occur in pure stands. In the present budworm outbreak the greatest amount of damage took place in the pure spruce and fir stands, the mixed soft and hardwood stands were far less seriously injured and it is questionable if any outbreak at all would have occurred if it had not been for the large areas of practically pure spruce and fir. In the future every effort should be made to cull out the fir from the forest and to favor a mixed spruce- hardwood forest. In order to bring this condition about it will probably be necessary to leave a certain number of spruce seed trees and possibly girdle some of the over mature hardwoods in case they are making up too high a percentage of the stand. In areas in which fir does make up a high percentage of the stand a short rotation should be adopted. In the mixed softwood- hardwood type emphasis should be laid upon the culling out of all fir and the cutting of the softwoods as soon as economically possible after they out-top the hardwoods wherever the softwoods make up a high percentage of the stand. In many areas it would be decidedly worth while to merely girdle all fir in the winter in case they cannot be cut and utilized at the time of the operation. SALVAGING OF BUDWORM KILLED TIMBER One of the greatest problems which the timberland owners in Maine have had to face has been the salvaging of the dead wood left as a result of the budworm epi- 24 demies during the last ten years. Many small owners have been practically bankrupted, being unable to harvest or sell their budworm killed timber due to the flooded condition of the market with this dead wood. Some of the large companies w^hich have been salvaging this insect-killed timber during the last five years already have from three to five years' supply cut. The length of time that the timber is worth salvaging, after having been killed by the budworm varies for both spruce and fir depending largely upon the growing conditions. In general, it has been found that for pulp purposes fir must be salvaged within three years from time of death, and spruce within five and in some cases seven years. Rots and wood-boring insects attack the trees the summer following defoliation by the budworm and soon ruin the wood for lumber purposes, so it is necessary to salvage wood for this use immediately. The fact that the wood wall not peel only adds to the difficulties and cost of salvage. Apparently the more rapid the growth of the spruce and fir the more rapid it deteriorates after death. This seems to be general throughout Maine. Spruce and fir growing in swamps or on extremely shallow ground, such as is found on rocky ridges or mountain tops, soon dry out due to the small amount of sap in the wood, whereas that growing on the more favorable sites contains a considerable amount of sap and remains favorable ground for insects and fungi much longer, besides being more suitable in the first place. Great savings could be made if these factors were taken into consideration when planning cutting operations. Unfortunately some operators are going at it in just the reverse manner, cutting the wood which will remain sound for the longest time first and leaving the wood which will rapidly deteriorate for future operations. The fact is that this is going to mean that much of the wood will never be salvaged that otherwise might have been. There is a strong reluctance on the part of many operators, and upon individuals as a whole, to face the real situation. The full effects of the budw^orm outbreak are yet to be felt. 25 BARK-BEETLES Several species of bark-beetles at times destroy large areas of spruce and fir. These small beetles bore through the outer bark and lay their small whitish eggs along tunnels made in the inner bark, from which minute whitish grubs hatch and start feeding in the cambium, finally girdling the tree. The attack first shows up on the trees in the nature of fine reddish, sawdust-hke borings deposited on the rough bark or lichens. The exuding of pitch mixed with the borings is also very common. The foliage of effected fir turns pale green, later taking on a yellowish and finally a reddish hue, the trees assuming a mahogany-like color. The bark finally loosens and is easily broken off. In the case of effected spruce the old growth needles do not turn color but drop off green leaving the tree with scanty foliage. EASTERN SPRUCE BEETLE Dendroctonus piceaperda is by all means the most in- jurious of the bark-beetles likely to kill spruce in Maine, and has in the past destroyed the red, black, and white spruce over wide areas. This is a reddish brown to black beetle approximately three-sixteenths inch in length. Its body is sparsely clothed with long hairs. The insect passes the winter in the inner bark. The beetles emerge from June to October, the majority coming out in July, and immediately attack trees excavating galleries. According to Hopkins, "The beetles enter the bark of healthy trees at a point from six to ten feet from the base, and that of weakened trees from near the base to the larger branches. In the living trees the entrance burrow is gradually extended obliquely upward, thence in a longitudinal direction upward through the inner bark, often grooving the surface of the wood. Along the sides of this gallery, which is usually about three times as broad as the beetle, the eggs are placed singly in small cavities or in groups in an elongated 26 cavity. The eggs are then protected by a mass of borings, closely packed and cemented with gum." As this gallery is being built numerous openings to the outside are excavated and then filled with borings as the gallery advances. SPRUCE BARK-BEETLE Polygraphus rufipennis is very abundant in the bark of dying spruce and may at times become of primary importance and attack green healthy trees. This beetle is stout, jet black, and slightly over one-sixteenth inch in length. BALSAM FIR BARK-BEETLE Pityokteines sparsus at times destroys large amounts of balsam fir in the Northeastern United States. This minute beetle, which is approximately one-sixteenth inch in length, is particularly active in destroying over-mature and weakened trees. SECONDARY BARK-BEETLES There are large numbers of species of bark-beetles which attack only weakened, over-mature, or dead trees. It is rarely that an injured conifer is not sooner or later attacked by these beetles, which do much to bring about the rapid death and deterioration of the trees by loosening the bark and allowing moisture to seep in. These beetles are admirably covered by Swaine in a paper entitled "Canadian Bark-Beetles". Control. In general it can be stated that if active measures are taken to stamp out and prevent epidemics of the budworm, the danger from bark-beetles will be materially lessened, as these almost invariably start up in areas of weakened trees. Outbreaks of bark-beetles are easily located by the scanty foliage or by the yellowing and then reddening of the foliage 27 on infested trees which shows up for long distances. These so-called "beetle trees" often occur in clumps. Outbreaks can usually be controlled without great difficulty as the habits of bark-beetles render them readily vulnerable by methods that lumbermen can economically employ. The removal and utilization, peehng, or burning of the infested trees is the most satisfactory control, and an infestation can be checked in a single season by destroying these "beetle-trees". Floating the logs in the early spring, as is the usual custom, also destroys the beetles. When only a portion of an infestation can be treated, control measures should be concentrated against the centers of infestation, cutting the trees and either floating them or else peeling off and burning the bark. These methods of control do not apply to the old "red tops" from which the primary bark-beetles have emerged. They do apply though to freshly infested trees on which the foliage may be scanty, green, yellowish, or of a slightly reddish tinge. As in the case of budworm control it is highly desirable that as complete a patrol as possible of the forest region be maintained in order to locate incipient outbreaks. There are two factors other than defoliation which may be the primary cause of bark-beetle outbreaks starting up. The first of these is a ground fire which scorches the base of the trees. The second is the accumulation of large amounts of green slash whether due to logging operations or windfall. Under certain conditions this accumulation of green slash may be a decided menace to the surrounding timber, not only due to the fact that it may serve as a breeding place for the beetles, but also due to the fact that such an area serves to attract large numbers of the beetles. Climatic conditions play an important role in in- fluencing the increase or decrease of bark-beetles. It has been found that the beetles breed most rapidly in warm weather w^hen there is a moderate supply of mois- ture, but that their increase is retarded by periods of cold' wet weather. The beetles are easily dried out by sunlight and wind striking the trunks of the brood trees. 28 WOOD BORERS Considerable damage is done to unpeeled long lumber and pulp by wood-boring insects which attack the wood during the summer months. In like manner trees that have been injured by fire are severely injured by these borers. There are two principal types attacking spruce and fir. ROUND-HEADED BORERS Four species of Monochamus are commonly found boring in spruce and fir. These are large beetles with long antennae from which they get the common name "long horned beetles". Eggs are laid during the warm months in the bark of trees or logs which are in the sunlight. These eggs hatch into white colored grubs which begin boring beneath the bark and later enter the sapwood making tunnels of about the size of a lead pencil. Monochamus scutellatus is black and approximately one inch in length with antennae of male about twice the length of the body. It is common in June and July. Monochamus notatus is brown and of approximately the same size as M. scutellatus. It is found in June and July. Monochamus titillator is a large brown mottled gray beetle with a body length of about one and one-half inches. It is most commonly found in the early fall. Monochamus marmorator is a mottled gray beetle of about the size of M. scutellatus. This species attacks both green and dying fir. The adult is found active in the evening. It is common in June and July. FLAT-HEADED BORERS There are numerous species of flat-headed borers be- longing to the family Buprestidae which cause consider- able damage to dying and cut timber or pulp. As in the 29 case of the round-headed borers these beetles lay their eggs in the bark. The larvae, which are elongate and somewhat flattened, start boring beneath the bark, later going into the sapwood. Control. Summer logging should be planned so that the logs are either peeled or else got out of the woods as rapidly as possible. Floating them will prevent injury. The round-headed borers attack principally logs lying in the sunlight so that some success has been obtained by keeping the logs in the shade. Craighead has made considerable headway in developing a cheap repellant spray which could be used on piled pulp or logs. The work, however, has not been completed. Dilutions of creosote oil containing up to eight parts of kerosene proved most effective. It is planned this summer to carry this work to completion in Maine. The normal loss from borers to piled unpeeled pulp amounts to nearly ten per cent the first year. The loss to logs cut for lumber purposes is much greater, and very commonly logs left lying in the open during the summer months are entirely ruined due to the worm holes. White Pine Insects INTRODUCTION The changes in composition which have taken place in our New England forests during the last one hundred years are portentous. White pine which at one time seldom occurred in pure stands of any size now occurs in large bodies throughout central New England. This means that what at one time was a mixed forest crop has now become a specialized crop. Insects which at one time had only individual trees of the same species scattered here and there through the forest to feed upon, now have large forests of the same species to satisfy their greed. This fact alone accounts for the great increase of certain obnoxious forest insects. We find a striking analogy in the agriculture of the country. As man specializes more and more, insects which at one time had only small individual plots of a given food to feed upon, now find this same food in great abundance over large areas. No one factor so influences the rise and fall in abundance of an insect pest as the food supply. The increase in abundance of white pine has hardly been able to keep up with the increased demand for it. From the earliest days of lumbering, the white pine has been the favorite tree in the North-east. In the great spruce regions of Maine 'it was the first tree to be cut and in these areas was so thoroughly culled out that it has not returned as a species of any importance in the new crop, the lumbermen falUng back first upon the spruce, then the fir. In central New England, however, the pine has seeded into the many abandoned pastures and at present forms the principal forest crop of this region. This so-called second growth white pine is by no means of as good 32 quality as that occurring in the original forest, but an ever increasing demand for this low grade pine has made it a tree of very great value. The realization that the pine will not last forever has resulted in large numbers of plantations of white pine being set out in an effort to keep the crop on a sustained yield basis. With the increase of the areas set out to white pine, has come a like increase in the prevalence of the insects attacking the pine. In some localities the apparent damage from insects has been so great that a decided damper has been put upon the interest in planting this species. This is decidedly unfortunate in view of the large program of reforestation which has so carefully been built up. It is highly important then to know in advance the extent to which existing planting plans and methods of manage- ment should be modified to meet these enemies. Enough white pine has been planted now in different localities throughout this region to make it reasonably safe to predict just what is to be expected in the way of insect damage. INSECTS ATTACKING SEEDLINGS WHITE GRUBS Practically all injury likely to result from insect attacks on the seedlings can be circumscribed by proper planting methods. First in importance and probably the most common injury is that resulting from white grubs (Phyllophaga) which are well known to most nurserymen and farmers. These grubs are in reality the young of June bugs. Normally they feed upon the roots of grass and it is seldom that they become a serious pest to the agriculturist except when grass land is turned over and planted. As this is a very common practice the grubs are consequently often a serious menace. The possible damage can usually be greatly minimized by cultural methods such as fall plowing or by planting the area to corn or clover the first year. Pasturing hogs 33 in the area is often resorted to. J. F. Illingsworth, an Australian entomologist, has recently obtained remarkable results by the use of crude white arsenic, applying eighty pounds per acre. This method of control is based upon the fact that in feeding a large amount of soil passes through the intestinal tract of the grub. By mixing the arsenic with the soil, when preparing the seed bed, almost perfect control may be expected. No detrimental effect upon plant growth was noticed even when the arsenic was used in excessive amounts. PALES WEEVIL It is practically useless to start a coniferous nursery on a white pine area that has just been cut or on a plot that is contiguous to such an area. The pales weevil, {Hylobius pales) which is a snout beetle, is attracted in large numbers to areas where freshly cut pine stumps, logs, boards, or even slash occur. These beetles are ravenous feeders, eating the tender bark off from pine seedlings and invariably proving a serious pest on such areas, often entirely destroying the nursery. It is not safe to plant in such an area until the third year after cutting. This statement also holds for planting of pine on cut-over pine lands during the first two years following the cutting. Such plantations are invariably a failure. The beetles breed in the fresh pine stumps and logs. The damage may be materially mitigated by burning the slash over the stumps and utilizing the logs in the early spring, but this will not entirely prevent injury. The age of seedlings killed ranges from one to five years. Year old seedhngs are seldom attacked, whereas those over five years of age are usually of sufficient size to overcome the damage. STRAWBERRY CROWN GIRDLER In 1915 the strawberry crown girdler (Brachijrhinus [Otiorrhynchus] ovatus L.) caused a loss of over $15,000 in one Massachusetts nursery to white pine seedlings. The PLATE V. WHITE PINE INSECTS. A. Leader killed by White Pine Weevil showing characteristic drooping of cur- rent year's growth, and pupal chambers with exit holes. (J natural size). B. Larva of Leconte's sawfly. C. Work of Pine Tube Moth. (i natural size). D. Adult Pales Weevil. (Enlarged 2 x). E. Work of Pales Weevil on pine seedling, showing girdling effect. (I natural size). 35 larvae, or small white grubs, girdle the stems and the roots at from one to three inches below the surface of the ground. There is a large range of food plants in- cluding red and Scotch pine and several species of spruce. The larvae pupate in the ground during early June at a depth of from one and one-half to three inches and may be destroyed at this time by plowing and harrowing. The adults can be trapped under boards, weed piles, burlap, etc., particularly during hot dry weather. They are active only at night. The larvae live for from ten months to one year. Fortunately it is seldom that this insect proves troublesome. At times the seedlings may be attacked by foliage eating insects, but these are easily controlled by using a lead arsenate spray. INSECTS ATTACKING SAPLING PINE WHITE PINE WEEVIL Undoubtedly the most serious enemy of the white pine is the white pine weevil (Pissodes strobi), but exten- sive experiments carried on by the writer have shown that even the ravages of this destructive pest are easily overcome by proper forest management. This beetle lays its eggs in the terminal shoots of the white pine. These eggs hatch into small white grubs which imme- diately begin feeding just beneath the bark on the wood of the shoot. As the grubs increase in size they feed deeper into the wood, all of the time working downwards. Needless to say the leader is soon girdled and immediately begins to wither up and die. Often the grubs will con- tinue feeding in the main stem until they have passed the first, and at times even the second and third, whorl of laterals. The results of this destruction of the main shoot are three fold. In the first place it results in crooked, forked, many branched trees. Secondly it materially lengthens the time of rotation for the crop. In the third place injured trees are very apt to have large knots U O e CO •Si > ■S 00 ^">> c-6 U o o Z e c3 P ■ a a > << , , nooc 5 ° J3 O 'c pc 37 and short internodes which lower the grade and value of the lumber. The method of control is based upon the fact that in a reasonably dense stand the trees do not have the opportunity to fork and branch out. The natural closing in of the stand does not allow room for more than one terminal shoot, and any others are soon crowded and shaded out. If then a stand of young pine can be started with a density of from 1200 to 2000 trees per acre, on reasonably good pine soil, the trees, although badly weeviled, will overcome the injury. As the majority of white pine plantations are set out using a six by six foot spacing, or 1210 trees per acre, the resulting stand will be of good quality in so far as lack of weevil injury is concerned. Much of the very serious damage resulting from weevil injury in plantations is due to poor planting methods. The weevil attacks trees between the height of two and one-half and fifteen feet, seldom doing great damage above this height. It is patent then that the sooner the trees reach this height the less damaged they will be, for the trees may be attacked by the weevil each year. Trees planted on poor soil such as sandy ridges or swamp lands are naturally slow growing and may be weeviled ten or fifteen times before they even reach a height of ten feet. The internodes, or distances between the whorls of branches, are so short that in order to mature the grubs may destroy several years' growth during a single season. Such trees are almost invariably knott^^ and crooked regardless of the density of the stand. Poor stock used in planting or careless planting methods which result in a number of the trees dying leaving open spaces in the stand, allow the weeviled trees to fork and branch out. Such spaces should be replanted. On the average quality II site the mature stand of from fifty to sixty years should contain from 250 to 300 trees per acre. MOUND BUILDING ANTS Another insect of considerable importance which attacks sapling pine is the mound building ant, (Formica 38 exsectoides). These ants destroy all the vegetation around their nests for distances up to a twenty foot radius and kill young pine trees until they reach a height of six feet. The ants use a unique method in killing the trees. Formic PLATE VII. Mounds of Formica exsectoides showing barren area around them. acid is injected by them into the tissues of the main stem a short distance above the ground. The acid coagulates the cell contents, thus preventing the downward flow of the sap. The lesion appears superficially like a fungus canker. It is useless to plant pine within fifteen feet of these mounds, which are often three feet in height and six or more feet in diameter. These ant colonies are not easily destroyed as the queens, or mothers, live deep down in the nest often five or six feet below the surface of the ground, and unless these are killed the colony will continue to live. The use of carbon bisulfide has, however, proved very satisfactory in destroying the colonies. From one to one and one-half pounds of the bisulfide should be poured into a shallow dish which is then placed on top of the nest. A few holes should then be punched in the mound with a stick and a large pan inverted over the nest in order to prevent the fumes from escaping. A little fresh earth or a few sods thrown around the base of the ^9 pan will aid materially in keeping the gas within the nest. Carbon bisulfide is sold on the market in liquid form. On exposure to the air the liquid soon volatilizes to a gas of disagreeable odor. This gas, which is 2.68 times as heavy as air, penetrates deep into the recesses of the nest, killing the ants. The smaller the nests, the less bisulfide is necessary, and the easier it is to destroy the colony. WHITE PINE APHID Often times large colonies of black aphids, or plant lice, are found on the needles and small twigs of pine. These are commonly known as the white pine aphid (Lachnus strobi) and are often the cause of the browning of the needles and the final death of the trees. These little plant lice occurring as they do in large numbers take an immense amount of vitality from the trees attacked. They increase in numbers very rapidly during the year, there being several generations during the season, so that the resulting off-spring from a single female is enormous, it being estimated at one billion as the least possible number if all should live. Fortunately these aphids are very frail, weak-bodied insects and are destroyed in large numbers by rains, and other agencies. It is ciuite common to find them in company with the m^ound building ants. In planta- tions they may be destroyed by spraying the trees with 40 per cent nicotine sulfate, used at a dilution of 1 part nicotine to 800 parts of water. It is seldom that large trees are damaged and even in the plantations they usually occur only on individual trees so that it is seldom necessary to spray extensively. GIPSY MOTH A large plantation of white pine in southern Maine was attacked this last summer by first stage gipsy moth larvae {Porthetria dispar) and would have been entirely 40 destroyed had it not been immediately sprayed. The caterpillars, which had been blown in great numbers on to the plantation from surrounding birches, were feeding on the epidermis of the main stem and laterals of the young pine, entirely girdling them. The small brown caterpillars are covered with both long and short hairs which aid materially in making them buoyant. The spinning of a long thread, as is the case with spiders, adds to their buoyancy. Records taken by Collins show that the larvae may be blown for several miles. The feeding of the larvae on the epidermis of the stems of seedhngs is, however, unusual. The plantation was sprayed with hand sprayers using arsenate of lead at the rate of three pounds to fifty gallons of water. The more mature stages of the gipsy moth larvae feed to a considerable extent on the foliage of the white pine. PINE TUBE MOTH An interesting and rather unusual insect outbreak occurred this last summer in a large white pine plantation in New Haven, Conn. The insect causing the damage was the pine tube moth (Eulia pinaiubana) which is quite common in Maine, but rarely causes any serious damage. In the fall the pale green larvae gather a bundle of about fifteen needles together into a tube within which the caterpillar lives, feeding on the ends of the needles. In October 1922, when the above plantation was visited, the tops of a large number of the trees had been entirely defoliated. Fall spraying is the only known method of controlling an outbreak, but fortunately this is seldom necessary. MISCELLANEOUS SPECIES There are several other insects, usually of minor importance, which attack sapling pines. These should be mentioned, although it is seldom that they will be found in large numbers. First in importance are the 41 larvae of saw-flies. Superficially these look like hairless caterpillars and are usually of a uniform color, either yellow or green, feeding entirely upon the foliage or needles. They can consequently be controlled by using a stomach poison such as arsenate of lead, two pounds being used to fifty gallons of water. In controlling such an outbreak trees should be sprayed, if possible, before the caterpillars become of any size. The European pine- shoot moth {Evetria buoliana) at times does considerable damage to sapling pines. The larvae work in the new buds and shoots, resulting in crooked trees. This insect is controlled by pruning off all infested shoots. Several species of spittle insects are found on pine. The most common species belong to the genus Aphrophora. These insects are found under masses of froth-like spittle which appear on the new growth twigs. Whatever damage which may occur is localized to the twig on which the insect is feeding and as these are sucking insects the injury is further localized to the cells within the twig. The pine leaf miner {Paralechia pinifoliella) which is the minute larvae of a small grayish brown moth, whose wing expance is but three-eighths inch, at times becomes numerous enough to cause trees to turn brown. There are supposed to be several generations a year. The pine leaf scale {Chionaspis pinifoliae) at times becomes ex- tremely numerous so that small trees may even appear white due to the -large number of whitish scales occurring on the needles. This insect is best controlled by spraying the trees with Black Leaf Forty. It would, of course, only be in connection with transplants or ornamental trees that spraying would be advisable. INSECTS ATTACKING MATURE TREES Healthy mature white pine trees are seldom killed outright by insects. It is usually trees that have first been weakened by drought, fire, smoke, or over-maturity, which are seriously attacked and finally killed by in- sects. Weakened trees attract large numbers of in- 42 jurious insects which usually soon destroy them so that they are practically of no use for lumber purposes. The ■ gipsy moth at times does do considerable damage to healthy trees growing in mixture with hardwoods or in close proximity to them. At times saw-fly larvae may defoliate and kill large pine. BARK BEETLES Usually the first insects to attack the weakened pine are bark-beetles. These are small, oblong, hard-shelled insects usually from one-eighth to three-sixteenths inch in length. These beetles make tortuous galleries beneath the bark in which the eggs are laid. These eggs hatch into minute white grubs which burrow in all directions beneath the bark loosening it from the trees. There are several species commonly found attacking the pine in New England. Ips pini is probably the most common bark beetle found in pine. Three species of Tomicus are also commonly found attacking pine. These beetles multiply rapidly in spite of the fact that there is usually but one generation a year. PINE BORERS The greatest damage to the trees comes from wood- boring larvae. These are of two general types — the round-headed borers and the flat-headed borers. The first type are usually the larvae of Monochamus or the so-called round-headed borers. There are three species commonly found attacking the pine — one brown {M. notatus), one black (M. scutellatus), and one mottled gray (M. titillator), which are described under spruce and fir wood borers. These beetles particularly attack logs piled in the sun, or dying trees, and can be heard boring in the wood for quite a distance. The ribbed ragium {Rhagium lineatum) is also freciuently found burrowing beneath the bark of white pine. The adults of the second type, or flat-headed borers, are usually broad, 43 elongate, rather flat bodied beetles, generally of a bronzed or metallic color. The larvae, or grubs, are much elongated and somewhat flattened. The head is small, although the body segments directly behind it are very broad, apparently forming part of the head. This gives them the name flat-headed or hammer-head borers. The most common species attacking pine are from one- half to one and one-half inches in length. The larvae start by tunneling directly beneath the bark, later boring down into the wood. They make broad, rather shallow burrows or tunnels which are filled with soft shaving like chips. In the woods these borers are held in check somewhat by birds and parasitic hymenoptera. These latter are fly-like insects which have long ovipositors, or tail-like appendeges, which they thrust through the bark of infested logs or trees in order to lay their eggs in the burrows of the wood-boring larvae. These eggs hatch into small grubs, which follow^ down the burrows and attack the larvae, boring into and eventually kiUing them. The parasites can usually tell fairly accurately just where the borers are working, probably due to the very perceptable rasping sound, caused by the chewing of the larvae. The eggs are consequently laid fairly close to the places where the borers are working, if not at times directly in the borers. CARPENTER ANTS Next in importance are the large black, or black and red, carpenter ants. These seldom attack a healthy tree, usually entering through decayed places or attacking felled trees. They are tireless workers and due to their great numbers soon honeycomb out a tree. It is quite common to find pine trees in the woods which have been hollowed out by these ants. 44 Control All of the above wood-boring insects, including the bark beetles and carpenter ants, are best controlled by immediately felling those trees which show signs of dying, and utilizing the logs before the larvae have an opportunity to do their damage. It is bad policy to leave pine logs lying around for any length of time during the warm season before sawing. Conifers which show signs of dying seldom recover, due to the small amount of reserve food present. They are therefore very sus- ceptible to adverse conditions. Dying trees left standing serve merely as breeding grounds for insects which are likely to spread into the surrounding healthy trees. If for any reason the dying trees can not be utilized, the mere felling and barking of the tree, combined if possible with burning of the slash, will aid materially in prevent- ing possible outbreaks. WOOLY APHID There are several insects, usually of minor importance, which at times may become numerous enough to be a menace to the incipient forest. Among these the pine bark aphid, or wooly aphid {Chermes pinicorticis) is probably the most commonly found in the forest. This aphid appears as white tufts at the base of the needles on twigs, and as white flocculent patches on the bark of the trunks and branches. This insect undoubtedly checks the growth and lessens the vitality of the trees and at times may even kill them. In the forest it is questionable if it is ever necessary to carry on extensive control measures against this particular insect. The writer has, however, seen local infestations where it would have been advisable to cut out the infested trees and destroy them by burning, or else by utilizing the cut timber. Individual trees are at times sprayed with kerosene emulsion, which is very effective in controlling the aphids. Other insects which might be mentioned are white ants, several foliage feeders, and a few which feed upon the roots. 45 In spite of the somewhat formidable array of insect enemies no apprehension is felt by the writer as to the possible danger from planting white pine. It is true, however, that the planting of this species to the exclusion of other forest trees is highly undesirable from an ento- mological standpoint. A more extensive planting of red pine or spruce is worthy of serious consideration. There is a certain farming region in Massachusetts where very little white pine occurred. Twenty years ago large plantations were set out, and for years these escaped serious insect damage. Since that time an ever increasing number of plantations has been set out in this locality so that at the present time insects attacking the white pine have been attracted to this most favorable area in large numbers. The white pine weevil is particularly injurious, and has begun to attack even the older planta- tions. SUMMARY In concluding it might be well to summarize briefly just how plantations should be handled in order to prevent serious injury from insects. The seed beds should not be situated in close proximity to recently cut-over pine lands, that is within 200 yards of the nearest stumps, logs, or slash. If possible freshly plowed-under grass land should be avoided. It is best to use land that has pre- viously^ been cultivated. When setting out the plantation, cut-over pine lands should be avoided until the third year after cutting. Too much emphasis can not be laid upon the need of care in choosing the planting site and in the planting itself. There is no question but that weak trees are more susceptible to insect injury than vigorous growing ones. If a person is at all in doubt as to the proper site for planting, valuable information can be obtained by merely noting under what growing conditions the best stands of pine are found in that or similar locaUties. The fact that a white pine tree can be found in a swamp does 46 not signify that this is a favorable location for the tree, as some planters apparently believe. There is no question but that careful planting more than pays for the extra labor involved. Planting around ant mounds should either be avoided or else the colonies destroyed. It is the writer's behef that in order to overcome weevil damage, the trees should not be spaced any further apart than six by six feet. The increased value of the resulting stand should more than pay for any increase in cost of planting. The six by six foot spacing is almost universally used now. In the maturing stand, dead or moribund trees should be cut out and destroyed, as these merely act as centers of infestations. It was previously suggested that some emphasis should be placed upon the planting of other species of conifers. This suggestion does not, however, mean that the planting of white pine should in any way be curtailed, for insects attacking red pine or spruce would also become obnoxious if these trees alone were planted in any quantity. As near as possible the natural balance found in nature should be kept. This does not mean the planting of mixed plantations, for these are not so economically handled. It does mean, however, that large areas should not be given over to a single species, as this merely invites insect damage. Larch Insects LARCH SAW-FLY Between the years 1882-1885 the larch fly (Nematus erichsonii) destroyed practically all of the mature larch in the State. The destruction of the larch at this time is said to have been one of the prime factors bringing about the exodus of caribou from Maine into Canada, as these animals lived largely in the larch swamps feeding on the twigs and foliage of this tree. The saw-fly was again found active this summer in several localities where the larch is again becoming a dominant species making up, as it does in some parts of the State, fully one-quarter of the stand over wide areas. Several small outbreaks occurred during the summer of 1922. The large black adult saw-fly lays its eggs during the latter part of June and the early part of July in the terminal shoots of larch. The larvae are found active during July and early August. The full grown larvae are from one-half to three-quarters of an inch in length. They are easily recognized by the round jet-black head and the dull light green bodies. There are three pairs of black thoracic legs and seven pairs of short abdominal legs. As is the case with other saw-fly larvae they have the habit of curling up the head and rear end of the body into a "U" shape when disturbed. LARCH CASE BEARER Considerable attention was called to the browning of the larch, or tamarack, in Maine during 1922. In many localities large stands of larch appeared in July as if a fire had swept thru, whereas a few weeks previous they 48 had been green. In places where the larch occurred in large stands making up a high percentage of the forest whole hillsides and valleys looked brown. Examination of the stands of larch have shown that the trees are being attacked by a comparatively new insect to this region — the larch case bearer (Coleophora laricella). This insect is very common throughout Europe where it is a serious pest. It was probably brought into this country on European larch, a tree that is quite widely planted in the northeastern United States. There is but one generation of the insect a year. The small delicate gray moths started to emerge from the small cigar shaped cocoons about June twentieth. The moths, which are only about three-sixteenths inch in length, lay their eggs on the new needles and the young larvae upon hatching immediately begin to tunnel or mine within the needles, causing them to turn yellow and then brown starting from the tips. When very numerous practically all of the needles on a tree may be injured and in many cases destroyed, as in the present outbreak. As soon as the mine is long enough to form a case, a portion of the needle is cut off and the larvae proceed with this protection to another leaf. When attacking a needle the larva first cuts a circular hole thru which its head and later its body may extend for feeding purposes. The case, which at first is whitish, gradually becomes gray with age, and is lined by the larva with silk. Upon the approach of cold weather the larvae carrying their cases retire to a sheltered place on the branches or beneath bark and lichens becoming active early in the spring when they continue feeding. There is at present every indication that considerable damage may be done to the larch, for the insect is be- coming extremely abundant. It is hoped that this coming spring something can be done to check the out- break. Hardwood Insects POPLAR OR ASPEN BORER Trees of the genus Popiiliis, which includes the aspen, popple, cottonwoods, poplars, and Balm of Gilead, are all subject to serious injury by wood-boring insects. As poplar is becoming an important pulp tree in Maine, even to the extent of being set out in plantations, some attention must be paid to holding these borers in check, for plantations are often completely destroyed. Probably the most injurious of these borers is the so-called aspen borer {Sapcrda calcarata), which is very common in Maine. The adult is a large, robust, grayish green beetle, approximately one inch in length with light yellowish spots on its wing covers. During July and August the beetles gnaw oblong scars in the bark in which they lay their eggs. These hatch in about twenty days and the young larvae begin mining beneath the bark where they remain over winter. In the spring the larvae bore into the sap and heart wood. Here the larvae remain boring until the second season following egg laying. During June or July of the third year the adults emerge. CONTROL The insect is best controlled in the forest by locating and then cutting the so-called brood trees which have been attacked for a number of years in succession and usually contain several generations of the insects. These trees are easily distinguished by the dead tops or limbs, the deformed trunks, or by the frass and brown sap exuding from the egg scars. These brood trees should be cut and burned or else the main trunks spUt and exposed to the sun, which will dry out the wood thus killing the brood. PLATE VIII. SHADE TREE INSECTS. A. Larch Case Bearer, showing cases on needles. (| natural size). B. Larva of Forest Tent Caterpillar. (Natural size). C. Larva of Elm Leaf Beetle. (Slightly enlarged). D. Elm Leaf Beetle. (Slightly enlarged). E. Adult Poplar Borer. (Natural size). F. Work of Oak Twig Pruner. Twig has been split so as to show burrow and end of twig that was severed. (5 Natural size) G. Adult Oak Twig Pruner. (Natural size). H. Adult Maple Borer. (Natural size). I. Work of spruce Cone Worm showing castings around base of cones. 51 MAPLE BORERS Several wood boring insects do considerable damage to maples, particularly over mature trees. These trees should be cut and burned or utilized whenever possible, as should all trees heavily infested with borers. BRONZE BIRCH BORER There are large areas of white and yellow birch in the northern part of the State in which injury from the bronze birch borer (Agrilus anxius) is everywhere very apparent. The somewhat flattened, bronze-colored beetles lay their eggs in June in crevices on rough sur- faces of the bark. These hatch into flat creamy white grubs which bore thru the bark into the sap wood where zig zag tunnels are made. Damage shows up in the way of dead tops and in some areas of pure white birch hardly a tree has escaped injury. Poplar is also attacked. Trees occurring in mixture with softwoods are not so liable to injury. FOREST TENT CATERPILLAR Several thousand acres of poplar and white birch were stripped by the forest tent caterpillar {Malacosoma disstria) in 1922 in the region of Jackman, Lobster Lake, Chesuncook Lake, and Eagle Lake (T. 8, R. 12). Examinations of the stands in the fall showed that the insects had been heavily parasitised and it is beheved that the outbreaks will not prove serious. In one locality the severity of the outbreak made it seem ad- visable to cut the stand and this was done as a protection to surrounding timber. The location of the stand made it possible to utilize the wood for pulp. The brown eggs are laid in masses encircling the twigs. The caterpillars hatch out during April. When full grown they are from one and one-half to two inches in length. The head is blue and there is a row of white, diamond-shaped spots down the middle of the back. The larvae turn into moths during July. Unhke the apple tree tent caterpillar this species forms no tent. 52 POWDER POST BEETLES Very frequently considerable damage is done by powder post beetles to hardwood material in storage. There are several injurious species but in Maine the European Lyctus (Lycius linearies) is apparently the most common. This is a slender, somewhat flattened, rusty red brown beetle, from one-tenth to one-fifth inch in length. There are single rows of shallow punctures on each wing cover. The beetles lay their eggs in the sap wood of seasoned hardwood material of all kinds. Hickory, oak, and ash are particularly subject to injury but other woods are also attacked. The small, yellowish white larvae, upon hatching, immediately begin boring through the wood in all directions. When full grown the larvae are from one-eighth to one-fifth inch in length with three pairs of legs. The adults emerge in the early summer. Frequently the inside of the wood is reduced to powder before exit holes are apparent. Usually damage first shows up in the way of small piles of fine powder around the stored products. At times furniture and even build- ings have been known to crumble before the presence of the beetles has been realized. It is well to bear in mind that heart wood material is never attacked. Sap wood material which has been seasoned for less than eight months is also immune from injury. Material in storage should be classified, keeping that which is most subject to injury by itself. This should be inspected at least once a year, preferably in the winter. Material which has been attacked by the beetles should be immediately destroyed. The oldest stock in storage should be utilized and sold first. Care should also be taken to inspect all new stock being brought into storage. Shade Tree Insects SPRUCE GALL APHID The. spruce gall aphid (Chermcs abietis) causes con- siderable injury to Norway and while spruce used for ornamental purposes such as on lawns or as hedges. The galls usually occur near the base of the terminals and appear ver\' much like small cones. In the fall these turn brown. The main injury comes from dis- figurement to the trees, as the galls remain on the trees year after year. Infested trees should be sprayed in April, using a whale oil soap solution at a dilution of one pound of soap to two gallons of water. SPRUCE CONE WORM The spruce cone worm {Dioryctria reniculella) was very common in some sections of Maine in 1922. The amber brown larvae tunnel thru the new cones, often passing from one cone to another, and leaving unsightly masses of frass and castings around the cones. The larvae also feed on the foliage of terminal twigs, leaving masses of excrement and pitch on the sides of the twigs. When full grown the larvae are slightly over one-half inch in length. • The moths are of a stone gray color. Infested cones should be collected and burned. OAK TWIG PRUNER Numerous inquiries have been received in regard to the damage caused by the oak and maple twig pruner, (Elaphidion villosum). This insect in its larval stage bores thru the twig working towards the base of the small limb or twig in which it is boring. Upon reaching matur- 54 ity in the fall, it gnaws a circular groove extending to the bark and then retreats back into the burrow plugging it with sawdust. The twig is usually broken off by the first high wind and if examined will give every appearance of having been severed with a knife. The larva trans- forms into a pupa and beetle within the fallen twig, emerging about the first of June. At times the insect may do considerable damage to shade trees, but is easily controlled by collecting and burning the fallen* twigs either in the late fall or better still in the spring. ELM LEAF BEETLE The elm leaf beetle (Galerucclla luteola) was apparently very prevalent in the cities and towns of southern and central Maine in 1922. The small beetles emerge from hibernation at about the time that the leaf buds are beginning to open. They immediately begin feeding on the tender leaves making small, irregular holes. Eggs are then laid on the lower surfaces of the leaves and the young hatching out in about six days begin skeletoniz- ing the leaves. A second generation occurs in July. Most of the difficulty found in controlling this insect has been due to the fact that trees have not been sprayed at the right time. A difference of one week means the difference between success and failure. The trees should be sprayed just as the adults first begin feeding on the leaves, then again as the larvae are hatching, and a third spray may be necessary at the time that the second generation larvae are hatching. A fairly strong spray should be used, using four pounds of lead arsenate to fifty gallons of water. On the second and third sprays emphasis should be placed on spraying the under side of the leaves. BORERS A large number of inquiries have been received in regard to borers in shade trees — particularly maple, poplar, and elm. In general the treatment is similar for all. Wherever possible pruning and burning of 55 infested limbs is advisable, either in the late fall, early spring, or as soon as the injury shows up. In cases where the borers have entered the main stem or trunk, carbon bisulphid should be injected into the burrows, using from one to two teaspoonfuls to a hole and then plugging the hole in order to keep the gases from escaping. In some cases the larvae may be destroyed by forcing a flexible wire into the burrow. Painting freshly made egg scars with carbolineum is very efTective. LEAF SPOTS Many different fungi attack the foliage of shade trees causing small brown spots, or at times the entire leaves to turn brown and fall off prematurely. As most of these fungi pass the winter on the fallen leaves, the diseases are easily checked by raking these up and burning. Economic References Blackman, M. W. 1919. Report on the Spruce Bud Worm, Maine Forestry Dept. Craighead, F. C. 1922. Fighting Bark Beetles in Balsam. lUus. Can. For. Mag., Vol. 18, No. G, pp. 820-821. Craighead, F. C. 1922. Combatting Budworm Attack. Illus. Can. For. Mag., Vol. 18, No. 8, p. 942. Felt, E. P. 1906. Insects Affecting Park and Woodland Trees. Mem. New York State Mus., No. 8, Vol. I, pp. 59, 170-171, 189. Hofer, G. 1920. The Aspen Borer and How to Control It. U. S. D. A. Farmers' Bui. 1154. Hopkins, A. D. 1909. Bark Beetles of the Genus Dendroctonus. U. S. D. A. Bur. of Ent. Bui. 83, Part 1. Hopkins, A. D. & Snyder, T. E., 1917. Powder Post Damage by Lyctus Beetles to Seasoned Hardwood. U. S. D. A. Farmers' Bui. 778. 56 Johannsen, D. A. 1913. Spruce Budworm cS: Spruce Leaf Miners. Maine Agr. Exp. Sta. Bui. No. 210. Packard, A. S. 1890. Insects Injurious to Forest and Shade Trees. Fifth Kept. U. S. Ent. Comm., pp. 791-792, 811-822, 830-839, 854-856, 879-890. Peirson, H. B. 1920. An Infestation of the White Pine Aphid. Psyche, Vol. 27, Nos. 2-3, pp. 62-63. Peirson, H. B. 1921. The Life History and Control of the Pales Weevil. Harvard Forest Bui. No. 3, Peters- ham, Mass. Peirson, H. B. 1922. Control of the White Pine Weevil by Forest Management. Harvard Forest Bui. No. 5, Petersham, Mass. Peirson, H. B. 1922. Mound Building Ants In Forest Plantations. Journ. of Forestry, Vol. 20, No. 4, April. Peirson, H. B. 1922. Forest Insects in the Northeast, Amer. For. Mag., Vol. 28, No. 346, pp. 628-634. Peirson, LI. B. 1922. Larch in Maine Threatened By Insect Depredation, Amer. For. Mag., Vol. 28, No. 347, p. 666. Schierbeck, O. 1922. Treatise on the Spruce Bud Worm, Bark-Beetle, and Borer, Montreal. Swaine, J. M. 1918. Canadian Bark-Beetles. Part 2, Ent. Branch Dept. of Agr., Tech. Bui. No. 14, Ottawa, Can. Swaine, J. M. 1922. Insect Armies that Follow in the Wake of Fire. Illus. Can. For. Mag., p. 666. CONNECTICUT AGRICULTURAL EXPERIMENT STATION NE\V HAVEN, CONN. BULLETIN 155, MAY, 1907. ENTOMOLOGICAL SERIES, No. 14. The Elm Leaf Beetle CONTENTS. Page. The elm leaf beetle 3 History and distribution in America 3 Life history and habits 5 Description 7 Effect upon the trees 8 Food plants 8 Number of generations 9 Natural enemies 9 Remedies 10 Spraying with poison 10 Destroying the pupae 12 Destroying the adult beetles 12 Outfit for spraying elm trees 12 Summary 13 The Bulletins of this Station are mailed free to citizens of Con- necticut who apply for them, and to others as far as the editions permit. CONNECTICUT AGRICULTURAL EXPERIMENT STATION. BOARD OF CONTROL. His Excellencj', Rollix S. Woodruff, Ex officio, President. Prof. H. W. Conn Middletown. Prof. W. H. Brewer, Secretary New Haven. B. W. Collins Meriden. Charles M. Jarvis Berlin. Edwin Hoyt New Canaan. J. H. Webb Hamden. E. H. Jenkins, Director and Treasurer New Haven. STATION STAFF. Chemists. Analytical Laboratory. John P. Street, M.Sc, Chonist in charge. E. }^IoxROE Bailey, M.S. E. J. Shanley, Ph.B. Kate G. Barber, Ph.D., Microscopist. Laboratory for the Study of Proteids. T. B. Osborne, Ph.D., Chemist in Charge. C. A. Brautlecht, Ph.B. Botanist. G. P. Clinton, S.D. Entomologist. W". E. Britton, Ph.D. Assistant in Entomology. B. H. Walden, B.Agr. Forester. Austin F. Hawes, M.F. Agronomist. Edward M. East, M.S. Stenographers and Clerks. Miss V. E. Cole. Miss L. M. Brautlecht. Miss E. B. Whittlesey. In charge of Buildings and Grounds. William Veitch. Laboratory Helper. Hugo Lange. Sampling Agent. V. L. Churchill, New Haven. The Elm Leaf Beetle. BY W. E. BRITTOX, state Eiitoiiiolosiist. Twelve years ago an account of this insect was published by this Station in Bulletin Xo. 121, which has for some time been out of print. Since then only a few scattered notes have appeared in the bulletins and reports. The object of the pres- ent paper is to place in the hands of the people of Comiecticut a fairly complete and comprehensive account of the elm leaf beetle with up-to-date remedies and methods of treatment. There is a constant demand for such information from public school teachers, members of village improvement societies, and men employed in the street and park departments of our cities and towns, as well as from private individuals who desire to give the best care to trees on their home grounds. HISTORY AXD DISTRIBUTIOX IX A:MERICA. The elm leaf beetle was introduced into this country probably more than seventy years ago. In its native countiy, Europe, where it had long been known, it had from time to time caused serious injur}- in Italy, Austria, and the southern portions of France and Germany. In Northern Europe the insect occurs sparingly, but can hardly be called a pest. Harris states* that the elm leaf beetle attacked and seriously injured the elm trees of Baltimore, Md. in 1838 and 1839. The beetle seemed to spread chiefly northward, though slowly, until Southern New England was reached in the early nineties, and much damage done. In the coast towns of Connecticut many fine old elms, including some historic trees, were killed by its depredations. * Insects Injurious to Vegetation, page 124. 4 CONNECTICUT EXPERIMEXT STATION BULLETIN I55. Stamford, Norwalk, Bridgeport, Stratford, Milford and New Haven especially lost many noble trees. Later the inland cities were invaded, and the elm trees ravaged. In New Haven the pest was perhaps at its worst in 1895 ^^^^ 1896. In 1896 many of the trees on the older streets about the center of the city were sprayed with poison by the street department. The following season the pest was less serious, and continued to subside until 1901, when it was again comparatively destructive. From Fig. I. — Elm leaves showing larvae and the damage which they do by feeding on the under surface, natural size. 1902 it diminished in abundance until 1906, when considerable damage was done to the trees. So far as is known the distribution of this insect in America is confined chiefly to the lower altitudes of Southern New Eng- land and the Alleghanian region. From Charlotte, N. C, its southern limit, the elm leaf beetle now extends as far north as North Conway, New Hampshire. Up to this time, however, the beetle has done no particular damage in New Hampshire. Regions generally infested include the whole of Massachusetts, THE ELM LEAF BEETLE. 5 Rhode Island, Connecticut, southeastern New York, New Jersey, eastern Pennsylvania, Delaware, Maryland and a por- tion of Kentucky, though isolated outbreaks have occurred in western New York, Pennsylvania, West Mrginia, Ohio and North Carolina. It is of course found in Virginia, Vermont, New Hampshire, and probably in Maine. Kentucky, therefore, contains the western limit of the distribution of this insect, though we may expect that soon adjoining states may become infested. The insect exhibits a marked tendency to spread farther along river valleys than over mountains, and is dis- tinctly a pest of city and village trees rather than of trees in the open fields and roadsides of the country. Fig. 2. — Cluster of eggs, greatly enlarged. LIFE HISTORY AND HABITS. The overwintering beetles come out of their winter quarters during the warm days of early spring, mate, and as soon as the leaves unfold they begin to eat small round or oval-shaped holes through them. ]\Iany leaves are thus riddled as though shot had been sent through them, and appear like the illustra- tion on the front page of this bulletin. During the latter part of May and early in June the females deposit small clusters of yellow eggs on the under sides of the leaves. The period of ovipositing extends over about four weeks, and each female mav lav five or six hundred eggs. In 6 CONNECTICUT EXPERIMENT STATION BULLETIN 1 55. about a week the eggs hatch and the young larvae or grubs feed upon the under surface of the leaves, eating off the green tissue between the veins and leaving the veins and the upper epidermis, as is shown in Fig. i. In about three weeks the larvae or grubs are fully grown, and crawl down the trunks of the trees or drop from the ends of the branches to the ground and transform to the naked pupa stage. The great proportion of the pupae are found close around the base of the tree or lodged in the crevices of the rough bark of the trunk and larger branches. Except for being • • i J Fig. 3. — Larvae and pupae, twice natural size. in crevices, thev are unprotected. The writer has seen trees in New Haven where it would be possible to gather several quarts of these pupae at the base of a single tree. The pupa stage lasts about ten days, then the adult beetles appear, and lay eggs for the second generation, which seldom does much harm in Connecticut. Those emerging late prob- ably do not lay eggs for a second brood, but may be seen crawl- ing and flying about for a time, feeding more or less, but early going into winter quarters, usually in church belfries, attics of houses, barns, sheds or other out-buildings. They also pass the winter in cracks of fences, telephone poles, or under the edges of the loose bark of the trees. In some of the cities worst infested the adults sometimes gather in church bel- fries in such numbers that they can be swept up by the half THE ELM LEAF BEETLE. 7 bushel. The ehii leaf beetle often occurs with the two-spotted lady beetle in dwellings, simply because they both seek the same kind of a place for hibernation. Correspondents frequently send both species to the writer and desire to know if they are not in some way responsible for the injuries to their carpets. There is, of course, no relationship or similarity in food habits of the three species. The lady beetle is predatory, and in the larval stage destroys numbers of plant lice, and therefore should never be destroyed. The elm leaf beetles should, of course, be killed wherever thev are found. DESCRIPTION. The eggs are bright yellow in color, bottle-shaped, and resemble the eggs of the Colorado potato beetle, but are smaller. They are fastened vertically to the under side of the leaf in clusters of from five to twenty-five arranged in two or three irregular rows. When first hatched, the larva is dark or nearly black, covered with tubercles bearing black hairs. As the larva increases in size it molts several times and on becoming full-grown is about one-half inch long, dull yellow in color, with a pair of longi- tudinal black stripes along the back. Head, legs, lateral tuber- cles and two rows of small tubercles between the dorsal stripes are black. The tubercles also bear black hairs. The pupa is about one-fourth inch in length and bright orange yellow in color, with black hairs or spines. It is not enclosed in an earthen shell to protect it, but is found at the base of the tree perfectly naked and wholly unprotected. The adult beetle is light yel- low in color when it first emerges, but soon takes on a duller hue, and finally becomes a dull olive green. An indis- tinct black stripe extends from the base to the extremity of each wing cover just inside of the margin. Small black spots or markings on the pronotum of the thorax vary greatly in size and shape. Legs and antennae are yellow. Fig. 4.— Adult natural size. beetles, twice 8 CONNECTICUT EXPERIMENT STATION BULLETIN 1 55. EFFECT UPON THE TREES. It has previously been mentioned that the adult beetles do more or less feeding, always eating holes entirely through the leaves, as is shown on cover of this bulletin. This of course injures the tree, but is much less serious than the damage caused by the larvae, which eat away the under surface of the leaves. The larvae are always more abundant than the adult beetles, and are more voracious in their feeding habits. The worst infested trees usually drop their leaves in Connecticut about the middle of July. If this happens, and is followed by a rainy season, new leaves will be put out, but in a season of a protracted drought the trees may fail to put forth new leaves. In either case the tree is undoubtedly weakened, and often seri- ously so. Sometimes the second crop of leaves is devoured by the second generation of beetles, but in Connecticut the white fungus mentioned in another part of this bulletin is apt to serve as an important check to the beetle in a wet season. Two complete defoliations, one succeeding the other, usually kill a tree. Usually, however, the defoliation is not quite complete, and the trees continue to exist in a greatly weakened and devitalized condition. In the cities and larger towns, on account of further injuries* by horses, by leaky gas pipes in the ground, and pave- ments which cut ofif the supply of moisture, many trees have died. In 1901 the writer was called to Norwich, where nearly every elm had died for a distance of about one and one-half miles on a prominent residential street. These trees had been weakened by the constant attacks of the beetle year after year, and a leaky gas main finally destroyed what little vitality remained. Most of the maple trees along the street survived. In many cases young or newly planted trees seem to be especially subject to attack, and therefore should receive extra attention. FOOD PLANTS. Elms constitute the only food plants known for this insect, and the European species suffer more than the American ones. The English elm (Ubniis campestris) and its weeping variety * For a discussion of these injuries the reader should consult Bulletin 131 of this Station. THE ELM LEAF BEETLE. 9 known as the Camperdown elm are favorites of the beetle. The writer has seen these trees entirely defoliated in New Haven when the common white, or American elms, were uninjured. The American elm is, however, the next choice, followed by the Scotch elm (U. montana), and though no variety is wholly exempt from attack, the winged elm (U. alota), the slippery elm (U. fulva), the cork elm (U. siiherosa) and the rock elm {U. racemosa) are much less frequently attacked. NUMBER OF GENERATIONS. According to Burgess,* "in New Jersey, Professor J. E. Smith has recorded only a single brood and sometimes a partial second brood, while in the latitude of Washington, D. C, according to the observations of Messrs. Riley, Howard and Marlatt, of the Division of Entomology, two annual broods and sometimes a partial third brood have been found." Dr. E. P. Felt, State entomologist, of Albany, N. Y., findsf two well marked broods and a partial third brood at Albany and Troy, N. Y. The writer has not followed out this matter carefully in Connecticut, but all stages are found on the trees during the first half of September, so presumably there are at least two broods, but the egg-laying period of the adults is so prolonged that the lines of demarcation are nearly obliterated. In Con- necticut the leaves of the trees severely attacked by the first brood generally turn brown and drop about the middle of July, when the larvae are descending the trees to pupate. NATURAL ENEMIES. One of the most important natural enemies of the elm leaf beetle in Connecticut is a ftmgus known to botanists as Sporo- trichum glohuliferum Speg. {S. cntoinopliihun Peck), which attacks the pupae and adults in late summer, especially in a moist season. In 1902 this fungus was prevalent, and the fol- lowing season the elm leaf beetle did little damage to the trees. In 1906 the beetles were abundant, but as the month of July was * Bulletin No. 4, page 17, Ohio Dept. of Agriculture, Div. of Nursery and Orchard Inspection. 1905. t Bulletin No. 57, N. Y. State Aluseum, p. 14, 1902. lO CONNECTICUT KXPERIMENT STATION BULLETIN 1 55. wet, the fnng"us developed and killed a great many beetles. Beetles attacked by this fungus are covered with white mold, as shown in Fig. 5. Predatory bugs of at least three species of the genus Podisiis feed upon the larvae and pupae, and Riley* records three species of beetles that also devour full-grown larvae and pupae. The praying mantis (Stagnioinaufis Carolina Linn.) is also an enemy of the elm leaf beetle in the southern portion of its rang^e. Fig. 5. — Pupae and adults killed b}- fungus. Healthy specimens at the left, natural size. REMEDIES. Spraying zvith poison. Covering the foliage with some arsenical poison is the only sure means of preventing injury to the trees, and for this purpose arsenate of lead is unquestionably the most satisfactory of these poisons. It remains better in suspension and adheres to the foliage longer than Paris green or London purple, and is less liable to injure it. As there are now several brands of good arsenate of lead on the market, it * Div. of Entomology, U. S. Dept. of Agriculture. Bulletins No. 6, p. 10 and No. 10, p. 13. THE ELM LEAF BEETLE. II will no longer pay to make it up each time from lead acetate and arsenate of soda. The arsenate of lead made by the Merri- mac Chemical Co.. Boston, Mass. ; Schbonmaker & Son, Cedar Hill-on-Hudson, N. Y., and the Bowker Insecticide Co., Boston, Mass., (Disparene) have all been used in our tests and have given satisfaction. Arsenate of lead should be used in the following proportions : — „ , I Arsenate of lead 3-5 lbs. Formula^ „, , [ Water 50 gals. There are two methods of spraying elms: (i) To spray as soon as the leaves unfold, the treatment being aimed especially at the parent beetles, and to forestall all injury. As growth takes place, new leaves are constantly appearing, and these will not carry poison unless the application is from time to time repeated. This should be done often enough to ' keep the foliage well coated with poison until July ist, when growth usually ceases, and both sides of the leaves should be coated. (2) The other method is to spray the under sides of the leaves very thoroughly about June ist, or soon after the eggs begin to hatch. This treatment is aimed at the larvae, and sometimes a single spraying is sufficient, as the poison will remain throughout the season. By it the great bulk of damage wdll be prevented, but the leaves will show the small holes made by the parent beetles before the poison was applied. If arsenate of lead cannot be procured and it seems desirable to use other poisons, Paris green can be substituted. This should be used at the following rate : r Paris Green i lb. Formula -| Fresh lime 3 lbs. [Water 50 gals. Paris green is quicker in its action upon the insects than arsenate of lead, but will not remain as long upon the trees. Unless the lime is added, there is danger of "burning" the leaves. Lime is not needed wath arsenate of lead. The cost of spraying elm trees will vary from ten cents each in case of small trees to five dollars or more for the largest trees, according to the price of labor and the efficiency of the outfit. 12 CONNECTICUT EXPERIMENT STATION BULLETIN I55. Destroying the pupae. If the trees have not been protected by spraying-, and have been attacked and injured by a horde of beetles and their larvae, it is always advisable to destroy the insects in the pupa stage at the base of the trees, in order to reduce the crop for next year as much as possible. These can often be swept up in large quantites ; they can be killed by sprinkling them with hot water ; but best of all is to spray the ground not only close to the tree but as far away as the branches reach, and also spray the bark of the trunk and large branches, with kerosene emulsion or some other contact insecticide. The pupae are easy to kill, but as they remain in the pupa stage only about ten days, it is essential that this work be done at the right time, and it is only when we observe that most of the larvae descending the trunk have transformed to bright yellow pupae that we can know when is the proper time to act. Destroying the adult beetles. The beetles should of course be destroyed in attics, belfries and other places where they hibernate. This can best be done by sweeping them up before they become very active in spring and dropping them into the fire, hot water or kerosene to kill them. OUTFIT FOR SPRAYING ELM TREES. The barrel hand-power pump can be used for spraying small trees or for a limited number of large trees, but if one expects to make a business of spraying street trees, it will pay to pro- cure a power sprayer; this may be a steam or gasoline engine with pump, or what is perhaps better, the "Niagara Gas Sprayer," which utilizes cylinders of carbonic acid gas to furnish pressure, thus doing away with a pump. Each large village and city should have at least one power sprayer that can be put to immediate use for spraying street or park trees. Strong one-half inch hose should be provided in long lines of from fifty to two hundred feet, and from four to six of these can be attached to each power sprayer. Even a larger number might be attached, but while in operation some workmen would be in the way of others, so that nothing would be gained. Mr. H. L. Frost of Boston, who is in the spraying business, informed the writer that four lines of hose is about the most economical number for each outfit. Each hose is furnished with an extension rod with closing valve at the lower end THE ELM LEAF BEETLE. 1 3 and a cluster of nozzles at the upper end. These rods should be of different lengths, from four to twelve or fourteen feet for the different kinds of work. Any of the standard nozzles such as "Vermorel," "Mistry," or "Spraymotor" will be found satisfactory, and if several are used together in a cluster one is able to cover more leaf surface in a given time. For getting about in tall trees it will be necessary for the men to be provided with climbing irons and extension ladders. SUMMARY. The elm leaf beetle was introduced into this country from Europe about seventy years ago, and caused serious injury to trees at Baltimore, Md., in 1838 and 1839. From this point it spread slowly, chiefly to the northward, reaching Connecticut in the early nineties, and injuring and killing many fine old trees in the coast towns. Later, inland towns were attacked, and the trees ravaged. The insect is now found from Charlotte, N. C, as far north as North Conway, N. H., and as far west as central Kentucky, but has not proven destructive to elm trees north of Massachusetts. It is preeminently a pest of shade trees in cities and towns, and seldom injures trees in the open fields. Since 1896 the attacks have diminished, but the pest was again serious in 1906. The winter is passed by the adult beetles in attics, belfries and cracks in fences, and they come forth in April, and later feed and lay their yellow eggs upon the unfolding leaves. Beetles eat holes through the leaves, eggs hatch in a week, and the larvae eat off the green tissue from the under surface, caus- ing the leaves to turn brown and fall about the middle of July, at which time the larvae are about full grown. Then they descend to the base of the tree and transform to naked pupae ; ten days later the adult beetles emerge and lay eggs for the second brood or go early into winter quarters. Two complete defoliations in succession will kill a tree. Hozv to Fight the Elm Leaf Beetle. (i) Search all attics, church belfries and cupolas for the dormant beetles in winter and early spring. Sweep them up and burn them. 14 CONNECTICUT EXPERIMENT STATION BULLETIN I55. (2) Spray the leaves with poison as soon as they have opened, if their shot-hole appearance shows that the beetles are there in abundance, and the under sides of the leaves should be coated about June ist to destroy the larvae or grubs. (3) When, later in the season, the yellow pupae appear on the trunks of trees and the ground beneath, kill them with a spray of kerosene emulsion or by sweeping them up and burn- ing or soaking with kerosene. The first and third measures should be taken by each house- holder, church or social organization, at individual expense. The spraying, which is difficult and expensive if the trees are large, can only be done by concerted action of the town or borough authorities. For extensive spraying work power sprayers are desirable, but small elms or a few large trees can be treated successfully by means of a hand pump of barrel size. The "Niagara gas sprayer" in operation is shown in Fig. 6. Bulletin 454 October, 1926 The Spruce Gall-Aphid Glenn W. Herrick and T. Tanaka A GROUP OF GALLS ON SPRUCE IN JULY Published by the Cornell University Agricultural Experiment Station Ithaca, New York Received for publication April 10, 1926 THE SPRUCE GALL-APHID (Adelges abietis Kaltenbach) Order, Homoptera Family, Phylloxcridae Glenn W. Herrick and T. Tanaka Certain of the native spruce trees in this country, and one introduced species, the Norway spruce, are infested with a species of aphid, Adelges abietis, which causes galls of a familiar pine-apple type on the branches. The Norway spruce is especially subject to the attacks of this pest. All' of the spruces, because of their evergreen character and their dense and! shapely growth, are attractive trees in the plantings of both small and large grounds, and are useful for windbreaks in various situations. The Norway spruce is often used for hedges, but various factors contribute to its undesirability as a hedge plant, notably the injuries produced by the gall- aphid. HISTORY, DISTRIBUTION, AND INJURY It is not possible to give a detailed history of the spruce gall-aphid in America because the insect has been confused in the literature with other closely related species and one cannot be sure of the species under dis- cussion. It was certainly introduced from Europe probably many years ago. It is widely distributed in the northeastern United States and in southern Canada. Just how far west it extends, we have no accurate means of knowing. It has a wide distribution in New York, for the typical galls have been received from many different localities. It ap- pears to be more common and injurious in New York, Pennsylvania, and the New England States, than in any other part of the United States. In this country the insect attacks particularly the Norway spruce (Picea Abies) and the white spruce (Picea canadensis). Britton (1924) records it as attacking also the black spruce (Picea mariana), the red spruce (Picea rubra), and sometimes the hemlock (Tsuga canadensis). The Colorado blue spruce (Picea pimgens) is infested with a closely related species of gall-aphid (Chermes cooleyi Gillette), which causes galls on the branches similar in appearance to those of the spruce gall-aphid but longer and nearly always at the ends of branches, as shown by Gillette (1907-08). The spruce gall-aphid is seriously injurious to Norway spruces especially, and is particularly harmful to young trees. There may be hundreds of the galls on a single small tree. Miss Patch (1909) counted 990 fresh galls on a white spruce three feet tall. The writers have seen as many on Norway spruce. In cases of such severe infestation, many of the branches are usually killed and often single young trees in hedges are killed outright, although the crowding and pruning undoubtedly contribute to the unhealthy condition of the plants. When branches are severely infested with the galls, they begin to shed their leaves and the tree becomes 4 Bulletin 454 ragged and unsightly in appearance. The work of the insect is a distinct handicap to the nurseryman, because customers do not Uke to purchase trees already infested with the unsightly galls, and they really should not accept infested trees unless they feel inclined to take vigorous measures of control after the trees have been set. The effect of the galls is to cause trees to become deformed and misshapen, thus detracting from their beauty and attractiveness. SCIENTIFIC AND COMMON NAMES ■ This aphid, together with other closely related species, has been placed heretofore in the genus Chermes, and this particular species has been "known as Chermes abietis. It is found under this name in the references 'cited herein, in all except one instance. Comstock (1924) says it has been determined that the name Chermes should be applied to certain jump- ing plant-lice of the family Chermidae formerly known as the Psyllidae, and that those insects found on conifers which have been "quite generally known" under the generic name Chermes should be placed in the sub- family Adelginae. Therefore the forms on conifers heretofore known as Chermes will fall in the genus Adelges, and the species under discussion will be known as Adelges abietis. The insect has been given several common names — spruce gall -louse, European spruce bud-louse, yellozv chermes, green-imnged chermes, and grecn-tvinged adelges. It seems to the authors that the common name spruce gall-aphid comes nearer to expressing the common and distinctive characteristics of the insect than any of the other names mentioned. The insect is an aphid, and its peculiar, distinctive, and commonly known injury to its food plant is in the form of a gall. The name spruce gall- aphid, therefore, indicates at once its food plant, its character and position among insects, and the form of its injury. DESCRIPTION OF FORMS The wingless oviparous female The body of the adult wingless oviparous female is grayish green and is covered with a white waxy pulverulence which increases with age. The groups of pores are dark, and the mouth parts, antennae, and legs are dark brown. The body is more or less globular and oval as viewed from the dorsum. It is from 1.5 to 2 millimeters long and from 1 to 1.5 mil- limeters wide. The head and the thorax are closely joined, and there are three trans- verse rows of groups of dorsal pores in this region. The mesothorax, the metathorax, and each segment of the abdomen, bear a transverse dorsal row of groups of wax pores. The groups of pores are arranged on the body in six longitudinal rows, four rows along the dorsum proper and one additional row along each side of the body. Near the caudal end of the body the two side rows disappear. The number of wax pores in each group is large, but is not the same in all of the groups. The wax pores are not so numerous on the ventral side of the body, although there are from two to four groups on most of the segments. There are two The Spruce Gall-Aphid 5 pairs of spiracles on the ventral side of the thorax, and at least four pairs on the abdomen. The antennae are short but conspicuous. The first segment is short and thick, the second is slightly longer but somewhat slenderer, while the third and last is as long as or longer than the first two. The stylets of the mouth parts are very long. The legs are short and are wholly con- cealed beneath the body. The tarsi are two-segmented, with the first segment very short. The eggs of the ivinglcss hibernating female The eggs of the wingless hibernating female are laid in clusters of from 150 to 200, or even more, beneath the body of the female. They are oblong elliptical in shape, and greenish yellow in color when first laid. Later they turn darker, but they become yellowish again just before hatch- ing. Each egg is furnished with a slender white waxy thread at least twice as long as the egg itself. This thread seems to be entangled among and connected with other longer threads underlying the batch of eggs and holding the mass fast to the branches. The actual measurements of different eggs are as follows: 0.30X0.15 mm. 0.32 X 0. 165 mm. 0.30X0.155 mm. 0.34 X 0. 165 mm. 0.30X0.16 mm. 0.34 X 0. 170 mm. TJic first-instar tiyuiph The newly hatched nymph is yellow in color and the appendages are more or less transparent. The eyes are dark and each one seems to pos- sess three facets. The antennae are three-segmented, the first two seg- ments being short and the third one being longer than both of these together. There are no wax pores on the body. ' Different individuals measure as follows : 0.42X0.20 mm. 0.47X0.22 mm. 0.42X0.22 mm. 0.49X0.23 mm. 0.45X0.21 mm. The second-instar nymph The general color of the body and appendages in the second-instar nymph is very similar to that of the first-instar nymph, except that the body is now covered with a fine whitish waxy powder. The wax pores are therefore present, but they are not highly developed except on the head and the prothorax, where they are conspicuous. The measurements of individuals are as follows: 0.27X0.51 mm. 0.32X0.64 mm. 0.28X0.56 mm. 0.34X0.64 mm. 0.29X0.61 mm. 0.36X0.67 mm. The third-instar nymph The body of the third-instar nymph is yellowish green and is covered with a white powdery secretion of wax. The appendages and the mouth 6 Bulletin 454 parts are light brown. The wax pores are well developed on the anterior part of the body. The nymph usually carries a cast skin, and sometimes two of them, attached to the posterior end of the body. These skins are filled with liquid and are more or less globular in shape. Individuals of this stage measure as follows : 0.37 X 0 . 80 mm. 0.48 X 0 . 96 mm. 0.40 X 0 . 80 mm. 0.50 X 0 . 99 mm. 0.40X0.82 mm. 0.53X0.99 mm. 0.40 X 0 . 88 mm. 0.58 X 1 . 09 mm. 0.44X0.88 mm. The fourth-instar nymph, or pupa In the nymph of the fourth instar, the body is stout and the wing-pads are well developed. The nymph is yellow in color and noticeably pulveru- lent. The eyes are black and prominent, and the legs are dark. This stage, which is of long duration, enables the nymph to grow considerably, and the individuals vary greatly in size. The following measurements show the variation in size: 0.68X1.32 mm. 0.90X1.99 mm. 0.78X1.61 mm. 0.90X2.02 mm. 0.80X1.75 mm. 0.94X2.10 mm. 0.85X1. 90mm. 1.03X2.21 mm. The antennae are similar to those of the preceding instar, and the pro- thorax is fairly well differentiated from the fused meso-metathorax. The wing-pads of the mesothorax are large and extend to the middle of the second abdominal segment, while the hind wing-pads are smaller and are usually concealed beneath the front ones. The situation of the wax pores are well described by Miss Patch (1909) as follows: Head with an anterior group of pores near base of each antenna and two median groups at posterior margin ; prothorax with lateral gland area, an anterior median pair of groups, a small group (4 pores) between the lateral and median ones, and four groups near posterior margin of prothorax ; mesothorax with an anterior lateral area ; metathorax with two separated median groups ; abdomen with small and widely separated median groups on segments I-VI, those on I being composed of about 6 pores, those on II of 3 and those of III-VI of 2 each, a very small group of lateral pores occur on segments II-IX (merged to a caudal group on IX), and about half way between the median group and lateral margin an additional group of about 3 pores occurs on segments I and II. The smallness of these inconspicuous groups is correlated aptly with the fact that this is not a flocculent species, the wax secretions not exceeding the pulverulent condition. The zvinged oviparous female In the winged oviparous female, the wings have an expanse of from 5.4 to 6.3 millimeters. The head is dark brown and about three times as wide as its length. The compound eyes are prominent and black. The antennae are smoky yellow and five-segmented ; the first segment is short and stout, the second is longer than the first but less in diameter, the third is longer than the second, and the fourth and the fifth are sub-equal in length but are longer th:in the third (figure 1). Miss Patch (1909) says: The Spruce Gall-Aphid ^^of- Figure 1. the spruce gall-aphid ILS, The winged female, which emerges from the gall in August. 116, Antenna of the winged female. 117, The pupa, which develops in the gall (From Bulletin 173, Maine Agricultural Experiment Station) "The sensorium of each of antennal joints III-V is confined to the distal half of the joint and extends not more than half way around the joint." There is a group of smaller sensoria on V. The prothorax is smoky greenish yellow, with a dark triangular area in the middle of the dorsum ; the mesothorax is pale yellow, with a dark tri- angular area near the front margin in the middle. Near the caudal border of the metathorax is a subquadrangular dark transverse plate. In the normal position the wings are folded along the abdomen in a roof -like manner. The fore wing has a wide green costal margin and a green stigrna. The legs are slender and yellowish. The tarsi are two-segmented, with the basal segment very short and small and often concealed beneath the tip of the tibia. The abdomen is smoky yellow, with segments fairly dis- tinct. The groups of wax pores "are much as in the pupa except for the abdomen which is as follows : I with median groups comparatively large and merged, II median groups separated and composed of 2 pores each, V with two small groups between median ones referred to. I-VIII with distinct lateral groups on darkened area, III-VI with small groups of 2 or 3 pores each midway between median and lateral groups" (Patch, 1909). Bulletin 454 The measurements vary as follows Length of body 1.58 mm. 1.73 mm. 1.88 mm. 1.91 mm. 1.92 mm. 1.98 mm. 2.07 mm. 2.10 mm. Expai ,nse of wings 5.4 mm. 5.7 mm. 5.8 mm. 6.0 mm. 6.2 mm. 6.3 mm. The eggs of the zvinged oviparous female The eggs of the winged oviparous female are laid beneath the body of the female, while she sits lengthwise of a leaf, in a cluster of from 40 to 50. They remain covered with the dead body of the female, together with what waxy threads she may have secreted. They are dull yellow at first, and later become darker. Each egg is furnished with a waxy thread at one end. The eggs measure as follows : 0.18 X 0.34 mm. 0.20 X 0.36 mm. 0.18 X 0.36 mm. 0.20 X 0.38 mm. 0.18 X 0.38 mm. 0.22 X 0.34 mm. The first-instar nymph of the hibernating oviparous female In the first-instar nymph of the hibernating oviparous female, the body is slender and the ap- pendages are rather long. The body is light yellow when first hatched, but later, becomes darker and somewhat green. The an- tennae are long and are composed of three segments, the first and second of which are short while the third is comparatively very long. The groups of wax pores are conspicuous and abundant. In general, they form six longi- tudinal rows as seen from above, four rows situated medianly and one row on each lateral edge of the body. There are usually four pores in each group of the me- dian rows on the head, the thorax, and the first segments of the abdomen, but on the posterior -, ^ segments of the abdomen there Figure 2. first-instar nymph of the over- ^ f ^ u. <. ^v. c i WINTERING FEMALE, THE FORM WHICH ^^'^ more olteu Dut tttrcc porcs m PASSES THE WINTER ON THE SPRUCE a group. Each of the lateral The Spruce Gall-Aphid . 9 groups tends to have numerous pores. This form (figure 2), which passes the winter on the hranches of the spruce at the bases of buds, secretes more or less wax in the form of white threads that usually cover the body. LIFE HISTORY The spruce gall-aphids pass the winter as first-stage female nymphs clus- tered in crevices of the stem about the bases of the buds. On severely in- fested spruces the overwintering forms are abundant, there being as many as twenty to thirty about one bud. When examined with a lens they are seen to be purplish gray, but to the unaided eye they resemble small grains of gunpowder. By May 5, in 1923, the spruce buds had begun to grow and many of the nymphs had molted. So far as the writers' observation^ have gone, but one molt has been found in this generation, but some molts mav have been missed. The females increase in size, and begin to secrete long, crinkly, curly, white, waxy hairs, and become bluish green in color. They all settle now at the bases of the developing branch buds. The weather continued cold after the above-named date, and the females remained rather stationary in development for a week. By May 16, how- ever, females were found which had just begun to lay eggs. The individuals develop fairly in unison, although there are belated ones here and there that are sometimes a week behind the earlier ones in depositing eggsT By the end of May, in 1923, nearly if not quite all were depositing eggs. There is some evidence to indicate that egg laying is influenced by the develop- ment and activity of the tree. The buds on some trees start much earlier than do those on others, and on ^ those trees which start early the aphids are found to be depositing [ eggs, while on the spruces, which are then still dormant, the aphids are inactive. At least this proved to be the case in some instances which the writers were fortunate enough to observe. Each female deposits from 150 to 200 or more eggs beneath her body. On May 18 a female under observation was observed to exude from the caudal end of the abdomen a drop of liquid which appeared to be evidence of a beginning of activity in egg laying. On the 19th she became covered with a secretion of waxy threads. On the 21st, eggs could be seen beneath the body. These increased in number until, by the 29th, 198 eggs had been laid, some of which had already hatched. It is difficult to deter- Figure 3. overwintering females be- mine the exact length of the egg- ginning to lay eggs, may 22 laying period, because the first The insects are covered with white waxy threads 10 Bulletin 454 eggs are completely hidden by the body of the female and it is not easy to determine when fresh eggs have been added to the mass already present. The period appears to range from eight to fifteen days. For the reasons just given, it is difficult to determine the total number of eggs laid by a single female, but the number certainly ranges from 150 to more than 200, and probably as high as 250. The eggs and the body of the female are covered by a white mass of waxy threads and are more or less completely hidden from view (figure 3). The eggs hatch in about one week. A female was removed from a batch of eggs on May 23. The eggs had been deposited on the 21st and 22d. On the 25th the light yellow eggs had turned green, and on the 26th the eyes of the embryo could be seen in some. On the 28th two eggs hatched, and on the 30th nearly all had hatched. The period of hatching, in this case, varied from seven to ten days, which is probably about the average period. Formation of the galls and development of the nymphs In 1923 the earliest nymph observed emerged from the egg on May 19. Others kept emerging up to June 5, by which time, in normal years, nearly if not quite all of the eggs will have hatched. The nymphs are active and they very soon crawl down behind the leaves of the buds, which have al- ready begun to enlarge at their bases. Formation of the galls Cooley (1897) says: A very young shoot broken out from the bud scales before any of the eggs have hatched shows the basal leaves on the side where the female passed the winter, dis- ti:ictly swollen at the base. The starting of the gall must therefore be attributed to the female rather than to the nymphs. It is reasonable to suppose, however, that the nymphs settling in the partially formed gall have some influence on its further dtvelopnicnt. All of our observations lead us to agree with this statement. In the case of a developing bud, at the base of which one or more females are situated with their beaks inserted in the tissues, we find more or less of the outer leaves of the bud enlarged and deformed even before the eggs hatch. The bases of these afifected leaves are wider and thicker than the normal leaves. As the nymphs appear and crawl in between the bases of the leaves and insert their beaks into the tissues of the leaves, the irritation and stimula- tion are maintained and increased and the basal part of the affected leaves enlarges rapidly until a characteristic gall is formed. A normal bud, when it starts in the spring, is larger in diameter at the tip than at the base. On the contrary, a bud at the base of which one or more female aphids are hibernating, is as large in diameter at the base, and more often larger, than at the tip, when it begins to grow. The aphid unquestionably imparts to the leaves of the bud a stimulation that begins the formation of the gall. The newly hatched nymphs are fairly active, and crawl up the young shoot which is now growing rapidly. They soon seek the spaces behind the modified leaves and crawl down among the bases of them. The modifi- cation of the leaves is apparently accelerated by the influence of the nymphs, for each leaf covering the aphids enlarges at the basal part while the distal part remains of normal size. Since the basal parts of many leaves become enlarged, a bulbous or gall-like enlargement of the whole The Spruce Gall-Aphid 11 growing- branch is formed and the branch itself is checked in growth. If the aphids are abundant enough to occupy spaces between all of the leaves, then the gall is formed the whole way around the branch (see cover illustra- tion). If the aphids are few, the enlargement may take place on one side only of the growing branch. In such an event the branch is usually bent in the direction of the side on which the half-gall is formed. In some cases the gall so completely involves the whole bud that the growth of the branch is entirely checked. In most cases, however, the branch grows more or less beyond the gall, although never probably to what its full normal length would have been if no gall had been formed. Since the galls are deforma- tions of the branch buds, they are always at the bases of branches. The gall is more or less elongated, about 1 inch long, and shaped much like a pineapple, the sharp distal ends of the leaves answering to the spines and thus increasing the resemblance. The name pineapple gall is a very appropriate one. The gall is of a beautiful green color, somewhat yellowish at first but becoming deeper green later. After it has completely formed, reddish pubescent lines appear along the lines of junction of the leaves, and these add to its attractive coloration. The cells of the gall may be from 40 to 50 or even more in number, and each cell, containing from eight to twelve nymphs, is entirely closed. The red lines disappear as the gall grows older, and before the gall opens it turns yellowish in color as though it were ripening. During the latter half of August the leaves begin to separate and openings are formed leading to the cavities in which the aphids are situated. Through these openings the fourth-stage nymphs emerge, and the galls quickly turn dark and dry and harden ; but they remain on the branches indefinitely, giving the trees an untidy appearance. Developmcjit of the nymphs in the galls Several nymphs are ensconced in the cavity behind each leaf, and their development can be traced by opening the galls at varying intervals during their growth. In 1923 the first nymphs to molt were found on June 4, and by June 7 many nymphs in their second instar were noted. On June 18 the tirst third-instar nymphs were observed, but most of the nymphs were still in the second instar. By July 2 most of the nymphs had transformed to the third instar, and on July 13 the first fourth-instar nymph was found. The fourth-instar nymphs are the so-called pupae, for in this stage the wing-pads are developed and are conspicuous. By August 9 most of the aphids had progressed to the fourth instar, and on August 15 the first winged adults were observed. By August 26 to 29, many of the pupae had emerged from the galls and had transformed to winged adults. It was not, however, until from September 5 to 10 that the majority of the galls vv^ere open. The first eggs of the winged females were found on August 22. They were laid beneath the body of the female, on the leaf, to the number of 40 to 50. Many females were depositing eggs by September 11, and the first nymphs to hatch were discovered on that date. Many nymphs were pres- ent by September 29. Emergence and habits of the winged female When the diflFerent cells in the gall open in August, the pupae (fourth- instar nymphs) crawl out of the openings and settle on the leaves. In from 12 Bulletin 454 two to three days the nymphs molt and transform to the winged adult oviparous females. These females are certainly very inactive, and in the great majority of cases do not move far from the places in which the respective nymphs have cast their skins. The writers have never seen any indications of a migratory movement among these females. One wonders how this insect spreads from one plant to another, for it certainly does do so although the dispersal from a common center is gradual and very slow. The females settle rather quickly after the body has hardened, and, for the most part, go to the undersides of the branches. In from two to five days each one begins laying its quota of eggs, and the egg-laying continues for about ten days, when the full number, from 40 to 50, have been laid. The female dies when her eggs are all deposited, but her dead body covers the eggs and clings to the leaves long after the young nymphs have settled for the winter. Indeed, the shriveled bodies of the females may be found late in the winter. The eggs, which begin to be deposited during the first week of September, hatch through a period of two weeks, so that some of them do not hatch until the latter part of the month and probably some not until into October. The young nymphs are active, and crawl about over the leaves appar- ently inserting their beaks now and then to feed. By the latter part of October most of the nymphs have migrated from the leaves to the twigs and have settled for the winter. They insert their beaks into the tender bark of the twigs, and many of them secrete waxy threads over their bodies. The nymphs tend to gather in groups mostly near the distal ends of the twigs, where they may be found during the winter. Suiiiniory of life history The insects overwinter as small nymphs of the ovipa- rous, wingless, agamic females ensconced in crevices about the bases of the buds. In the spring these nymphs rapidly mature, and in May each adult lays from 150 to 200 or more greenish yellow eggs in clusters beneath her body (figure 4). These eggs hatch in about one week, and the young nymphs crawl down behind the already enlarged bases of the leaves of the spruce buds. The presence of the nymphs causes the leaves to enlarge further and the branch to become Figure 4. an overwintering female just checked in its growth, thus BEGINNING TO LAY EGGS, MAY 22 formiiig a large gall re- The insect is covered with white waxy threads SCmbling a ITliniatUrC pine- The Spruce Gall-Aphid U apple. The nymphs soon become entirely inclosed in the gall, and remain so until August. In the latter half of August (in New York) the galls open, and the nymphs crawl out of their cells, molt, and transform to winged, agamic, oviparous females. These females remain on the spruce, and in August and September each lays a cluster of from 40 to 50 eggs on the leaves. The eggs hatch in about one week, and the nymphs soon settle down in crevices about the buds, there to pass the winter. Thus the life cycle is completed, there being two parthenogenetic generations on the spruce each year. PARTHENOGENETIC DEVELOPMENT The species of the genus Chermes have been investigated with great detail in Europe through a period of many years, and considerable controversy has arisen regarding the life history and biology of the species Adelges (Clwniics) abietis. Blochmann (1890) published a paper in which he held that Chermes abietis had an alternate or intermediate host plant, the larch tree. This immediately aroused the curiosity of Cholodkovsky as to how the insect lived in northern Europe, where the larch is not present. As a result of Cholodkovsky's careful and extended study (1910, 1911. 1915), he believed that there were two species of Chermes: one which he called Chcniies abietis Kalt., and which passed through a cycle of two generations and lived permanently and parthenogenetically on the spruce ; and another which he called Chermes viridis Ratz., with a cycle of five gen- erations (one sexual) and living on both the spruce and the larch, the latter tree being the intermediate host. The accompanying diagram (figure 5) shows graphically the life cycle of these two species in Europe according to Cholodkovsky. Borner (1908, a and b), adopting the "parallel-row theory " of Dreyfus (1890). maintains that Chermes abietis develops two 6exuales(§^ Fundatrix vera Alata nor) migrans Fundatrix spuria Fundatrix Migrans alata Figure 5. graphical representation of the life history of chermes viridis (a) and of chermes abietis (b), according to cholodkovsky (after steven) 14 Bulletin 454 races or strains or branches as it were, one of which lives on the spruce while the other migrates to the larch and passes through a complex cycle on that plant. In other words, he claims that the sexes (Sexuales) give rise to the hibernating nymphs (Fundatrix) which ma- ture in the spring and lay the eggs that produce the gall-making forms (Fundatrigenia), part of which, when they mature, remain on the spruce and part of which migrate to the larch, thus living in parallel rows, as it were, on the spruce and the larch at the same time. Borner therefore holds that there is but one species of this form Chermcs abietis, and that the parthenogenetic form of Cholodkovsky does not exist as a distinct species. Our investigations in the vicinity of Ithaca do not show any sexual forms of this aphid. We have not found any evidence that there is a specific or varietal form or race that lives on the larch, there developing a sexual cycle. We should not like to say that further careful investigation might not disclose such a form. It is a problem that we hope to investigate at greater length. It is of interest in this connection to note that Miss Patch (1909) finds no evidence of Adclges abietis going to the larch. She says : "A different species of host plant is never sought by this Clicrmes." Steven (1918) finds that in Scotland there are two separate cycles of the Chermes under consideration. One is a cycle of two parthenogenetic generations on the spruce, as we have found in Ithaca. This Steven calls Chermes abietis Kalt. of Cholodkovsky. He finds also a Chermes with a cycle of five generations, which passes one phase of its life history on the spruce and one phase on the larch. This, he believes, corresponds to Chermes viridis Ratz. of Cholodkovsky. This species or race we have not as yet found at Ithaca. CONTROL The senior author has been spraying Norway spruces for some years with diflferent materials in an endeavor to control the spruce gall-aphid. Most of these trials have been isolated attempts to control the insect on two or three trees, but in the spring of 1924 an opportunity was ofifered to make a test on a larger scale. The results (H^rrick, 1925) corroborated those of the earlier isolated sprayings and were very satisfactory. A hedge of Norway spruce trees about five feet high, which runs along one end and about half the length of one side of the grounds of Prudence Risley Hall at Cornell University, has been abundantly infested with the gall-aphid, and the infestation has been gradually increasing until some of the young trees have nearly succumbed to the injuries inflicted by the insect. This hedge, which has a total length of about 550 feet, offered a fine oppor- tunity for trying some control measures. On April 9, 1924, the hedge was thoroughly sprayed with powdered lime-sulfur at the rate of 16^ pounds to 50 gallons of water. The trees were sprayed from both sides, and care was taken to coat the branches thoroughly with the liquid. The senior author had this hedge under ob- servation throughout the season, and was not able to find a single develop- ing fresh gall. The caretaker of the grounds, who is interested in the problem and aided in the spraying, pruned the hedge in July, and, while doing so, kept a sharp lookout for galls. He failed to find a single one, The Spruce Gall-Aphid 15 and, since he pruned each tree in a rather careful manner, it is Hkely that he would have seen galls if any had been present. The senior author has along the front border of his own grounds a hedge of Norway spruce the trees of which are about five feet high. These small trees also have been se-^erely infected with the gall-aphid. On April 21, 1924, this hedge, which is about 75 feet long, was sprayed with Sunoco oil at the rate of 1 part to 20 parts of water. Warm water was used and the oil emulsified readily, forming a very satisfactory milky emulsion. The hedge was sprayed from both sides in a very thorough manner with an abundance of the liquid. During the summer, frequent examinations were made of the trees in search of developing galls. The writer was un- able to find any signs of the presence of the aphids and no fresh galls were discovered. It should be remarked that rain began to fall at about three o'clock in the afternoon of the day on which the trees were sprayed, and a drizzle continued through most of the afternoon. On an individual tree of larger size, sprayed on April 5 with Sunoco oil at the rate of 1 gallon to 15 gallons of water, five freshly developing galls were found, one on June 10 at the tip end of a side branch, and four at the topmost end of the leader. Unquestionably the tip ends of these branches were left untouched by the oil. The lower branches of this tree were cov- ered with old galls and the hibernating nymphs were abundant on nearly all of the branches at the time of spraying. No new galls, other than those mentioned, appeared on the tree. All of the trees sprayed with oil were watched during the summer and fall for possible signs of injury, but no evidence of the slightest ill efifect was observed until early in the following March, nearly a year after the application. Then it was noted that the snow underneath the trees was covered with spruce leaves, and on examination it was found that there appeared to be an abnormal shedding of the foliage. The ends of the branches of nearly all the young trees in the hedgerow were bare of leaves, making the efifect very noticeable. The defoliation did not seem to be progressive, and did not appear to be serious although it did give the hedge a somewhat unthrifty and untidy appearance. Indeed, one cannot be positive that the effect was due to the oil, although there was no evidence of abnormal shedding of foliage on unsprayed spruce trees, many of which were examined. Later, on July 25, 1925, the trees were in ex- cellent condition and the hedge showed no injury. On November 10, 1925, the hedge was in a perfectly normal condition. In the spring of 1925 the attention of the writer was called to two Norway spruces about twenty feet high that were literally covered with the galls of this aphid. The trees had made little growth during the pre- ceding year, and looked ragged and unhealthy. They were two among a half dozen fine trees standing in a row and close together. All of the trees had been making excellent growth, but these two, standing at the end of the row, had become infested, probably from two other infested trees some distance beyond them. On April 6 these trees were sprayed with Scalecide, 1 quart to 20 quarts of water. The oil was fresh and emulsified very satisfactorily. The trees were sprayed very thoroughly and every part of them was covered. The weather during the next few days was propitious, and the oil had a 16 Bulletin 454 chance to do its work. April 7, 8, 9, and 10 were fine days without rain but with rather heavy frosts during the nights. The results of this spraying with Scalecide seemed, up to November 10, to have been very satisfactory. Observations of the trees during the sum- mer and fall failed to disclose a single new gafl. All of the evidence indi- cated that this miscible oil is nearly a specific in destroying the spruce gall-aphid. There was no evidence of any injury to the tree by the oil, when applied during the spring of the year at the dilution of 1 part to 20 parts of water. Britton (1924) says, regarding the control of this gall-aphid, that spruce trees have been efifectively sprayed for several years with miscible oil, at a dilution of 1 to 20, in the fall and in April, and that there has never been any injury to the trees except once, and that was probably due to the contents of the original package not having been thoroughly mixed before dilution with water. It seems apparent that oil emulsions, miscible oils, and lime-sulfur either dry or liquid, are effective materials for the control of the spruce gall-aphid. The senior author has obtained effec- tive results on a few trees at different times with the concentrated solution of lime-sulfur at winter strength, 1 gallon to 8 gallons of water, when the solution tested 32° Baume. The lime-sulfur may be somewhat objec- tionable because it tends to stain the foHage of spruce trees ; at least, it gives the trees a whitewashed appearance which may persist for some time and to which some owners might object. The oils do not produce any discoloration of the foliage, and if they do not produce marked injury to the trees, such as may prohibit their use on spruces, they are probably preferable. The Spruce Gall-Aphid 17 REFERENCES CITED Blochmann, F. Ueber die regelmassigen Wanderungen der Blattlause, speziell iiber den Generationszvklus von Chermes abietis L. Biol. Centbl. 9 (1889-90): 271-284. 1890. BoRNER, Carl. Systematik und Biologic der Chermiden. Zool. Anz. 32 (1907-08) : 413-428. 1908 a. tjber Chermesiden. II. Experimenteller Nachweis der Entste- hung diocischer aus monocischen Cellaren. Zool. Anz. 33 : 612-616. 1908 b. Brixton, W. E. Spruce gall aphid. In Twenty-third report of the State Entomologist of Connecticut, 1923. Connecticut (New Haven) Agr. Exp. Sta. Bui. 256:240-241. 1924. Cholodkovsky, N. Aphidologische Mitteilungen. 26. Zur Kenntnis der westeuropaischen Cherme s-Arten. Zool. Anz. 35 (1909-10) : 279- 284. 1910. Aphidologische Mitteilungen. 27. Uber Chermes abietis Kalt. und Ch. viridis Ratz. Zool. Anz. 37: 172-174. 1911. [Russian title.] Chermes injurious to conifers. (Abstract.) Rev. appl. ent., Ser. A (Agricultural), 3:592-599. 1915. CoMSTOCK, John Henry. An introduction to entomology, p. 1-1044. (Reference on p. 429^32.) 1924. CooLEY, R. A. The spruce gall-louse. Massachusetts Agr. Coll. Rept. 34:1-12. 1897. Dreyfus, L. Zu Prof. Blochmann's Aufsatz, " Ueber die regelmassigen Wanderungen der Blattlause, speziell iiber den Generationszyklus von Chermes abietis." Biol. Centbl. 9 (1889-90) : 363-376. 1890. Gillette, C. P. Chermes of Colorado conifers. Acad. Nat. Sci. Phila- delphia. Proc. 59 : 3-22. 1907-08. Herrick, Glenn W. Methods of control for two shade-tree pests. Journ. econ. ent. 18 : 630-632. 1925. Patch, Edith M. Chermes abietis Choi. In Chermes of Maine conifers. Maine Agr. Exp. Sta. Bui. 173:290-294. 1909. Steven, H. M. Contributions to the knowledge of the family Cher- mesidae. No. I : The biology of the Chermes of spruce and larch and their relation to forestry. Roy. Soc. Edinburgh. Proc. 37 (1916-17) : 356-381. 1918. CIRCULAR No. 64. United States Department of Agriculture, BUREAU OF ENTOMOLOGY, L. O. HOWARD. EntomoloEist. THE COTTOxNY MAPLE SCALE. (Pulvinaria innumerabilis Rathvon.) By J. G. Sanders, Assistant. The cottony maple scale {Pulvinaria innunicrahilis Rathv.) at ma- turit}' is the most conspicuous scale insect indigenous to the United States, and has received much attention from entomologists and horti- culturists on account of its occasional abundance. It was described in 1854 by Dr. S. S. Rath- von, of Lancaster, Pa., Avho gave the pest a very expressive and significant specific name. Since then over 60 articles and references concerning this species have appeared in entomological literature, besides hosts of others in newspapers and other periodicals. Of special worth is a monograph of the species, worked out in elaborate form by J. D. Putnam, which was pub- lished in the Proceedings of the Davenport (Iowa) Academy of Natural Sciences, p. 339 (1S79). More recently in Bulletin 22, new series. Division of Entomology, Dr.L.O. Howard published a thorough treatise on "The Two Most Abundant Piilvinarias on Maple," giving in detail the distribution, food plants, and life history of the cottony maple scale and the nearly related maple- leaf scale, illustrated by numerous figures of the various stages of each species. Sporadic outbreaks of this scale insect in various parts of the United States have been reported from time to time for many years past, but in each case natural enemies have subsequently increased with suflicient rapidity to effectually check its progress. Recently many reports of its extreme abundance have come to us from the city of Chicago and Fio. l.—Ptdijinariaiimviturahilis: adult ft'iiialos in tiosition on twigs, with egg sacs— natural size (from Howard). vicinity, and from various sections of Illinois, Indiana, Wisconsin, and Iowa. It is interesting to note that most of the reports of serious injury by this insect come from those States or portions of States north of the fortieth parallel, where it seems to be attacked by fewer parasites than in the southern regions. A map of its distribution prepared by the author from locality cards shows that it is distinctively an Upper Austral zone species but occasionally reaches the Transition zone. The cottony maple scale is classified in the soft, unarmored group (Non-Diaspinse) of the family Coccida?, and does not differ superficiallj' from the Lecaniums, except in the formation of an ovisac by the female of the Pulvinaria. The male insect is a veiy small and delicate two- winged fly which develops its latter stage under a glassy test or covering and emerges late in August or early in September. FOOD PLANTS. The various species of maples, particularly the soft maple {Acer saccharinum) , including the box-elder {Acer negiindo), are the favorite food plants of this species. The writer has, however, found it on 47 different species of trees, shrubs, and vines, including various species of maple, oak, linden, elm, willow, poplar, beech, hawthorn, sycamore, locust, hackberry, osage-orange, mulberry, grape, poison-ivy, apple, pear, plum, peach, currant, gooseberry, rose, and Virginia creeper. It is possible that a very careful study will prove that all these infestations are not referable to one species, but that other species may be separated just as the maple-leaf Pulvinaria [P. acericola (Walsh and RilejO] and the osage-orange Pulvinaria [P. maciuree (" Kenn.," Fitch)], once con- sidered identical, were found to be distinct from the cottony maple scale. Habits and life history. The large, white, iiocculent masses, resembling popcorn fastened to the twigs, which appear on infested trees during the month of June, are the cottony (really' waxy) ovisacs of the female, provided for the retention of the eggs after oviposition (fig. 1). These may contain as many as 1,500 minute, oval, pale reddish-yellow eggs. The larvse hatch at various dates from June 1 to August 15, depend- ing on the latitude and exposure to the sun's rays. After remaining in the ovisac for a day or two, they swarm over the twigs, instinctively migrating toward the light, and settle on the leaves along the midribs and veins, always preferring the under surface (tig. 2, e) . The larva? on box-elder become active somewhat in advance of those on maple. This difference may be due to the food, but it must be remembered that the shade of the box-elder is less dense than that of the maple, and consequently the greater amount of heat and light may be the con- trolling factor. The male larva;>, when fully grown, assume a propupal stage from which they pass to the true pupal stage having a pinkish hue. In a few days the winged males appear, but remain beneath the scale for two or three days before emerging. The females at this time have a few dorsal brownish markings and have undergone two molts. The males and females copulate in September, and soon afterward a small proportion of the females migrate to the twigs, where they insert their probosces and become fixed for the remainder of their existence, meanwhile changing from a greenish color to buff and finally brown, with a slightly tessellated waxy covering. In this condition the winter is passed (fig. 3). When the sap begins to flow in the early spring the female grows rapidly, mainl}' because of the rapid development of great numbers of ^^fi$?^\^ ^' Ftn. 2.— Pulm'nfiria innumerabiUs: a, newly-hatched young: t, female, third stage, from above; c. same, from side; d, male, third stage; e, same, natural size, on leaf and petiole; f. same, en- larged, on leaf petiole showing two specimens parasitized— all greatly enlarged except e (from Howard). eggs within the body. In May or early June the ovisac begins to form from the fine waxj^ threads exuded from the posterior spinnerets, push- ing backward and upward until the bodj' of the female is almost vertical to the twig. Meanwhile the ovisac is gradually being filled with eggs, which hatch and undergo all the changes mentioned above. Thus, fortunately, there is but a single brood each year. PARASITES AND PREDACEOUS ENEMIES. Notwithstanding the extreme prolificacj^ of this insect, it is usually held in check by its many natural enemies. Doctor Howard has observed the English sparrow apparently feeding upon the full-grown scales. The twice-stabbed ladybird {Chilocorus Mvulnerus Muls.) is a common enemy of this as of other scale insects, particularly in its early stages. The smaller similarly marked Hyperaspis binotafa Say (fig. 4) and H. signaia Melsh. are also valuable enemies of this species. The writer found in the severely infested parks and cemeteries in Chicago that the egg-contents of 80 to 85 per cent of the cotton}' ovisacs had been destroyed by the white mealy larvse of Hyperaspis. These larvte enter and devour the entire contents of one ovisac after another without destroying its form, so that onlj' an examination will reveal the empty ones. The predaceous caterpillar of IxefUia cocciclii'ora Comst. has been an efficient ally in controlling the pest in the vicinity of Washington, D. C. It is particularly effective where the cottony masses are in close prox- imit3% because of its habit of eating its way through the masses, spin- ning a strong web about itself, and forming a gallery as it progresses. The caterpillar is very active and moves about freely within its web. Several specimens of Leucopis nigricornis Egger, a common dipterous parasite of aphides, were reared from cottony maple scale collected in Chicago, 111., on July 21, 1905, by the writer, and from other specimens sent to the Bureau from Crystal Lake, 111. This parasite is considered to be a European species, and although aphides seem to be its favorite host, it is occasionally reared from nondiaspine Coccidae. Several species of chalcid flies (Chalcidoidea) are trulj^ parasitic upon the cottonj' maple scale as well as upon others of the Lecaniina?. There is no doubt that many more Pulvinarias are killed by these interesting little fellows than b}- all other enemies. Coccophagus lecanii Fitch, C. flavoscn- tellum Ashm., Atropates colUnsi How., Aphycns pulvhiarue How., Comys fusca How., and Eimoins lividus Ashm. have been reared from the cottonj' maple scale. REMEDIES. Fig. Z.—Pxilvinaria innn- merabilis: gravid fe- male, greatly enlarged, before commeneing to secrete egg sac in tlie spring (from Howard). In dealing with an infestation by the cottony maple scale, the most important matter to be considered in each case is the advisabilit}^ of artificial means of control under the existing conditions. The natural enemies of this pest have done and are still doing such effective work in its control, that it is a question whether remedies should be applied when the infestation is not serious. Nature always maintains a balance, and this pest can not be in the ascendency for any great length of time. On the contrary its parasites will eventuallj^ multiply so rapidly as to completely check its progress, and it may even narrowly escape extermination. Insecticides applied for a pest alwaj'S kill its parasites and often- times predaceous enemies are also destro3^ed. Hundreds of larvae of Hyperaspis hinofata were found to have been destroyed by a summer treatment with kerosene emulsion for the cottonj' maple scale in parks i^c of Chicago, and no doubt thousands of the minute ehalcids were killed, as the}' were found quite plentifull}' on unsprayed trees. If it is necessary to resort to artificial means of control, as seems to be the case in some sections, the spraying should be delayed until fall or winter, when the Hyperaspis is hibernating at the bases of the trees among lichens, moss or dried grass. Care should be exercised in the use of spraj', and the bases of trees should be covered with canvas or other suitable material to prevent the spray from running down the tree- trunks and collecting at their bases. WINTER TREATMENT. When the trees have become dormant, after the falling of the leaves, they can be trimmed and thoroughlj- sprayed with a strong kerosene emul- sion, which will kill ever}' scale reached b}' the spra3% without injury to the trees. Scarcely one-fourth the quantitj'^ of emulsion is required to spray a tree in winter condition that is necessarj' when a tree is covered with dense foliage and both sides of the leaves must be reached with the spray. Some excellent results have been obtained by Mr. S. Arthur Johnson ^ in experiments against this pest in Denver, Colo. He found that kerosene emulsion 25 per cent or more in strength or whale-oil soap at the rate of 1 pound to 1 gallon of water was very effective, apparentl}' killing all scales which received the spra3^ SUMMER TREATMENT. Kerosene emulsion of not more than 10 to 12 per cent of oil can be thoroughly applied with safety to maple trees, but the tips and margins of the leaves may be injured even at this strength. Box-elder will be almost defoliated with a 12 to 15 per cent solution. Less than a 10 per cent emulsion will be of little value against the young unless they have recently hatched. Since the hatching period may extend over six or eight weeks, it will be seen that more than one spraying will be neces- sary' to insure success, and, coupled with the fact that it is a very difh- cult and disagreeable task to thoroughly spray a tree in foliage, the winter treatment will be found more satisfactory^ in ever}' way. And at that season the larvae of predaceous beetles would not be destro^'^ed. Pig. i.—Hyprraspis binotatu: a, adult; 6. antenna: <■, palpus; y Mr. R. A. St. George, scientific assistant, Forest In- sect Investigations, Bureau of Entomology. Bui. 787, U. S. Dept. of Agriculture. Plate I. 5?;^ - M- Fig. I.— Natural Growth of Locust in an Old Abandoned Field of Some 60 Acres in Extent at Falls Church, Va. Trees badly infested by the locust borer. Several killed and others blown over. Note scattered position. Diameter near base, 2 to 6 inches. Fig. 2.— Natural Growth of Locust in an Old Abandoned Field of Some 60 Acres in Extent at Falls Church, Va. Several old seed trees and surrounding root sprouts and seedlings. Note thick growth. None of these trees are infested. Diameter near base, 1 to 8 inches. PROTECTION FROM THE LOCUST BORER. Bui. 787, U. S. Dept. of Agriculture. Plate 1 1 . Fig. I. —Natural Growth of Locust in an Old Abandoned Field of Some 60 Acres in Extent at Falls Church. Va. An isolated clump of some 30 trees, 2 to 4 inches in diameter. These were growing close together and mixed with taU weeds and sassafras bushes. Illustration after clearing the trunks in July when not a single borer was present. In September these were hea\-ily infested. Fig. 2.-ILLUSTRATI0N OF A FENCE RoW AT FALLS ChURCH, VA., SHOWING Thick Locust Growth of 2 to 5 Inches in Diameter near Base. None of these trees contained borers in July, 1918, when the underbrush and small branches were cleared from the trees in the foreground. These trees were infested in September. PROTECTION FROM THE LOCUST BORER. Bui. 787, U. S. Dept. of Agriculture. Plate III, Fig. I.— a Dense Growth of Root Suckers from a Few Old Trees that Were Removed, on Miners Hill near Falls Church, Va. This illustrates the type of prowth that will not be attacked. In the background to the right of the road are many trees containing 5 to 20 borers each. It illustrates the pruned portion of example 1 (see p. 3). Fig. 2.— Large Matured Locusts at Vienna, Va., Showing What Can Be Grown in a Locality Where the Borers Are Very Abundant. These trees show no e\"idence of borer injury. PROTECTION FROM THE LOCUST BORER. PROTECTION FROM THE LOCUST BORER. 5 old waste land, the soil of which has been enriched by a thick bed of humus beneath the trees. Another group (PI. I, fig-. 2) near by contains about 30 trees similar in respect to size and conditions. These have seeded the surrounding soil so that a large clump is formed of dense growth, the outermost being some 6 to 8 feet high. None of these trees have been injured by the borer. A third group (PL II, fig. 1), forming a small oval clump, contains 38 trees from 2 to 4 inches in diameter and 15 feet high. They were closely set, averaging 4 feet apart. A few sassa- fras were intermixed. In July, 1918, not one of these trees tiontained a borer. August 20, 1918, the plot was thinned, all branches trimmed to 8 or 10 feet, and all weeds and briers removed. The trees were closel}^ watched and many adults were observed ovipositing on them during September.^ Adults were likewise observed on the isolated trees near by, but none in the dense plats described above. 6. A fence row opposite the eastern field station at Falls Church, Ya., is densely matted with wild cherry, honeysuckle, and goldenrod along the sides. Through this grow a dozen locusts (PI. II, fig. 2) 2 to 4 inches in diameter. None of these trees were infested on or previous to August 15, 1918, on which date all the surrounding growth was cleared from four trees. During September adults were observed ovipositing on these four. Many such fence rows exist wherever locust is grown and explain why so little trouble is experi- enced on the average farm. 7. Along the south bank of the Potomac River between Difficult Eun and Scotts Run many locusts are growing on the wooded slope. This stand is a hardwood mixture composed chiefly of oak, chest- nut, hickorj", tulip tree, basswood, and butternut. All the locusts are tall, straight poles, reaching to the top of the stand, the trees averaging from 6 to 18 inches in diameter. All show a thrift}^ condi- tion of growth and no borer defects. A low meadow, sometimes cul- tivated but now pastured, lies between this river terrace and the water. A few occasional locusts grow here, nearly all of which are infested and badly deformed. No goldenrod occurs in the meadow, and the adult beetles were observed to feed on several species of Eupatorium. PLANTATIONS ALONG THE PENNSYLVANIA RAILROAD. From the office of the forester of the Pennsylvania Railroad rec- ords have been secured of 42 plantations, comprising nearly 2,000 acres, on which over 1.000,000 trees were planted. These trees were about 2 years old when set out and usually were spaced 8 by 8 or 8 by 10 feet. Many of these tracts were personally examined by the writer, accompanied by Mr. I. T. Worthle}', assistant forester. The history of each plantation was ascertained as accurately as possible. 1 Examination of this plot on Apr. 8, 1919, showed an average of 15 borers per tree. 6 BULLETIN 787, TJ. S. DEPARTMENT OF AGRICULTURE. Some of these tracts are in excellent condition, others almost totally destroyed. It is necessary to describe only a sufficient number of these to give all conditions of culture and past history. 8. Along the line of the railroad, between Philadelphia and Har- risburg. Pa., near Kinzers, are two locust plantations, one on the south side planted in 1904, one on the north planted in 1905. To- gether they comprise about 25 acres, containing 44,000 trees. As far as can be ascertained, nothing was done in these plots until 1909 and 1910, when thorough prunings took place. The entire tracts were gone over and all the trees trimmed to a single straight stem. All natural growth of other trees or shrubs was thinned out. The writer personally assisted in one of these thinnings in 1910 and at that time noted a few borers in the larger trees. Nothing more was done, but an examination in 1912 showed the borer very abundant and many trees breaking off. At present it is difficult to find a good tree. A few have not been injured sufficiently to cause them to break, but the great majority form a broken tangle. Many root sprouts and suckers are present. These are now meeting the same fate. 9. Near New Brunswick, at Stelton, N. J., are several more plan- tations in a long strip on the old roadbed comprising some 8 or 10 acres of 13,000 trees. One of these lies along the present roadbed near the station. These trees have been pruned from time to time by the section crews. At present they are badly infested (in the spring of 1918 averaging 10 living borers to a tree) but few broke off until the summer of 1918, when a severe wind destroyed about 5 per cent. These trees average 2 to 5 inches in diameter. Farther west, some distance from the present roadbed, is a simi- lar stand planted at the same time. No care was taken of it and the trees grew up in thick weeds and other natural, shrubby growth. They are scarcely close enough to produce much natural pruning and all have several large branches. An examination in 191T and 1918 showed that only a very few trees were infested or ever had been infested. The average diameter is larger than that of those nearer the station. 10. One mile east of Metuchen, N. J., are 10,000 trees planted in 1909, divided into about equal stands, one on the south and one on the north side of the roadbed. The north plot was pruned at two different times, but the years could not be determined. In the spring of 1918 all these trees were badly infested and many were broken off. Many root sprouts and suckers have grown out. The trees on the south side never were pruned or thinned. In the spring of 1918 it was almost impossible to find a borer in the tract ; however, a certain amount of old work was present, though not sufficient to mar the trees greatly. These trees were not planted close enough to cause natural pruning and consequently are considerably branched. Very PROTECTION" FROM THE LOCUST BORER. 7 few root sprouts occur in this tract. Tliey are now producing a more dense shade and natural pruning is taking place. At an earlier date, when the trees were less dense, borers attacked, but as the density- increased they probably Avere repelled before the trees were seriously injured. The diameter of the stand on the south side averages several inches more than that of the standing trees on the north side. If these trees on the south side had been planted several feet closer, say 6 by 6 in- steacl of 8 by 10 feet, it is the writer's opinion that they would now have unbranched stems with practically no borer defects. 11. On the low-grade freight line between Martic Forge and Co- lumbia, Pa., are five plantations set out in 1906 containing about 150,000 trees. None of these have ever received any attention in the wa}' of pruning. The}" present conditions varying from such as described at Kinzers (example 8) to almost perfect stands free from borer injury. In no single plantation are the trees all destroyed or all in good condition, but the extremes are found in different parts of each tract. Another factor has been responsible here. A definite correlation exists betAveen those parts of the plantation that have been run over by fire and those parts which were by nature of their posi- tion less subject to fire. Where fire has burned over repeatedly, kill- ing the undergTowth. the worst destruction by borers is found. In many places the locusts themselves have been killed. One tract near Shenks Ferry attracted particular attention. It extends from the roadbed across a bottom and up over a hillside. Fire no doubt has gone through the part near the tracks repeatedly, as evidenced by the different ages of scars on the standing trees. Here there is little undergrowth; the locusts are scattered (many ha^e been fire-killed), and all are severety infested. On the hillside and over the crest, fires, for some reason, have not gone through. The locusts have grown up in a dense stand mixed with much underbrush, and oak and chestnut sprouts from the original stumpage. These trees are now in excel- lent condition ; the}' are tall, straight, thrifty, not branched, and free from borer defects. In some parts the shade of the mixed stand has become so dense that all weeds, briers, and underbrush have been sliaded out. 12. Along the railroad between Harrisburg and Huntingdon, Pa., much locust has been planted, and man}' natural stands occur. The condition of the locust in this region is generally so much better and so much more thrifty that the first examination gave the impres- sion that it is an exceptionally favorable situation for the growth of the tree. It is no doubt true that certain localities are better adapted to the growth of black locust, but the essential factor in this location is considered to be more than purely a favorable situation. The locusts are growing in a narrow belt of river terrace from a few 8 BULLETIN" 787, U. S. DEPARTMENT OF AGRICULTURE. yards to a mile wide between the foot of tlie mountain and the Susquehanna and Juniata Eivers. There is much humidity, and all vegetation is vigorous. It is believed that the good condition of these locusts and the decided absence of injury by lx)rers are due to the fact that the situation is conducive to a rapid growth of underbrush and plants characteristic of river shores which have afforded protection to the locusts. This is further emphasized by the fact that in other localities are found trees of equal size and good appearance, as describecl at Shenks Ferry (example 11), of the same age. Also in the same locality we find trees deformed and aborted by borer injury, as de- scribed in the following paragraph. 13. Along the Juniata Eiver between Newport and Old Ferry, Pa., a continuous plantation of locust set out in 1904 extends for a distance of 2 miles. These trees, especially that part near Newport, show the best stand of all the plantations. After planting no atten- tion was given them until 1914, when they were thinned to afford a view of the river from the trains. At this time most of the stems had reached a sufficient size to be immune from borer attack. The trees nearest Newport now average 5 to 8 inches in diameter. The}' are straight, free from branches, and about as tall as the telegraph poles near by. The bark is ridged naturally, showing absence of borer injury in the past. Nothing definite as to how these trees grew in the period intervening between planting and first pruning could be ascertained, but from a study of many plots of all ages along the river it is certain that they were intermixed with a dense growth of other shrubs and weeds. Natural pruning and thinning have taken place to such an extent that few living branches are found below the crown, and man}- trees have been suppressed and killed. Farther back from the railroad, where no pruning at all was done, the dead, suppressed trees and shaded-out branches give a good idea as to how rapidly this process takes place in the tree. In this 2-mile strip of locusts the borers are serious in two places and have caused many trees to break off or have stunted the growth badly. In one of these places fire has gone through; the other was evidently pruned (as shown by scars) to afford a view of a pond just behind. These last trees were also isolated in the sense that the rows were only two trees deep. These trees average scarcely half the diameter of those in the better parts of the grove. CONDITION OF TREE NECESSARY FOR BORER ATTACK. All trees and all parts of the tree are not subject to attack by the borer to the same degree. Moderately rough bark seems to be an essential condition, since it provides the necessary crevices in which the adults deposit their eggs. PEOTECTIOlSr FROM THE LOCUST BORER. 9 Likewise, until they become ll to 2 inches in diameter at the base, trees are not subject to attack unless the bark is rough. On younger trees the borers are found concentrated at the base and near crotches. For some unknown reason trunks of trees reaching 5 to 6 inches in diameter and over (excepting old brood trees) rarely are found to contain borers. On such trees the larger branches frequently are infested, but such injury is seldom common enough to do much harm or even attract attention. It can be said, therefore, that protection from borer injury is necessary for only a comparatively short period during the tree's growth. Under good growing conditions this time should not exceed 10 years. In every locust grove that has borers present, certain trees will be found on which they have concentrated. These are called brood trees. The thick, irregularly barked, gnarled appearance and stunted growth will distinguish such individuals. They are often continu- ousl}' infested until they reach an old age, or 12 to 18 inches in diameter. HOW TO RECOGNIZE TREES CONTAINING NO BORER DEFECTS. The larval mine made by the locust borer destroys a certain amount of the growing tissue or cambium and makes a serious defect in the wood. This injury to the cambium accelerates growth to heal it over and produces a swollen or gnarly appearance. Many such defects give the entire stem a roughened, distorted shape. The bark is ir- regular and scaly. On the other hand, trees that have not been in- jured by the borer are characterized by very regidar bark, which is grooved longitudinall}^ between thick, dark ridges. With a little experience these features can be quickly recognized and until the tree reaches 10 to 12 inches in diameter it is possible to determine accurately whether the borer defect will be found in the wood. CHARACTER OF GROWTH OF UNINFESTED STANDS. Not only is the appearance of uninjm-ed individual trees charac- teristic but pure stands of such trees have a different appearance from those that are damaged. The tops of isolated natural stands have a domelike outline, the innermost trees growing taller and straighter, while root sprouts continuously coming up around the borders form smaller and younger trees which give additional pro- tection to those within. These younger trees are at first too small for infestation, and when they have reached a susceptible size are protected in their turn. The crowns are uniformly shaped and no branches project to break the contours. Planted stands, where the trees are of the same age, are uniform in height, the tops forming a flat outline. No large branches are found on the trunks, but many 10 BULLETIN" 787, U. S. DEPARTMENT OF AGRICULTURE. small, naturally pruned dead branches are seen and many trees are thinned out naturally as the others increase in size. Few root sprouts appear. Infested plantations are very irregular in outline; broken tops, trees of irregular size, and many root sprouts and suckers are characteristic indications of borer damage. CONDITIONS UNDER WHICH LOCUST CAN BE GROWN. From the historj^ of the foregoing tracts it is evident that black locust can be grown profitably under circumstances that require little care, or, in fact, better results are obtained without too much atten- tion. After comparing all the data available it seems that provision for sufficient shade during the period of growth subject to horer attach is all that is necessary in order that this tree may be grown successfully. This can be achieved by some system of close and mixed plant- ing. Experiments of such a character should be tried. In nature it is accomplished by close reproduction coming up around the seed tree, by root sprouts from older trees, or often by the mixture of other plants growing with the locusts. Weeds and vines often fomi the needed shade, as illustrated by trees in old fence rows. It is very essential that this shade be present after the trees reach 1^ to 2 inches in diameter, and that it be continued until they attain 5 or 6 inches. After this time thinning and pruning can be done with little or no subsequent injury by the borers. Close planting or thick growth of these trees also is necessary to produce straight, unbranched boles. Trees in the open are always much branched and rather crooked, but those grown in forests are tall, straight, and naturally pruned while the branchas are quite small. That difference in site or locality is not the influencing factor in the growing of uninjured trees is evident from the fact that in every locality examined it was possible to find examples of borer- free and destroyed trees growing 100 yards apart. It is also evident that goldenrod is not necessarily associated with greater damage by the borer, for in the same abandoned field, massed with this plant, were found plots of trees absolutely free from injury and near-by isolated trees badly infested. Again, localities where no goldenrod is growing may have borer- infested trees, the adults feeding on other composites, as illustrated by example 7. The idea has been advanced that the borers are more abundant in some localities than in others and that this will account for the difference in infestation. This difference can not be sustained, as the beetles are present everywhere within the natural range of this tree. Side by side we find stands of badly infested trees and trees contain- ing no borers. It is rather to be believed that in localities where locust PROTECTION FROM THE LOCUST BORER. 11 was planted the beetles present either remained in about the same nmnbers or increased enormously, according as the condition of the trees retarded or favored their increase. In no new locality where plantations were put out would there be enough beetles present to infest all the trees. Thej?^ only attack all the trees as they become sufficiently numerous. CONTROL. A METHOD OF HANDLING SEVERELY DAMAGED PLANTATIONS. Many locust plantations have been abandoned and all hope of ever reahzing any commercial product given up because of the severe devastation produced by the borers. Such tracts look hopeless with the greater percentage of the trees broken off or killed, but it is believed that they can be reclaimed after several seasons' care by virtue of the sprouting ability of this tree. It is recommended that all such plantations be gone over and the broken-down and infested trees removed and burned during the winter. Unless otherwise desired it would be necessary to cut out only the living infested trees, because no beetles will breed in the dead ones. Especial attention should be given to the seriously dam- aged or so-called brood trees. If the cutting out of the infested trees can be done early in November it is not necessary to destroy or burn the wood. The larvse require living wood for their early development and will not mature in dead material. This not only will reduce the numbers of the insects, but before the sprouts become large enough to be attacked a sufficiently dense stand will have been developed to provide natural protection, as illustrated in Plate III, fiffure 1. TREATMENT OF SHADE TREES. The locust is widely planted for ornamental and shade purposes. It is very desirable for such planting, because of its ability to suc- ceed well in a variety of soils and situations and its rapid growth and good form of crown in the open. We often hear complaints of serious injury by the borer to locust shade trees; this is because such trees are usually grown in isolated situations most favorable for attack. It has been found that the young borers can be killed readily by the use of an arsenical spray, applied to the bark when the new growth begins to open at the tips of the twigs in the spring. It is necessary to apply this mixture so thoroughly as to cover all parts of the trunk and reach every spot where a larva is working.^ A thorough application will probably be necessary only every two years unless there are badly infested trees near by which are not treated and form centers of reinfestation. As a rule, spraying will 1 The presence of a young borer can be determined by the oozing of sap and boring dust from a small hole through the bark. This hole is enlarged as the larva grows. 1/ Circular No. 97 Issued February G, 1908. United States Department of Agriculture, BUREAU OF ENTOMOLOGY, L. O. HOV/ARD, Entomologist and Chief of Bureau. THE BAGWORM. ( Thiiridopteryx ephemerirforiiiDi Haw.). By L. O. Howard and F. H. Chittenden. GENERAL APPEARANCE AND NATURE OF ATTACK. Shade trees, shrubs, and hedges, and in particular evergreens, are much subject to injury b}' a medium-sized caterpillar which has a curious habit of crawling about on the infested trees in a bag-like case, whence its common name of bagworm or basket worm. In the shelter of these cases the insects undergo all their transformations, after which the bags remain attached to the plants for some time and are conspic- uous objects on leafless trees and shrubs in late autumn and in winter. Like the tussock moth" and the fall webworm^ this species is preeminently a pest on the streets and in parks and private grounds of cities and towns and is even more subject to fluctuation in num- bers. It is, however, more limited in distribution and not found as a rule north of southern 'New York and the central portions of Pennsylvania and Ohio. South of these points it is in certain years very trou- blesome and the subject of much complaint. Such a year was 1907, when the bagworm attracted greater F'"^'- i— Bagworm ,, ^. ., ii i 1 £■ !• i XT {Thyridopteryx attention tiian any other tree deroliator. ^Numerous ephcmcnc/ormis). complaints were received of injuries in the region Natural size (af- mentioned, and especially from the States of New Jersey, Pennsylvania, Mainland, Virginia, West Virginia, Ohio, Indiana, and Illinois. The natural enemies of this insect (see p. 6) were comparatively scarce, and there is a strong possibility of a recur- rence of injuries in the years to come. The general appearance of the bagworm is shown in figure 1, which illustrates the caterpillar when nearly full grown, in its characteristic bag. When removed from its bag it looks as shown in figure 2, «, which represents the larva pt maturit}' . At this period in its develop- « Hemerocampa leucostigma S. & A. 22089°— Cir. 97—12 b Hyphantria cunea Dm. nient it may attain a lengtli of about three-fourths of an inch. The both' is soft in texture and dull lirownish or blackish, while the head and thoracic segments are horny and whitish, mottled with dark brown. ORIGINAL HOME AND PKEi^ENT DISTRIBUTION. The bagworm is unquestionably native to North America. It abounds in the Southern States, and its proper home— that is to say, the part of the country where it roaches its maximum — is in the Lower Austral life zone. It extends through a considerable portion of the Upper Austral zone, but there are indications that it has gradually spread into this t(M-ritory from more southern regions. " The shade trees of Baltimore, Washington, St. Louis, and other more southern cities are frequently defoliated by this insect. Northward it occurs ^-vOfV Fig. 2. — Bagworm( Thi/ridopter;/x ephemerseformis) : a. Full-grown larva: b. head of same-: c, mnlf pupa; (1, female pupa; e. adult female: /. aihilt male. All enlarged (from Howanl <. through New Jersey and at many points in Pennsylyania. including the cities of Harrisburg, Elliottsburg, AUentown. and Swarthmore. Farther west it has been found at Columbus. Marietta, South Salem, and other localities in Ohio, at several points in West Virginia, at Brooklyn, Ind.,in Pecatonica, Thompsonville. and Allendale. 111., and so on west to Oklahoma. Everywhere south of these localities, except in the immediate Oulf region, it abounds. In the East it is commonly found in New York City and Brooklyn, and at several points on Long Island. In the Hudson Ili\er Valley region it has been recorded by Felt at Yonkers and Mount Vernon, and has been collected at New a In the main the bagworm is one of those characteristic forms like the wheel-bua (^n7»s er/.s?o/?'^- L.), the Carolina mantis (Stdytnoinantix Carolina L. ), and the larger digger wasp {Sphechift specioms Dru.), true southern forms which are gradually extending their northward range by following the seacoast or valleys, or, if carried accidentally northward upon railroad trains, establishing themselves at points beyond their former habitat. [Cir. 97] [Cir. 97] Fk;. 8. — Arborvila- infesli-il l>y linsworuis. (Original.) 4 Haven, Conn., l)ut it is not known to be injurious in these localities. It has been sent to the Bureau of Entomology from Springtield, Mass., but probably does not breed there. FOOD PLANTS. The bagworm, although a very general feeder, displays a particular fondness for evergreens of all kinds and especially for arborvitw, hence it seems probable that one or the other of these was its original or normal food plant (fig. 3). The species becomes exceedingly abun- dant everv few 3'ears, and at such times it may be found on shade, orchard, and forest trees of nearl}^ all kinds. It is fond of the maples, particularlj^ the cut-leaved and silver maples, and the related box elder; also of the willows, poplars, and mulberry, less so of the elms, and apparently still less so of the oaks. It feeds more or less f reel\-, however, on most other trees and shrubs, and even on rhany low- growing semi-woody plants, such as elder, mallows (Hibiscus), and ragweed {Ambrosia trijida). Thus, in the absence of its choice food plants, it is able to subsist on the foliage of almost any of the plants of the character enumerated and which may be available, but it does not seem to liv^e on grasses and lierbaceous plants generally. HABITS AND LIFE HISTORY. The bagworm overwinters in the o^gg stage within the old female bags, and for this reason hand-picking in winter time is an efficacious remed3\ In the late spring the young hatch from the eggs, crawl out upon the twigs, make their way to the nearest leaf, and immediately begin to feed and to construct cases or bags for themselves. They spin a large amount of silk and attach to it, for additional strength and protection, bits of leaf or of twig, evidently attempting to disguise the nature of the case as well as to strengthen it. The larva is remarkably soft-bodied, except for its head and strong thoracic plates, and it is necessary that the soft abdomen should have some protection. The construction of the bag of an allied species was careful! 3' studied by H. G. Hubbard, and it is a very interesting performance. The 3^oung larva (tig. 4, a) cuts off with its jaws a small fragment of leaf which it places between its front legs, gradually forming a pile fastened loosely with silk. When the pile becomes a transverse tangle about as long as the body it is fastened at each end loosely to the surface upon which it rests ; then the caterpillar, after placing itself at right angles, dives under the mass, turning a complete somersault, so that it lies on its back, bound down by the fillet. It then twists around and stands upon its feet, having its neck under a sort of yoke (fig. 4, h). It makes the 3^oke into a complete collar, adding bits to each end until [Cir. 97] and these vary with tree upon the circle is complete. Then row after row of fragments is added until the case becomes a hollow cylinder (tig. 4, c). One end is then closed up and the inside lined with a tough coating of silk, the case being then extended upright and fastened at one end. When it is f ullj- completed the larva crawls away, with the case carried upright like IX cap on the upturned end of its body. In the illustration d shows a completed bag made by the young larva, tightly appressed to the flat surface, the larva being concealed within. Such bags may frequently be found on leaves, and are quite puzzling to the uninitiated until the larva pokes out its head and slowly walks off. As the caterpillar grows the case is constantly' enlarged, bits of twigs and any other small objects being used to ornament the outside, objects will the kind of which the caterpillar is feeding. While the larva is small it carries its case erect, but when it is larger the case hangs down (tig. 1). The larval skin is cast four times, and during the molting the mouth of the bag is kept closed with silk. There is a small opening in the extremity of the bag through which excre- ment and cast skins are pushed. The male bags are smaller than those of the females, reaching a length of about an inch, while those of the females are much larger. Toward the end of August, about Wash- ington, D. C, the larva completes its growth, attaches its bag firmly by a silken band to a twig, strengthens it inside with an additional layer of silk, and within this retreat, which now becomes its cocoon, transforms to pupa with its head downward. The pupal period lasts about three weeks, and then the imago emerges. The male chrysalis works its wa}' out of the lower opening, and the winged moth issues [Cir. 97] Fig. 4. — a, Newly hatched bagworm before making its ease; b, same just beginning ease; c, showing case nearly com- pleted; d, completed case, insect concealed within; e, larva after first molt. Highly magnified (original). through the cracking skin, leaving the chrysalis hanging from the bag, as shown at r-, figure 5. The chrysalis of the female does not push its way at all out of the bag, but the skin cracks and the female gradually works her way partly out, her head reaching the lower end of the bag, (fig. 5, d). The males fly about, seeking the bags of the females, and when one is found in which the head of the female is near the end, showing that she has emerged from her chrysalis skin, the male pushes his enormously protrusive and, in fact, telescopic genital apparatus up into the bag to the anal end of the female and fertilizes her. The female then works her way back into the chrysalis skin, gradually filling it with eggs until more than half of it is filled, scattering in among the eggs some of the sparse hairs from her body. Having done this she forces her shriveled body out of the open- ing, falls to the ground, and dies. The eggs re- main in this way until the following spring, when they hatch, as previously described. There is thus onl}- one generation annually. Note.— There is a possi- bility that the bags of this extremely common insect might be made commer- cially useful. Its silk, from a practical standpoint, has always been ignored, but it is firmer and stronger and more easily spun as carded silk than that of most other native silk cocoons. Fig. 5.— Bag\V(jrm at (a, 6, c) successive stages of growth, r, Male bag; d, female bag. Natural size (from Howard). NATURAL ENEMIES. Although apparently well protected from the attacks of birds by its tough case, the bagworm is somewhat extensively parasitized b}^ several forms of ichneumon and chalcis flies, most of them species which affect also similar tree-feeding caterpillars. Prominent among these is the common Pimpla inquisitor Say (fig. 6), which, however, more commonly parasitizes the tussock moth and tent caterpillars." The related P. conqulxltoi' 8ay is also a parasite of the bagworm and a third species of ichneumon, Allocota^Uevilteles) thyrldopterlgls Kiley (fig. 7), is usually the most abundant of all. Four or five individuals of this species commonly infest a single bagworm, spinning for them- selves white silken cocoons w^ithin the bag. rcir. 971 « Malacosonia spp. The species last mentioned was for nianj'^ years credited with being a primar}' parasite of tiie bagworm. although recent observations would indicate that it is a secondary parasite when infesting- other Fig. 6. — Pimpla inquisitor: Female, from side. Enlarged (from Howard). Fig. 7. — AUocota ( Hemiteles) thyridupterigis. Much enlarged (original). caterpillars. This might be explained by the hypothesis that this parasite oviposits only in cocoons or cases of firm texture, and there- fore can not be the primar}- parasite of an insect which is not provided with a case of that character. Fig. 8. — SpUochalcis marise. Mufli enlarged (after Riley) . Certain chalcis flies also breed in the bags of this insect. These include SpUochalcis laarise Riley (fig. 8), Chalcis ovata Say (fig. 9), and the common little Dihrachys houcheanus Ratz. (fig. 10). Thi.s last is a hyperparasite, in the case of the bag- worm probably secondary, and in the case of other caterpillars a [Cir. 97] Fig. 9. — Chalcis ovata: Adult. Enlarged (from Howard). 8 tertiaiy parasite. Habrocytus thyridojpterigis Ashm. (fig. 11) is assumed to be a tertiary parasite on Allocota tliyridoptei'igis Rile}', when the latter is a secondary parasite of the tussock moth, but may be secondary when breeding in the cases of the bagworm. REMEDIES. Fig. 10. — Dibrachys boucheamis: Adult female and antenna of male. Much enlarged (from Howard). When the bagworm occurs upon deciduous trees it can be controlled by hand-picking the bags in the winter, but when it affects evergreen trees it is practi- call}" impossible to apply this remedy with profit unless the plants are badly defoliated. There- fore for the treat- ment of evergreens spraying is a neces- sity. The methods of controlling shade- tree pests in cities and towns, as out- lined in Farmers' Bulletin No. 99,*^ on pages 25-29, are in part applicable to this species. This bulletin should be read by persons who have experienced trouble from the depredations of the bagworm. Collecting the hags. — -?• One of the most important remedies consists in gath- ering the bags with the contained insect by hand and either burning them or preserving them to lib- erate the useful parasites which have been previ- ously mentioned. This work may be facilitated by the use of a 12-foot pole pruner or similar appliance, and can be intrusted to those ordinarily unemployed, such as children and aged persons. Where the trees are ver}" tall it will be necessary to use a long ladder. For best results the cooperation of neighbors who are troubled with the same pest should be secured. a This publication may be had gratis on application to the Department of Agriculture. [Cir. 97] Fig. 11. -Habrocytus thyridopterigis. Howard). Greatly enlarged (from Very considerable immunity from future injury will result by care in the employment of this method. It is particularly useful where only a few trees are infested. The bags are such conspicuous objects on defoliated or Imre trees in winter that it is not at all difficult to detect them, but in cases where comparatively few insects are present on evergreen trees they are not so easily seen. Encouraging the parasites. — When many trees are infested it is advisable to keep the hand-picked bags for a considerable time in receptacles, such as barrels covered with netting, preferably of wire, so that the numerous beneficial parasites of the pest will be able to issue in the spring and assist in the control of the bagworm the fol- lowing year. One or two holes bored in the bottom of the barrel or box will prevent water from accumulating and drowning the insects. Where the bags can be placed in piles in an open space or inclosure distant from trees and free from disturbance, the young insects, having very limited powers of locomotion, will soon perish of starvation, as they will not be able to reach the trees or shrubs after they hatch. Spraying with arsenicals. — On evergreen, where the bags are more or less diflicult to find, hand-picking can not be advised. A striking instance of the f utilit}' of this method under such circumstances was given by Prof. C. V. Riley in his testimony at a conference on the gipsy moth in 1891. He said that he once tried to protect a cedar tree not more than 6 feet high, upon his own grounds at Washington, by hand-picking. He worked for two consecutive months picking off small bags from that tree, the progen}' of not more than two females. Almost daily he went to the tree and found fresh specimens which he had overlooked the day before. For evergreen trees, therefore, an arsenical spray is the best remedy. In connection with the story of his experience just related, Professor Ililey stated that he had abso- lutely stopped injury by the bagworm on large trees in the Smith- sonian grounds by spraying, and in the summer of 1895 we had a similar experience on the grounds of the Agricultural Department at Washington. Trees sprayed with Paris green at the rate of 1 pound to 150 gallons of water were completely rid of larvae of the bagworms. It is easier to reach the bagworms on evergreen than on large-leaved deciduous shade trees, such as maple and elm, but if carefully carried out spraying will result in the destruction of the bagworms, so that the collection of the bags in winter will not be necessary. Arsenate of lead at the rate of 1 pound of the prepared paste form to from 25 to 50 gallons of water will be found even more useful than the Paris green, as its greater adhesiveness renders it less likel}^ to be washed off by rains, which in some seasons frequently occur almost daily at the time when the larvse are beginning to work. fCir. 97] 10 The best time to apply the arsenical is Avhen the eggs hatch, or shortly afterwards, and the best methods of spraying shade trees are discussed in Farmers' Bulletin No. 99. Approved: James Wilson, Secretary of Agriculture. Washington, D. C, Decemher ^, 1907. [Cir. 97] o THE PERIODIC Avidespread devastations of the southern pine beetle have been responsible for the destruction of more merchantable pine timber in the Southern States than has any other agency. During a single epidemic it has destroyed timber valued at $2,000,000, and the present stumpage value of pine killed since 1891 is placed at no less than $50,000,000. This tiny beetle kills healthy, vigorous pines of practically all ages and of all species which occur within its range. To do this, it attacks the middle to upper portions of trees and destroys the soft inner bark through which the trees get their nourishment. Recent investigations indicate that weather con- ditions have much to do with the abundance and destructiveness or the scarcity of this beetle. Ab- normally dry weather seems to be followed by out- breaks, but when the drought is broken by normal or heavy rainfall the beetle may almost disappear. Low winter temperatures also effectively check these beetle outbreaks. This bulletin describes the insect and its work, its life and habits, and the methods that have been employed to prevent and suppress outbreaks. It supersedes Farmers' Bulletin 1188, The Southern Pine Beetle: A Menace to the Pine Timber of the Southern States. Washington, D. C. Issued May, 1929 THE SOUTHERN PINE BEETLE: A SERIOUS ENEMY OF PINES IN THE SOUTH By R. A. St. Gemrgb, Associate Entomologixt, and J. A. Beal, Assistant Ento- mologist, Dimsion of Forest Insects, Bureau of Entomology CONTENTS Page Beetle outbreaI;s and their impor- tance 1 Evidence of beetle attack 3 The beetle : Its work and its life throu^'liout the year 4 Bark beetles likely to be mistaken for the southern pine beetle S Other beetles associated with thi> southern pine beetle !?> Page Natural enemies of the southern pine beetle 15 Preventive measures by forestry metliods 15 Control measures 16 Investigations of outbreaks 18 BEETLE OUTBREAKS AND THEIR IMPORTANCE P VERY FEW YEAES patches of dyin-- and dead pines may be seen throu<:hoiit the southern forests. These group killings can usually be attributed to a bark beetle known as the southern pine beetle.^ Ordinarily it is a rather rare insect, breeding in small num- bers in weakened and dying trees. Periodically, however, favorable conditions occur for development of its brootls, enabling it to in- crease in a very short time from a few individuals to countless hordes. Results of recent investigations of the Bureau of Entomology indi- cate that abnormally dry spells bring about favorable conditions for outbreaks, both by weakening the trees and by creating a more favorable situation in the inner bark for the rapid development of the broods of the beetle. The resumption of normal or heavy precipi- tation effectively checks such development and very nearly eliminates the beetle from the forest. Low winter temperatures also effectively check the increase of the beetle. Other agencies which affect the trees, making it easier for the beetles to overcome their resistance, are fii"e, wind, and lightning. Trees weakened by these agencies, or by mechanical means, constitute a menace to the surrounding forest. Many infestations owe their origin to the attractiveness of a single weakened tree; therefore such a tree should be removed immediately. During periods when the beetles are present in small numbers, abnornuil trees enable the bark beetles to establish themselves and breed up to normal numbers, whereupon they again can become destructive, killing groups of sur- rounding healthy trees. Results of recent studies suggest that trees ^ Dendroctonus frontalis Zimm. ; order Coleoptera, family Scolytidae. 2 FARMERS' BULLETIN 15 86 on burned areas serve as an attraction to the beetles. This is an ad- ditional reason for adequate fire protection. " Blow downs " occur- ring during the summer, as well as the large quantities of timber normally cut at this time, also create conditions which are a menace to the surrounding healthy trees. This freshly cut or damaged timber is frequently attractive to the beetles. There is probably no more serious enemy of pines in the Southern States than this beetle. It attacks and kills healthy, vigorous pines Figure 1. — Map showing distribution of the southern pine beetle. The dots represent known eeuters of infestation of all species occurring within its range, including those of practi- cally all ages. E:^tended observations in the Southern States since 1891 have led forest entomologists to place the present stumpage value of pine killed during this time at no less than $50,000,000. Hopkins - places the value of timber killed by this beetle, during a single epidemic in the South Atlantic and Gulf States in the years 2 Hopkins, A. D. SOUTHERN STATES. THE SOUTHERN PINE BEETLE: A MENACE TO THE PINE TIMBER OF THE U. S. Liept. Agr. Farmers' Bui. 1188, 15 p., illus. 1921. THE SOUTHERN PINE BEETLE 3 1908 to 1911, inclusive, at $2,000,000. In 1922 and 1923 extensive outbreaks of tliis beetle were again reported or ol)served, and a vast quantity of timber was known to have been killed. The latest out- breaks took place in 1925, 1926, and 1927. It is well known that only a comparatively small percentage of the destroyed pine was ever salvaged after these epidemics. There is constant danger that the beetle status may again rise to the danger point. No part of the South is free from this bark beetle. Its outbreaks occur periodically throughout the States of Georgia, Alabama. Mis- sissippi, Louisiana, Texas. Arkansas, Tennessee, Kentuck}', Soutli Carolina. North Carolina, Virginia, West Virginia, Maryland, and Delaware. The beetle is also known to occur in the southernmost Pici;uE — A gi-oup killini;- by the southern pine beetle. Appearance of forest area several years after the trees were killed. Note the new growtli portions of New Jersey, Pennsylvania, Ohio, Indiana, Illinois, Mis.souri, eastern Oklalioma, and northern Florida. Centers of in- festation and distribution are shown in Fiaure 1. EVIDENCE OF BEETLE ATTACK Wherever patches of dying or dead pine are found (figs. 2 and 10) which show no evidence of fire or other destructive injuiy, there need be little doubt that they have been attacked by the southern pine beetle. Tliese trees can be discovered most easily after tlie}^ have been in- fested from 10 days to two weeks, when they display a yellowish- green foliage easily seen from long distances. The color gradually turns to a brownish green, and finally, about the time the beetles emerge, to a reddish brown. Pitch tubes often occur along the FARMERS' BULLETIN 15 86 middle and upper trunk (fi^. 3), but they should not be confused with the larger tubes of the tur})entine beetles ^ which are found near the ground. (Fig. 15.) Reddish sawdustlike borings can often be found sprinkled along the trunk and on tlie ground around the base of the tree. A blue-stain fungus which results in lowering the grade of salvaged lumber is always associated with trees killed bv this beetle. (Fig. 4.) The stain quickly extends to the heart wood. (Fig. 5.) Where any doubt exists as to the species attacking the trees, close examina- tion of the inner bark from the middle of the trunk of the dying trees will posi- tively determine the insect. Here the characteristic wind- ing, S-shaped gal- leries in the inner bark (fig. 6) and on the surface of the wood (fig. 7) can be found, and by re- moving a portion of the outer bark the developing broods can be seen. The burrows of the grubs, or larvae, extend only about half an inch from the parent gal- lery. Here the larvae make oval cells in the outer bark and go into a resting stage — that is, become pupie, before trans- FiGUUE 3. — Pitch tubes made by the southern pine beetle -P--w..,-ri ; n n- inf<-i KQaflao along the middle tiunlj. About one-half natural size lOiming IIILO oeeiies. THE BEETLE: ITS WORK AND ITS LIFE THROUGHOUT THE YEAR Like most insects, the southern pine beetle passes through four dis- tinct stages during its life history. These are the egg, the larva, the pupa, and the adult. The adult (fig. 8, at right) is a small brownish or blackish beetle about one-eighth inch long. It flies throughout the year except during the cooler winter months, when it remains dor- mant within its galleries beneath the bark. It usually attacks the 2 The red turpentine beetle (Dendroctonus valens Lee.) and the black turpentine beetle (D. terebrans Oliv.) THE SOUTHERN PINE BEETLE Figure 4.- -Blue-stained, dead Trees. The blue stain is alway associated witli trees killed by the southern pine beetle FiGUKE 5. — Cro.^h .section of pine tree killed by the southern pine beetle, showing the associated blue stain extending to heartwood, causing a lowering in grade of merchantable timber 6 FARMERS^ BULLETIN 1586 central and upper portions of healthy pine trees (see title-page illus- tration) as well as weakened trees and occasionally ivision of Forest Insects of the Bureau of Entomology, U. S. Department of Agriculture. Washington. D. C, or the Forest Ent( mological Laboratory, Appalachian Experiment Sta- tion, Asheville, N. C. ADDITIONAL COPIES OF THIS PUBLICATION MAY BE PROCrTRED FROM THE SUPERINTENDENT OF DOCUMENTS U. 8. GOVERNMENT PRINTING OFFICE WASHINGTON, D. C. AT 6 CENTS PER COPY V UNITED STATES DEPARTMENT OF AGRICULTURE DEPARTMENT BULLETIN No. 1182 Washington, D. C. T December 12, 1923 THE IMPORTED PINE SAWFLY/ By William Middleton, Scientific Assistant, Forest Insect Investigations. CONTENTS. Faee. Introduction 1 Deseriptions 1 Life history and seasonal history 7 Effect of meteorological conditions 14 Parthenogenesis 15 Page. Parasites 16 Hosts 17 Distribution in the United States 20 Economic importance 20 Control 21 INTRODUCTION. A European insect, the imported pine sawfly,^ has recently been found defoliating young pine trees in nurseries and on estates in cer- tain of the New England and North Atlantic States. This bulletin contains descriptions of the principal stages of the species and some information on its life history, host plants, distri- bution, and importance, together with a brief discussion of its control. The data presented are based on investigations of the sawfly con- ducted at tlie eastern field station of the Forest Insect Investigations, Bureau of Entomology, at East Falls Church, Va. The studies began with the receipt of material in August, 1915, and continued until the spring of 1919, when the last adults emerged in the cages. Inasmuch as the species was an introduced and dangerous one which had not become well established in this country, great care was exercised in the cage work, in order to prevent its escape. A special double-waUed, screen-wire insectary was constructed to which en- trance was had only through a vestibule, and all the experiments were performed on yoimg trees transplanted into this inclosure. DESCRIPTIONS. The following descriptions have been prepared, so that this species can be recognized in its principal stages. Those of the adult are by S. A. Rohwer. ' This bulletin was prepared under the direction of S. A. Rohwer, to whom the author is indebted for many helpful suggestions in conducting the investigations. The descriptions of the adult insects are by Mr. Rohwer. The majority of the material from which these studies were made was obtained from Dr. W- E. Britton, State entomologist of Connecticut. * Diprion simile Hartig, order Hymenoptera; suborder Chalastogastra; superfamily Tenthredinoidea; family Tenthredinidae; subfamily Diprioninae. 63373— 23— Bull. 1182 1 BULLETIIsr 1182, U. S. DEPAKTMENT OF AGRICULTURE. ADULT. This species is the only North .Vinerican representative of the genus Diprion and may be readily distinguished from the other Nearctic species belonging to the subfamily Diprioninae by the large and densely punctured metascutellum. The specmiens which have been examined show very little variation, and all seem to represent the typical form of the species. Female (Fig. 1, a). — Length 7 to 9 millimeters. Clypeus truncate; head with large, rather close punctures; postocellar area convex and more than twice as wide as long; postocellar furrow well defined; antenna distinctly tapering, the joints much broader than long and with very short rami (apical joints practically without rami), third joint distinctly longer than the fourth,; scutum shining, with large, distinct punc- tures; scutellum and met- ascutellum opaque and with the punctures closer; tibial spurs simple; pad- like part of sheath ellip- tical in outline and close to the median line; apical sternite deeply angulately emarginat e medially, lancet with nine rows of regular teeth . Black with yellow markings ; head black except yellow clj^p- eus, supraclypeal area, and scape; thorax yellow with the following parts black: Sternum, mesepi- meron, large spots on pre- scutum and scutum, lat- eral part of scutellar area, and metascutellum; ab- domen yellow with ter- gites 3 to 6 inclusive and median spots on following two black; legs, except the somewhat dusky fem- ora, yellow; \vings hya- line, venation pale brown with stigma somewhat darker and the cost a somewhat paler. il/aZ€(Fig.l, 6).— Length 5 to 7 millimeters. Agree- ing with female in general structure; antenna long, the basal rami slightly less than half as long as half the flagellum; hypandrium dis- tinctly punctured, broadly rounded posteriorly; head and thorax more coarsely punctured than in the female; valves of penis, when seen from the side, broad and the ventral margin armed ^vith small, widely separated teeth. Black; venter of ab- domen and legs beyond trochanters dark rufous; wings hyaline, venation pale brown, costa paler. EGG AND EGG SLIT. The esrgs of the imported pine sawfly are about 1.5 millimeters long, with straight sides and bluntly rounded ends. They are oval in cross section, being 0.5 millimeter on the greater transverse diameter and 0.25 millimeter on the lesser transverse diameter. When first laid the eggs are pale whitish blue, translucent, shining, much like gelatin, and somewhat smaller than the above dimensions. After several days, development becomes marked by swelling and the color appears bluish green. ^Mien about to hatch they are quite swollen, sometimes as long as 1.75 millimeters, and are dark green. (Fig. 2, b.) Fig. 1. — Diprion simile: a, Female; 6, male. THE IMPORTED PIXE SAWFLY. Fig. 2. — Diprion simile: a, Eggs in position in needle; 6, egg, show- ing embryo; c, needle, showing eggs in pockets. The eggs are laid in slits in the needles (Fig. 2, a). Adults emerg- ing early lay in last year's needles, but those emerging when the present year's needles are of sufficient size appear to prefer these. The number of eggs deposited in a single needle varies. In the needles observed, from 2 to 16 eggs were laid, with an average of 8. Where more than one egg is laid the egg pockets adjoin one another, with merely a wall be- tween. The pocket or slit is cut into the convex portion of the needle from an edge at an angle and the tissue composing the walls of the slit is of two textures (Fig. 2, c) . The basal portions of these walls are the rather tough outer coating of the needle and the apical por- tions are delicate membranes, appar- ently made of torn needle pulp, which are pressed together fol- lowing the laying of the egg, seal it in place, and somewhat conceal it. As the egg increases in size, it parts these lips and becomes exposed. When freshly made the cuts are yellowish green and the needle dark green, but as the eggs mature the cuts become somewhat brownish and the needles yellowish. LARVA. The following description ^ was made from a full-grown, sixth-instar larva of Diprion simile which had been preser^^ed in alcohol. (Fig. 3.) Length 20 millimeters; maximum breadth, across the metathorax, 4.5 millimeters. The head is circular in outline viewed from in front and the front plane slightly convex ^•iewed from the side ; frons and epicraniimi with a few fine hairs ; epistoma with 4 hairs; labrum with 4 hairs; eye disks not elevated, eyes large, lenses convex; antennae between and slightly closer to pleurosto- mata than eyes, composed of cone and two disks or partial ring joints; maxillae with cardo, stipes, palpifer and 4-jointed palpi, galea, and lacinia; lacinia not flattened, rather triangular in outline viewed from apex, armed with large hornlike process or seta on the side toward labiurn and with rather large setae fornung an apical transverse row on the side of the lacinia parallel with the interior surface of the trophi; labium \\-ith palpiger and 2-jointed palpi. Thorax with the tergum composed of areas A, B, C, and D; A excepting in the prothorax, B, ' The terminology used in describing the larva is that used by the writer in the descriptions of Neodi- prion lecontei (Fitch) (Jour. Agr. Research, v. 20, no. 10, p. 741-760, 1921), with the changes adopted in "Some suggested homologies between larvse and adults in sawflies" (Proc. Ent. Soc. Wash., v. 28, no. 8, p. 173-192, 1921J. Fig. 3.— Diprion simile: Full-grown larva. 4 BULLETIN 1182, U. S. DEPARTMENT OF AGRICULTURE. and C with a few setfe or spines; A of the prothorax bare and constricted and D bare; alar area wanting or incorporated in the spiracular area of the prothorax, large in the mesothorax and metathorax; in the plenrum, preepipleurite large, w^U defined, and possessing setae or spines; postepipleurite large, well defined, spined in prothorax but bare in mesothorax and metathorax; prehypopleurite large, triangular, of heavy chitin and sparsely, finely haired; posthypopleurite large with a prominent spined lobe; legs with 4 joints and an apical claw, joint 3 with small soft pad on inner side at apex. Abdomen with the tergum of urites 1 to 9 inclusive composed of areas A, B, C\ C^, C^ and D; A, B, and C^ spined, C\ C^ and D bare; urite 10 consists tergally of the epiproct, which is rather thickly spined and without pseudocerci; spiracular area present on urites 1 to 8, wanting on urites 9 and 10; alar area present on urites 1 to 9 (reduced on urite 9), absent or indistinct on urite 10; the pleurum with preepipleu- rite and postepipleurite distinct, rather large and spined on urites 1 to 8, reduced, indistinct, but spined on urite 9, wanting or indistinguishable on urite 10; hypopleu- rite distinct but not divided into prehypopleurite and posthypopleurite, unspined and bearing the iiropods on urites 2 to 8 inclusive, indistinct or wanting on urites 1, 9, and 10; uropods well developed on urites 2 to 8 inclusive, not developed on urites 1 and 9, and developed as postpedes on urite 10. The head is black and shiny, with the eyes yellowish and the membranes about antennae, mandibles, trophi, and between labrum and epistoma whitish. The thorax is yellow, much darkened with velvety black which becomes greenish with growth and age; legs black. The abdomen is yel- low, marked as thorax ; uropods, postpedes, ventral region, and anus undarkened. Most of the body, the tergum and pleurum of the thorax and abdomen is a mottled black and yellow of rather regular pattern. The depressed portions of the body wall are black and the raised portions are yellow, gi^dng much the appearance of a yellow larva dipped in some adhesive black coloring matter and then allowed to wear off the mate- rial darkening its more prominent areas. LARVAL INSTARS. In the study of Diprion simile the experiments on the larvae offered an excellent opportunity to determine the number of larval instars and the size of the larvae during each instar. For conven- ience, this information is arranged in tabular form below. It will be noted that the species has six feeding instars in larvae producing female adults and five feeding instars in larvae producing males. This feature was remarked upon by the writer in treating Cladius isomerus Norton in a recent paper on the subfamily Cladiinae * and is probably common to sawflies, since H. C. Severin ^ records a similar difference in the number of instars between larvas producing male and female adults in his account of Neurotoma inconspicua Norton. The prepupa of Diprion simile is rather well defined and differs from the larva sufficiently in general appearance to be readily recog- nized. * Rohwer, S. A., and Middleton, William. North American sawflies of the subfamily Cladiinae. With notes on habits and descriptions of larvae by William Middleton. In Proc. U. S. Nat. Mus., v. 60, art. 1 (no. 2396), 1922. See p. 19. ' Severin, H. C. The pliim webspinning sawfly. State Ent. S. Dak., Tech. Bui. 1. 1920. See p. 11, 26, tables 2, 3 Severin finds six instars for larvfe becoming males and seven instars for those becoming- females. This larval period, however, covers the entire time spent by the larva; above ground and therefore includes the stage recognized in the present paper as the prepupa. THE IMPORTED PESTE SAWFLY. 5 Table. 1. — Average size of larval instars and prepupa of Diprion simile, in millimeters. Instar or stage. I II Ill IV V (male penultmiate) VI (male prepupa) V (female antepenultimate) VI (female penultimate) VII (female prepupa) Head. Body length. Height. Width. Young. FuU grown. Milli- Milli- Milli- Milli- meters. meters. meters. meters. 0.75 0.50 2.75 6.0 .95 .75 4.00 S.O 1.20 1.00 7.00 12.0 1.60 1.40 8.00 15.0 2.00 1.80 14.00 20.0 2.00 1.80 2 14.00 3 13.0 1.95 1.65 11.00 18.0 2.20 2.00 15.00 25.5 2.20 2.00 2 19.00 3 12.0 Number of larvfE used to obtain averages.* Milli- meters. 1 These larvfe were reared in isolation and measurements were made at frequent intervals. The dimen- sions obtained from them are perhaps few in number but accurate and from an instar or stage positively knov^-n. The averages obtained from these larvse were found to aoplv to larvae in the general rearing cages. 2 Largest. Prepupae do not feed and grow. They contract with development and the spinning of the cocoon. ' Smallest. The different instars of the larvae of Diprion simile are colored as follows : Instar I. — Before feeding: Head whitish, eye spots blackish. Body dull gray. After feeding: Head and legs become blackish. Instar II . — Much the same as ihe first instar. The dorsum darkens somewhat at the approach of the time to shed. Instar III. — Head black. Body green to bluish gray. The day before molting to the fourth instar the larva begins to show dark dorsal, supraalar, and epipleural lines. This change pre\'ious to shedding is doubtless caused by the darker coloration of the approaching instar showing through the skin about to be shed. Instar IV. — Head black. Body considerably darkened, greenish black and yellow, pattern of mottling similar to that of full-grown larva. The larva pales somewhat with age or increased size. Instar V. — Head black. Body velvety black and yellow. The black becomes greenish with age or increased size. Instar VI. — Head black. Body velvety black and yellow. Each instar seems to have two poorly marked phases; first, a rapid growing period, usually covering the greater part of the instar, during which the body increases in length; and, second, a preparatory period preceding molting during which there is a retardation in growth or even occasionally a contraction. The accompanying dia- gram (Fig. 4) shows the records of growth of a male and a female larva in body lengths, instars and days, and illustrates this feature. PREPUPA. The prepupa of the imported pine sawfly does not feed and its development is accompanied by contraction rather than increase in size. The cocoon is spun in this stage and, protected within, the prepupa changes gradually as it develops into the pupa. The following description is from a prepupa preserved in alcohol which had not begun the spinning of its cocoon. Prepupte after spinning do not differ structurally from those which have not spun but are considerably more contracted. A prepupa that is to produce a female adult will measure about 19 millimeters in length before spinning its cocoon, while, after spinning, it will be about 12 milli- meters long. BULLETIN 1182, I'. S. DEPART.MEXT OF AGRICULTURE. The size of the prepupa is discussed under "Larval instars." The prepupa of Diprion simile is similar to the larA-a, in structure, with the armature or spines reduced to indistinctness. The head is gi-ayish white, eye disks and apices of mandibles, only, black. The thorax and abdomen are both pale greenish white, with narrow green, dorsal longitudinal stripes and broader green supraalar to alar longitudinal lines which are broken by yellowish spots on B, C ', C^, the pale spiracular area, and the yellowish alar area. Pleurum pale but for a pair of greenish pleural spots, ^'enter, uropods, postpedes, anus, and epiproct pale, the latter faintly graAash. COCOON. The cocoons (Fig. 5) of Diprion simile are cylindrical, with hemispherical ends. They are single-walled, of fine texture, rather glossy, fairly stiff, but tliin. Cocoons from wliich males emerge are somewhat smaller than those from wMch females issue, 7 by 3.5 millimeters being the size of the former, while the latter are 9.3 by 4 mili- meters. The cocoons are usually dark brown; sometimes they are pale tan when made but become dark brown within a week or 10 days, and in one instance a whitish cocoon was spun which failed to become colored. A^^V Ai^yAy ^U^^" Ci CM '^l- '-0 <^, S) ^ > ^ !? ?i ^ ^ I ^ <'-•?. -^. ^ Oj ^J (\i c\j c\i ^<^ ^ '^ I Fig. 4. — Diprion simile: Larval growth charts. Stage of larva indicated by large figures. Female has six stages, male five. Growth records are shown for a single female and a single male larva. In captivity the cocoons were often spun on the needles, and while this may be the rule in nature the "writer is inclined to believe that many of the prepupte of this species, like those of Neodiprion lecontei, will make their cocoons in the ground for the sake of the protection thus afforded in winter. This view is supported by a European observation ^ which records the summer brood cocooning on the branches of the tree while the winter brood makes its cocoons beneath the tree. The cocoon is spun of a ''silken" thread from the vicinity of the mouth.'' The end of the cocoon inclosing the caudal extremities of the prepupa is made first, then the anterior end is inclosed by a sidewise motion of the head. After the entire cocoon is formed the prepupa works over the inside, plastering a sticky substance to it. This coating makes the glossv inner surface. « Britton, W. E. A destructive pine sawfly introduced from Europe. In Jour. Econ. Ent., v. S, no. 3, p. 379-3S2. 1915. .S'ffp.3M. ' This thread doubtless comes from the apex of the labium, where the writer has observed a similar sub- stance protruding in some prepupse of Cimbez americana l.each in his possession. THE IMPORTED PINE SAWFLY. I LIFE HISTORY AND SEASONAL HISTORY. The experiments to obtain data on the hfe history and seasonal history- of Diprion simile were distinct from those pertaining to the choice of host phmt and also from those pertaining to the abilitv of the insect to reproduce parthenogenetically. Pinus sylvestris was chosen as a host for this work because it seemed to be favored by the sawfly and because it had been shown to be a successful host in this locality by previous tests. In no instance was copulation- observed, but opportunity for fertilization was provided by keeping constantly with each female at least two males in excellent condi-^ tion. These experiments were made with small cylinder cages of screen wire on a steel frame. 14 inches in diameter by 24 inches high, the top of which was removable to permit easy access to the interior for observation or handling the material. These cages were placed over young trees of Pinus sylvestris, and adults of Diprion simile were then libe- rated within. There were also certain spe- cial life-history and seasonal-history stud- ies, particularly some in which observations were made on larva? of this sawfly reared in isolation to deter- mine the number and duration of the instars and the influence of the sex of the individual upon this phase of development. The data presented in the following account of Diprion simile show some singular likenesses and contrasts with the life of the related Neodiprion lecontei.^ It would be well to emphasize that the imported pine sawfly has the same apparent division of the emergence period into Broods A and B. It dift'ers somewhat from Leconte's sawfly in the course of its issuance, a fact which may be explained either as inherent in the species or as caused by change of environ- ment. The climate and other natural factors in the United States may be so difl^erent from those to which it is accustomed that it is unstabilized here. Should this prove true, the situation with regard to Diprion simile may become very difi'erent within a few years, and the insect may even become a more serious problem than it now promises to be. " The imported pine sawfly has important life-history and seasonal-histor}'^ advantages, and if it can become a recognized depredator while unstabilized by the conditions of this new environment, the destructive possibilities of the species when it is properh' adjusted will be necessarily greater. In that case it may possibl}' present a new life history and seasonal history. ADULT EMERGENCE. The emergence of adults from the cocoons of a single colony of the larvffi of Diprion simile occurs over a considerable period, approxi- mating a vear. This emergence is not continuous, but divides itself Fig. j. — Diprion simile: Cocoons, o. Occupied by female, unopened; 6, occupied by male, unopened: c, after emergence of female; d, male cocoon, showing emergence hole of a chalcid parasite; e, fe- male cocoon, showing emergence hole of a dipterous parasite. 8 iDddleton, William. Leconte's sawfly, an enemy of voung pines. In Jour. Agr. Research, v. 20, no. 10, p. 741-760. 1921. "S BULLETIN 1182, U. S. DEPARTMENT OF AGRICULTURE. into a period early in the year and a period late in the year. The adults are separated into Brood A, those issuing in the first emer- gence period following cocooning, and Brood B, those issuing in the second emergence period following cocooning. The early emergence period occurs from April to June and is not distinctly separated from the later emergence period, which occurs during July and August. The rearing cages, however, show a marked decrease in the number of adults coming from cocoons during June. The following summary of records of the issuance of adults shows the duration of this period and its tendency to divide into two parts, the months of maximum emergence being April, May, and July. Larvae and pupae collected in August, 1915; 1 adult emerged in August, 1915. 77 adults emerged in May, 1916. 5 adults emerged in June, 1916. 1 adult emerged in July, 1916. Cocoons collected in April, 1917: 16 adults emerged in April, 1917. 95 adults emerged in May, 1917. 2 adults emerged late in June, 1917. 2 adults emerged in July, 1917. 1 adult emerged in April, 1918. Larvae cocooning in June of various years: 2 adults emerged in June of the same year in which they cocooned . 24 adults emerged in July of the same year in which they cocooned. 1 adult emerged in August of the same year in which it cocooned. 7 adults emerged in April of the year following that in which they cocooned. 8 adults emerged in May of the year following that in which they cocooned. LONGEVITY OF ADULTS. The average length of life for adults of Diprion simile was 6.6 days, with a range from 3 to 11 days. The life of the female was slightly longer than that of the male, the former averaging 7.5 days, with a range from 5.5 to 11 days, while the latter averaged 5.8 days, with a range from 3 to 9 days. The life of female adults known to have laid eggs was somewhat longer than the life of those not known to have laid eggs. Females laying eggs averaged 7.75 days, those not known either to have laid eggs or not to have laid eggs averaged 7.66 days, while those known not to have laid eggs averaged 7 days. The two shortest-lived males were the progeny of parthenogenetic females. Only two of these were available for this study, and these lived, one 3 and the other 4 days. PROPORTION OF SEXES. The males seem somewhat to exceed the females in number, and from a series of 227 adults issuing from cocoons in certain of the cages, 134, or 59 per cent, were males, while 93. or approximately 41 per cent, were females. MATING. Mating was not observed. At different times three males were caged in glass vials with a single unfertilized female without their paying her the slightest attention. This, however, was probably due to the close confinement of the sawflies under observation, which tended to distract them and prevent or discourage natural behavior. The fact that from the life-history and seasonal-history THE IMPORTED PINE SAWFLY, experiments both sexes were obtained in the progeny, wliile, as will be stated farther on, in parthenogenetic experiments only male adult^ were obtained, indicates that mating is a regular occurrence. OVIPOSITION. The eggs are laid in the needles of the pine and the adults emerging from their cocoons early in the year oviposit in the old or last year's needles, while the adults emerging later in the year lay their eggs in the needles of the current j^ear. The following note, made in obser- vations on the habits and activities of the adults in the life-history and seasonal-history cages, shows the increase in attractiveness of the current year's needles. All the females, except the one emerging at the latest date, i. e., June 23, 1916, laid their eggs in the old or grown needles, but this female, possibly because of the advance of the younger needles, delayed her oviposition several days and then apparently first attempted egg laying in these new leaves. After two slits or thrusts, possibly having succeeded in laying an egg in one of these, she began on the old needles and finished her work on them. This note seems to indicate a preference for the young needles which were still too small for this female to oviposit in them. The following account, taken from cage notes made during these experiments, gives an accurate description of the method of ovipo- sition: The female begins laying eggs near the base of the needle and works toward the tip, making a new incision for each egg. In oviposition the mandibles usually close upon the needle; the antennse extend forward and are usually quiet and the wings are folded, at rest on the back. The ovipositor (Fig. 6, b, c) is exserted from between the right and left halves of the sheath, forming an angle of about 60° with the needle. It is worked into the needle and straightened until as it disappears it forms a right angle with the needle, saw edge forward (Fig. 6, a). The posterior margin of the seventh sternite is membranous and is produced medianly to form a sort of trough (tr) for conveying the eggs into the slit prepared for them. The sides of the trough are supported by a pair of diverging chitinous pieces or more ri»id areas. This trough during o\'iposition is immediately in front of the slit that is being cut and serves as a support to the abdomen, maintaining a constant distance between body and needle and contributing to a rigidity and firmness of the base of the working parts in their relation to the needle. Posterior to the trough and basad of the sheath proper there is a pair of rather small rectangular plates or trowels (t) (Fig. 6, d), one plate at each side, attached to the base of the basal portion of the sheath (sh^) and appearing similarly attached to the base of the lance (le). These plates were observed for the first time in this insect and are not found in Neodiprion lecontei, which belongs to the same subfamily, nor has the writer been able to discover similar developments in sa\vflies outside of the Diprioninae. The function of these plates or trowels is apparently to support and mold the torn needle fiber into walls and'cover for the egg pocket. The sheath {sh'- and sh'^) is posterior to these plates (t) and its right and left halves cover respectively the right and left sides of the needle at the point of incision. During the sawing there are alternate contractions and expan- sions of the pleurum of the ninth urite which cause the sheath to flex or bend at the juncture of the basal (sh^) and apical (sK^) portions, and a side-to-side oblique move- ment of the trough (tr). The saw is worked or dragged until the trough (tr) reaches the mesothoracic legs. The puncture is then complete and the abdomen is slightly ele- vated. The trough (tr) and the trowels (t) are now pushed back together, smoothing off the torn fiber at the mouth of the pocket and bringing together the walls of the cavity at its opening. The saw is withdrawn at the same time. It is not visible except through the needle tissue, being hidden by the trowel (i), and its withdrawal is accomplished or accompanied by a backward, upward folding movement. The entire egg-laying process consumes about two minutes. 53373— 23— Bull. 1182 2 10 BULLETIN 1182, U. S. DEPARTMENT OF AGEICULTURE. Oviposition occurs over several days, the female going from needle to needle. Table 2 indicates the number of eggs laid and gives an idea of the number of needles upon a tree that are attacked. ■URS Fig. &.—Diprion simile: Ovipositor, a, Apex of abdomen of female adult in position over nearly com- pleted egg slit (enlarged); 6, three-quarters ventral view of apex of abdomen of female adult (enlarged); c, ventral view of portion of egg-laying apparatus of female adult (much enlarged); d, side view of trowel, from ovipositor of adult female (greatly enlarged). Table 2. — Oviposition records of Diprion simile. No. Number of needles oviposited in and number of eggs in each. Total number of eggs. Host plant. « 1 2 9 0 9 3 4 5 6 7 8 9 10 1 3 9 5 26 9 53 27 68 SI Pinus austriaca. P. laricio. P. sylvestris. Do! Do. >> 3 11 1 16 12 2 12 2 5 10 11 7 3 S 6 6 5 6 9 4 5... 6... 12 12 11 4 8 13 2 14 5 7 8 2 Of these experiments the first and second were failures owing to the host plant chosen, and the eggs in the third and fourth were laid by virgin females, and therefore will be treated farther on, in consider- ing the experiments on parthenogenetic reproduction in this species. THE IMPORTED PIXE SAWFLY. 11 Table 3 shows the length of time elapsing between the emergence of the adult and oviposition. Table 3. — Preoviposition period of adults of Diprion simile. No. Date adult emerged. Date oviposi- tion began. Time in days from emer- gence to oviposi- tion. Host plant. Remarks. 1... Mays... Mav9..- MayU.. Mayll.. 3... I May 12.-! May 16.. 4...! Mays...! May 10.. 5...; May 9... May 11.. 6..-! June20.. June23.. Pinus sylvestris. do Pinus austriaca.. Pinus sylvestris. do do Host plant unfavorable. Unfertilized female. Do. New needles attractive. From the consideration of all the available data the writer is of the opinion that a fertilized female will begin laying eggs soon after fertilization, provided material suitable for oviposition can be found. Such was the case with the first and second females in Table^ 3. Unfertilized females will begin laying after a two-day period during which they await mating, provided that suitable material is con- venient, as shown by the fourth and fifth females, which were used in experiments on parthenogenetic reproduction. A period of longer than two days presumably indicates an unfavorable host, unfavor- able condition of host, or other disturbing factor. In the instance of female No. 3, the four-day delay is believed to indicate that Pinus austriaca is an unfavorable host, a conclusion borne out by other observations discussed under ''Hosts." In the instance of female No. 6, the three-day delay is believed to have been caused by the advanced condition of the young needles, which, though not of sufficient size for successful oviposition, were yet large enough to attract her and thus lengthen the time between emergence and oviposition. FERTIUTY AND INCUBATION. In only one of the experiments was an accurate record of the eggs from laying to hatching kept, and here it was found that 48 eggs out of 69, or 69.5 per cent, hatched. The period of time elapsing between oviposition and hatching is called the incubation period. Table 4 records the results of investigations to determine the length of this period. Table 4. — Incubation period of Diprion simile. Date laid. May 9 to 15... May 10 May 11 to 15.. Do May 16 June 23 to 24. Date hatched. May 22 to 26. May 22 May 25 to 29. do May 29 July 1 to 2.... Length of period.! Host. Days. 11-13 12 14 14 13 Pinus sylvestris. do do do Pinus austriaca . Pinus sylvestris. Remarks. Unfertilized f emalo . Do. » In counting the number of days in the incubation period, it was assumed that the first eggs laid were the first to hatch and that the latest laid were the latest hatched. 12 BULLETIN 1182, U. S. DEPARTMENT OF AGRICULTURE. For eggs laid about the middle of May (May 9 to 19), from 11 to 14 days were required for development to the point of hatching, aver- aging 12.8 days. For eggs laid in late June, 8 days sufficed for development. Fertilized and unfertilized eggs, apparently, did not differ in the duration of the incubation period. LARVAL DEVELOPMENT, The larviB of the imported pine sawfly shed their skins as they- develop. The periods between moltings of the larva are called in- stars. The number of instars, the difference in the number between larvne producing female adults and those producing males, and the size and appearance of the larvae in each of the various instars have been treated under "Larval instars." Table 5 shows for a number of larva? the time spent in each instar, the average length of the instar, and the total length of the larval or feeding period. This table is arranged to show sex and date of hatching of each individual or group of individuals, because the sex makes a difference in the number of instars, and the rate of develop- ment of the larv« appears to be accelerated as the season advances. Table 5. — Number and length of larval instars of Diprion simile, showing individual's date of hatching and sex. Sex. Length of instar. Date egg hatched. Instar I. Instar II. Instar III. Instar IV. Instar V. Instar VI. Total. May 81.. Male.... ...do . Days. 6 6 7 6 6 7 6 4 Days. 5 5 5 4 4 4 5 7 Days. 3 4 4 4 4 4 5 7 Days. 6 5 4 4 4 6 4 5 Days. 12 11 9 11 10 2 6 3 Days. Days. 32 Do.i 31 May 91 ...do 29 May 12'.. do 29 jjDo.i .do . 28 May 222 ...do 23 May 252.. do 26 D0.2 26 do Extremes 4 to 7 6 4 to 7 4i 3 to 7 41 4 to 6 4J 2 to 12 8 23 to 32 Average early.. ...do . do 28 July 1 4 5 2 3 2 16 ...do Average mid- 4 5 2 3 2 16 Female.. ...do.... May 9 9 6 6 4 4 4 5 4 4 3 2 2 6 5 4 10 9 9 37 May 12 30 Do ...do 29 ...do 6 to 9 7 4 to 4 4 4 to 5 4J 2 to 3 2J 4 to 6 5 9 to 10 9J 29 to 37 Average early.. ...do 32 > Isolated for stages. LARVAL HABITS. 1 Cage work. IF' The larvse from the time of hatching to the latter part of the second instar or the beginning of the third feed only on the exterior of the needles, expecially from the angles or sides. They then begin to consume the entire needle. At about the fourth or fifth instar they attack the young shoots, feeding on them basally to an extent sufficient frequently to cause the shoots to die and fall. This habit of feeding on the shoots is not essential to the development of the THE IMPORTED PINE SAWFLY. 13 larvae, since caged individuals supplied with needles complete their growth successfully and become adults; nor does it, among those larvag practicing it, supplant needle eating. PREPUPAL AND PUPAL PERIOD. When the larvfe have finished feeding they evacuate their ali- mentary tracts and shed their skins, becoming prepupae. They then crawl about until each finds a suitable place and spins its cocoon. The length of time spent in the prepupa stage varies considerably. When adults emerge the same year this stage may be as brief as 10 days, when they emerge the following year it may be as long as 341 days. Table 6 records the results of some experiments to determine the length of the prepupal period and the time spent within the cocoon. The prepupal period as recorded in this table is not separated from the pupal period. It is difficult to determine the exact duration of the pupal period. It seems to be brief and the pupa is seldom obtained by cutting open cocoons, the insects being nearly always found in the prepupal or in the unemerged or immature adult stage. Table 6. — Dates of becoming prepupa, of cocooning, and of emergence. ADULTS EMERGING THE SAME YEAR IN WHICH THEY COCOON. Indi- vid- ual No. Host plant. Date individual became prepupa. Date cocooned. Days between time insect became a prepupa and co- cooned. Date adult emerged. Days in cocoon . Days between time insect became prepupa and emerged as adult. 1 2 Pinus cembra June 29,1917 July 2, 1917 June 29,1917 June 18,1917 June 29,1917 .do 3 July 9,1917 July 7, 1917 June 27,1917 July 9, 1917 do 7 8 9 10 10 13 25 10 3 4 5 6 June 22,1917 July 5,1917 Aug. 1,1916 7 do ; July 3,1916 July 7, 1916 4 29 3.5 11.7 19.5 ADULTS EMERGING THE FOLLOWING YEAR. P. flexilis P. taeda P. monticola.. P. divaricata. P. virginiana. P. sylvestris.. do Average. July 11,1917 Jime 15,1918 July 9, 1917 July 12,1917 June 29,1917 do do June 22,1917 June 17,1918 2 1.5 Apr. 15,1918 May 2, 1918 Apr. 24,1918 May 5, 1918 May 6, 1918 May 3, 1918 May 22,1919 280 294 299 310 311 315 339' 295 341 318 SUMMARY OF LIFE HISTORY AND SEASONAL HISTORY. Variations in the length of the several stages of Diprion simile, due to known factors such as season, sex, etc., or to unknown factors such as what determines the prepupa to emerge the same or the next year, cause variations in the total length of the insect's life cycle. Table 7 indicates the various lengths of life and periods to be expected. 14 BULLETIN 1182, U. S. DEPARTMENT OF AGRICULTURE. Table 7. — Life chart {average) of Diprion simile. Progeny of adults issuing in the spring. Progeny of adults issuing in summer. Period. Adults emerging same year as co- cooning. Adults emerging the next year after cocoomng. Adults emerging same year as co- cooning. Adults emerging next year after cocooning. Male. Female. Male. Female. Male. Female. 1 Male. Female. Incubation period — Days. 12.8 Days. 12.8 Days. 12.8 Days. 12.8 Days. 8 Days. 8 Days. 8 Days. 8 Larval period: First stage 6 41 8 7 4 44 f 9J 6 .41 7 1 5 9i 4 5 2 3 2 . 4 5 2 3 2 Second stage Third stage Fourth stage Fifth stage Sixth stage Total 28 10 5.8 32 10 7.5 28 341 5.8 32 341 7.5 16 1 1 18 29 1 29 5.8 : 7.5 16 295 5.8 1 18 Prepupa (including pupal period) 295 7.& Total 56.6 62.3 387.6 393.3 58.8 62.5 324.8 328.5- 1 Obtained by rule of proportion, as no isolation for length of larval stages gave female adults. The accompanying chart (Fig. 7) gives a general view of the activities of this species covering a period of about four years, especially the relations existing between stages, broods, generations, and colony periods, and shows the possible opportunities of the species to inbreed and crossbreed among the various colonies, broods, and generations.. EFFECT OF METEOROLOGICAL CONDITIONS. The notes on the effects of meteorological conditions on this species are incomplete and do not lead to any definite conclusions with regard to the part climate will play in its establishment or in the restriction of its range in America. The small number of adults obtained in the rearing experiments undertaken under the life- history, seasonal-history, and host-plant work gives the impression that the climate of the section of tne country where this work was undertaken. East Falls Church, Va., near Washington, D. C, is rather unfavorable for Diprion simile, while the apparent establish- ment of the species in New England, New York, and New Jersey points to the suitability of a somewhat cooler climate. In the cage work, where the rapidity of development was noted^ it was observed to be accelerated by increased temperature. Table 8 records the duration of stages and instars in days for two colonies of Diprion simile between which there was a difference of 46 days in the date of egg laying, and shows the average temperature during each of the stages or instars. THE IMPORTED PINE SAWFLY. 15 Table 8. — Effect of time of year and temperature on rate of development of the egg and larval instars of Diprion simile. Earlier colony. Later colony. Stage. Date stage or instar began. Time in stage or instar. Average tempera- ture in stage or instar. Date stage or instar began. Time in stage or instar. Average tempera- ture in stage or instar. Egg 1916 May 9 22 29 June 2 6 12 17 29 Days. 13 7 4 4 6 5 12 ° F. 61.61 68.78 64.50 66.25 64.33 67.90 70.46 1916 June 24 July 1 5 10 12 15 17 24 Days. 4 5 2 3 ? 0 jr. 72.85 Larval instar: I 71.25 II 72.70 Ill 77.75 IV 79.00 V 75.25 VI 76.28 Total 51 66.19 30 74.51 Some scattered observations record the larvsB feeding close to the trunk on a cool and rainy day (temperature 60° F., humidity 87 per cent) , feeding vigorously and spread out on a warmer and less humid day (temperature 69° F., and humidity 68 per cent), and clustered on needles close to the bole on a still warmer and drier day (tempera- ture 85° F., humidity 40 per cent). These observations would seem to indicate a rather low optimum temperature, somewhere between 69° and 85° F., with a rather delicate responsiveness to any consider- able variation in temperature, and the fact that the larvae were observed to be rather slow in developing during a damp period and inactive during a cool, rainy spell (temperature 56° to 71° F. and humidity 85 per cent) tends to show a similar sensitiveness to humid- ity. The observations, however, are too few and were made in too restricted an area to be of much value. PARTHENOGENESIS. Diprion simile can reproduce parthenogenetically; that is, eggs laid by virgin females are fertile and hatch, producing larvae which grow, become prepupae, spin cocoons, and finally emerge as adults. All the adults thus far obtained from eggs of unfertilized females, however, are males, a result believed usual for parthenogenetic reproduction in sawflies. Females that have not mated appear to wait two days before com- mencing oviposition, as shown in Table 3, but after this period passes they begin to lay unfertilized eggs. Two of the experiments per- formed to obtain these unfertilized eggs were successful, one female laying 53 eggs, the other 27. A comparison of the number of eggs laid parthenogenetically with the number laid by a normal fertilized female indicates that the virgin female lays only half as many eggs as the fertilized female. In the two parthenogenetic experiments in which eggs were deposited about 72^ per cent of the eggs hatched, which is approxunately the same as the percentage of hatching obtained from eggs of fertilized females. The mortality among the 16 BULLETIN 1182, U, S. DEPARTMENT OF AGRICULTURE. ^1 ! IIP T _ pi i\.-J- ^! 1 I--I- t- ^r ---- ^' I il (Vn ^ "*" ' 1 ^Iii5 J-ll t I't*) i^*) ^x^ cl§§ S§§ t'^'^ ife ^^t ^11 §11 ill §11 ■c25 .1-32 Is •S-cg 1:8 S "a-B o o t, o o y, a I'ii P*ttl o rao3 P Of-*© to P< _ , a > p "^ /fl "-I ° S t^ • P< 5 ffl « 5" •3_, -a 2 ci °-^ §2 c'S m > u 2iil „ o O ^ fe c S C M g C3 &■§ "-g •-Hi "■^ c f; *-• -"^ ^ .~.>a „^ i.|2<; larvae, however, was higher in the progeny of virgin females, and few survived to become adults. It may be that larvse wanting male parents are lacking in vitality and when developing to the adult produce an insect with less viability. This is indicated by the death of a great percentage of the larvae under ap- parently favorable conditions and the shorter life of adults from eggs laid by unfertilized females. PARASITES. Only two species of natural ene- mies were obtained from the experi- ments performed at the eastern field station, East Falls Church, Va. These were Dihrachys nigrocyaneus Norton and a species of Eur^^toma. Britton and Zappe" record the following: Hymenoptera: Dibrachys nigrocyan- eus Norton, Monodontomerus dentipes Boheman, Dibrachoides verditer Nor- ton, Delomeristan. sp.,Cerambycohius sp, (probably new), Eurytoma sp., Hemiteles utilis Norton. Diptera: Exorista petiolata Coquillett. All parasites specifically identified are native species, with the excep- tion of Monodontomerus dentipes Boh., which is a European species already recorded from the United States. Dibrachys nigrocyaneus was rather abundant, much more so than any of the other species, and Britton and Zappe state that only the first three species recorded in their list given above were reared in sufficient num- bers to indicate that they are at all effective in holding the pest in check. Table 9, from Britton and Zappe, gives the general results of an exam- ination of cocoons collected during the winter of 1916-17. A short experiment on the length of life of Dibrachys nigrocyaneus Nor- ton was performed. From 65 adults caged without food all the males died within three days and all females » Britton, W. E., and Zappe, M. P. The imported pine sawfly. In Conn. Agr. Exp. Sta. Bui. 203, p. 273-290, 1917. See p. 283. THE IMPORTED PINE SAWFLY. 17 within eight days ; and from 40 adults supplied with cotton soaked in sugar water all the males died within three days, but all the females, except 1, were living on the thirteenth day, and all were not dead until the seventeenth. Table 9. — Cocoons of Diprion simile collected during the winter of 1916-17 and examined for ■parasites. Condition. Number. Per cent. Adult sawflies had emerged 1,321 1,210 191 518 41 Parasites had emerged 37 Tom open and eaten 6 Dead 16 Total 3,240 100 Several experiments were made with D. nigrocyaneus Norton, with the object of observing oviposition and studying the relation of the parasite to this host. All resulted in failure, however, for no parasi- tism was obtained, although the chalcids endeavored to oviposit, usually more than once, in the cocoons supplied. Possibly D. nigrocyaneus does not attack Diprion simile in the cocoon stage. The presence and activity of these parasites must not lead to the conclusion that they will bring about an effective natural control of D. simile. If the permanent establishment of this pest is to be pre- vented, or if its multiplication and work are to be checked, artificial control measures, such as those recommended, must be applied. HOSTS. If the imported pine sawfly is able to feed on a number of species of pine this will be an important factor in the establishment of the species in this countr}'', and it is extremely desirable to know if it can and will use our native pines successfully. Restricted to intro- duced ornamental species of pines, Diprion simile would at worst only become a nursery and estate problem, but if it will attack our Ameri- can pines it may become a serious forest problem. At present the sawfly seems to be confined to young pines of imported species and has only been recorded from nurseries and estates. To determine the range of host plants which this insect can success- fully utilize, two series of host-tree experiments were conducted. One was to determine the ability of Diprion simile to use a given host suc- cessfully from oviposition to the production of adults. The other was to determine the preferred host plants of the sawfly, if there are any. In the first series of experiments a number of adult males and females of D. simile were confined upon a particular species of young pine to observe its suitability. In the experiments on choice of host species a quantity of small native and introduced pines were transplanted into the large screen-wire insectary previously mentioned and a number of males and females liberated within the inclosure. Table 10 gives the results of the experiment to determine the im- ported pine sawfly's choice of host plants. Fifty-four male adults and fifty-nine female adults of D. simile were liberated in the insectary, 18 BULLETIN 1182, U. S. DEPARTMENT OF AGRICULTURE. into which the follo\^dng species of young pines had been trans- planted. Number of trees Species. placed in insectary. Pinus austriaca 2 Pinus cembra 2 Pimis divaricata 2 Pinus llexilis 3 Pinus laricio 4 Pinus monticola 3 Number of trees Species. placed in insectary. Pinus ponderosa 5 Pinus resinosa 3 Pinus stroljus 5 Pinus syh estris 1'^ Pinus taeda 1 Pinus virginiana 3 Twelve species and a total of forty-eight trees. In Table 10 the host trees are arranged according to the number of trees of each species that were chosen by the females for oviposi- tion and the suitability of these pines as hosts is indicated by the number of individuals of the sa\^^y that were able to develop through the variaus stages from egg to adult. Frequency of selection for oviposition has been considered a some- what better guide to the appeal of the various pines to the sawfly than the numbers of the different stages of the insect obtained. This is especially true where the number of adults obtained exceeds a third of^the total number of larvje, since the larvae after hatching were cage-reared, and, although protected from parasites, doubtless experienced a number of difficulties due to handling and to their artificial surroundings. The species of pines believed most favorable for D. simile are therefore placed at the beginning of the table. Table 10. — Experiment to determine the host-plant preference exhibited by Diprion simile. Species and serial number of host tree. Number of trees of species chosen. Eggs. Larvae. Cocoons. Adults. Pinus sylvestris, trees 1, 20, and 29 strobus, trees 5 and 6 cembra, tree 2 virginiana, tree 14 divaricata, tree 1 monticola, tree 2 flexilis, tree 2 taeda, tree 9 resinosa, trees 16 and 18 austriaca, tree 2 1 x=niunber not counted. 2 27 larvffi killed— rain. '?= trees examined and no eggs found. Therefore, while it is possible that eggs may have been over- looked, it is also possible that a larv-a dropping or knocked from another tree may have reached these; consequently these species can not be given fuU credit for choice. Table 11 gives a summary of experiments in which adults of Diprion simile were confined in cages on single young trees of certain species of pine. It shows in some degree the greater success attend- ing the use of Pinus sylvestris as a host for the sawfly. ! THE IMPORTED Pi:>^E SAWFLY. 19 Table 11. — Experiments shoiving the results accompanying the forced use of certain species of pine as hosts by Diprion simile. Species and serial number of host tree. Parent females. Eggs. Larvse. Cocoons. Adults. Pinus svlvestris: Tree 1 1 1 1 1 1 1 1 1 1 1 2 3 1 1 1 2 1 3 2 i Tree 2 9 1N9 79 53 27 68 3 21 48 43 IS 2 Trees 4 and 5 Trees 6 and 3 9 Trees 1.5 and 16 0 2 Trees 18 and 19 1 Tree 20 Tree 21 9 3 2 1 Tree 29 Tree 30 6 5 4 Pinus austriaca: Tree 1 Tree 2 26 5 Pinus divaricata, tree 36 Pinus flexilis, tree 1 i 9 13 29 Pinus strobus: Tree 16 2 6 Tree 17 > N=needles in which eggs have been deposited but the number of eggs not counted. * x= number not counted. Britton and Zappe/" in their paper on this species, give the follow- ing list, in which the pines are arranged " according to the preference shown by the sawflies in nature and to the largest number of sawfiies reaching maturity" in their host-plant experiments: Pinus excelsa Wall. Bhotan pine Pinus cembra Linn. Stone pine Pinus flexilis James. Limber pine ^Five-needled pines. Pinus strobus Linn. \^'Tiite pine Pinus koraiensis Sieb. & Zucc. Korean pine Pinus montana Du Roi. Mugho pine Pinus densiflora Sieb. & Zucc. Japanese red pine. Pinu^ resinosa Ait. Red pine Pinus sylvestris Linn. Scotch pine Pinus ponderosa Dougl. Bull pine Pinus laricio Poir. var. austriaca Endl. Austrian pine >T\vo-needled pines. Pinus rigida Mill. Pitch pine Three-needled pine. This list shows that Diprion simile has a decided preference for the five-needled and the softer two-needled pines. A comparison of this list with the writer's experiments shows an agreement as to the preference for the five-needled pines and the apparent lack of suitability and attraction possessed by P. laricio, P. austriaca, and P. ponderosa, but a disagreement regarding P. sylvestris, which was a favored tree and capable of carrying the species from egg to adult in the writer's cages, while, along with P. ponderosa. and P. laricio variety austriaca, it was almost immune to infestation in the experiments of Britton and Zappe. From these data it seems reasonable to suppose that Diprion simile is capable of utilizing several of our American pines as hosts and therefore may succeed in establishing itself in the forests of the United i» Britton, W. E., and Zappe, M. P. Op. cit., p. 27S. 20 BULLETIISr 1182, U. S. DEPARTMENT OF AGRICULTURE. States. Furthermore, the species of pines represented above are from sufficiently different sections of the country to make available a possible host in most of our pine-growing regions and in such a variety of climates that some of them must be favorable for the insect's development. DISTRIBUTION IN THE UNITED STATES. Diprion simile is known to occur in nurseries in Connecti- cut, New York, Penn- sylvania, and New Jersey. Specimens have been received from Massachusetts, and the species is re- corded from Indi- ana.^^ The history of the sawfly in the United States suggests that it was introduced with imported nur- sery stock, a view which is supported by the fact that in Connecticut, New Jersey, and Massa- chusetts it has been intercepted at quarantine inspection ports. The following list gives the localities from which the species is recorded (see also Fig. 8) : Connecticut: Derby, Greenwich, Hartford, New Canaan, and New Haven.'' Indiana. Massachusetts. New Jersey: Elizabeth, Rutherford, and South Orange. ** New York: Flushing, L. I. Pennsylvania: Chestnut Hill '^ and Penbrook." ECONOMIC IMPORTANCE. The imported pine sawfly is to be regarded as an extremely danger- ous visitor in the United States, because in Europe, where it is asso- ciated with Diprion pini L., the two are responsible for an immense amount of damage. D. pini has usually been considered the chief cause of this injury, but the two species are so closely allied ^* and so frequently confused that the presence of D. simile in this country must be regarded with apprehension. In Europe D. pini ^^ is accred- ited with serious damage to pine in southwestern Russia, in 1914 de- foliating rnany acres of pine in the districts of Achtyr and Izium; in Germany, in Prussia, and particularly in Brandenburg and Silesia, in " Britton, W. E., and Zappe, M. P. Op. cit., p. 275. " From a letter from Harry B. Weiss, dated Aug. 12, 1916. " Localities for specimens determined by S. A. Rohwer. M Diprion simile Hartig has been considered a synonjon of D. pini L. » Bntton, W. E., and Zappe, M. P. Op. cit., p. 276." FiG.S.— ZJj'prjon simile: Distribution in the United States. Around black spot indicates a report from a definite locality; a square spot indicates occurrence in the State, but without definite locality. THE IMPORTED PINE SAWTLY. 21 1914; in France, in 1906; in Sweden; in Norway, in 1914, when the larvas nearly defoliated 10-year old pines on one plantation; and in England, where they are said to injure Scotch fir as well as pine. In many of these infestations D. simile doubtless took a prominent part and in some instances may have been the chief depredator. Should D. simile become permanently established in this country, it will be capable of great destruction. At present it is probably confined to nurseries and estates, where it is doing sufficient damage to attract considerable attention, and nurserymen and gardeners are endeavoring to exterminate it. CONTROL. In the United States the seeming preference of Diprion simile for young trees makes this saw^y primarily a nursery pest and a nur- sery problem rather than a forest problem. This confinement to trees in nurseries and on estates is of considerable advantage in an attempt to eradicate or control the species, since in such situations the best opportunities for combating it are found. The infestation is more easily observed early in its course, and methods of control can be employed which, despite their effectiveness, could hardly be recommended to check a forest invasion, owing to the inaccessibility and vastness of the area. Because infestations of the sawfly are at present limited to young trees in nurseries and under similar condi- tions, it is doubly important to combat it now, first, to check its rav- ages, and, second, in the hope of exterminating it or at least pre- venting it from ever becoming established in our forests. In the effort to control the species its life-history and seasonal- history advantages, already referred to, should be taken into con- sideration and strict watch maintained against its appearance or reappearance. Infested trees should be sprayed with some stomach poison, such as a mixture of lead arsenate and water in the proportion of 2 pounds of powdered arsenate of lead to 50 gallons of water, or, in smaller quantities, 6 teaspoonfuls of the powder to 1 gallon of water. A knapsack, barrel, or tank spraying outfit, whichever is available and convenient to use, should give good results. Hand picking and dropping or shaking the larvae into pails partially filled with, kerosene, crushing them with the hands protected by leather gloves, and knocking or jarring them from the trees and treading on them, are all possible methods of control, especially where labor can be obtained cheaply. Such methods as these have been used successfully in Europe. ORGANIZATION OF THE UNITED STATES DEPARTMENT OF AGRICULTURE. November 12, 1923. Secretary of Agriculture Henry C. Wallace . Assistant Secretary Howard M. Gore. Director of Scientific Work E. D. Ball. Director of Regulatory Worlc Walter G. Campbell. Director of Extension Work C. W. Warburton. Weather Bureau Charles F. Marvin, Chief. Bureau of Agricultural Economics Henry C. Taylor, Chief. Bureau of Animal Industry John R. Mohler, Chief. Bureau of Plant Industry William A. Taylor, Chief. Forest Service W. B. Greeley, Chief. Bureau of Chonistry C. A. Browne, Chief. Bureau of Soils Milton Whitney, Chief. Bureau of Entomology L. O. Howard, Chief. Bureau of Biological Survey E. W. Nelson, Chief. Bureau of Public Roads Thomas H. MacDonald, Chief. Bureau of Home Economies Louise Stanley, Chief. Fixed Nitrogen Research Laboratory F. G. Cottrell, Director. Division of Accounts and Disbursements A. Zappone, Chief. Library Claribel R. Barnett, Librarian. Federal Horticultural Board C. L. Marlatt, Chairman. Insecticide and Fungicide Board J. K. Haywood, Chairman. Packers and Stockyards Administration [Chester Morrill, Assistant to the Grain Future Trading Act Administration J Secretary. Office of the Solicitor R. W. Williams, Solicitor. This bulletin is a contribution from Bureau of Entomology L. O. Howard, Chief. Forest Insect Investigations F. C. Craighead, Entomologist in Charge. 22 ADDITIONAL COPIES OF THIS PUBLICATION MAY BE PROCUEED FROM THE SUPERINTENDENT OF DOCUMENTS GOVERNMENT PRINTING OFFICE WASHINGTON, D. C. AT 5 CENTS PER COPY PURCHASER AGREES NOT TO RESELL OR DISTRIBUTE THIS COPY FOR PROFIT,— PUB. RES. 57, APPROVED MAY 11, 1922 V Farmers' Bulletin 1259 United States Depaicment oPAgricuttm-e / -./- / A SAV/Fiy INJURIOUS YOUNG PINiffl YOUNG PINES, l)oth nurseiy stock and natural reproduction, are often defoliated by larvae of Leconte's sawfly. Defoliation of young pines is usu- ally severe in its effects, killing, misshaping, or weakening the trees to such an extent that attacks of secondary enemies will kill them. This insect is common on the scrub pines through- out the eastern United States and is a constant menace to the better species in nurseries or reforest- ing areas. It can be controlled in nurseries and parks, when the infestation is heavy, by spraying with lead arsenate at the rate of 2 pounds of the powder to 50 gallons of water; or, if scatteringly present, by hand methods such as knocking the larvae from the trees and crushing them. In larger and less accessible areas, where it would be impractical to attempt control by spraying, rang- ers and lumbermen should make a practice of de- stroying the colonics of these larvae whenever they are found. Contribution from the Bureau of Entomology L. O. HOWARD, Chief Washington, D. C. January, 1922 A SAWFLY INJURIOUS TO YOUNG PINES. AVlLLIAJt MiDDLETON, Scientific Assistant, Forest Insect Invest iijations. The larva, or false-caterpillar, of an insect known as Leconte's sawfly^ is a serious enemy of pine in nurseries, parks, and reforest- incf areas in the eastern ITnited States. This insect shows a decided Fig. 1. — Young silver pine in nursery, completelj' defoliated by larviB of Leconte's sawfly. preference for j^oung trees and has demonstrated its ability to leave its local host and attack other species of pines. The effects of defoliation on j^oung pines (figs. 1, 2), especially before late summer, 1 Neodiprion lecontei Fitch ; ordor Ilymenoptera, suborder Chalastogastra, family Ten- thredinidae, subfamily Diprioninae. 3 75613°— 22 4 Farmers' Bulletin 1259. are usually severe, the part denuded often being killed. Trees not killed are frequently infested by secondary enemies which com- FiG. 2. — Young scrub pine on edge of woods, completely defoliated by larvae of Lcconte's sawfly. plete the work ; and, if by chance the trees recover, they are stunted or misshapen and of little or no commercial or ornamental value. Fig. 3. — Youug larvae of L'^outc'.-^ .^aw- fly, second and third stages. Four times natural size. A Sawflij Injurious to Young Pines. 5 APPEARANCE, LIFE, AND HABITS OF THE INSECT. The needles are eaten by small larvrei one-eif^litli of an inch lon^' when youn have three pairs of legs on the thorax and eight pairs of smaller legs on the abdomen, and the head has only a single pair of e}es, situated one at each side in a rather large, circular, blackish spot. The larva? are found clustered in colonies feeding on the pine nee- dles and occasional!}^ on the tender bark (fig. 5) of the young tAvigs. When full grown the larvae spin cocoons from which they emerge later as adults. Adult emergence is di- vided into two periods, a first issuance, brood A, and a second issu- ance, brood B. When the eggs are laid and hatch in the late spring or early summer, adults of brood A issue from the cocoons in the late summer and early fall of the same year; but adults of brood B from this batch of eggs do not issue from their cocoons until the late summer and early fall of Fig. 4. Larv;u of Lecontc's sawfly, fourth aud tifth stages. Four times natural size. 75613°— 22- 6 Farmers' Bulletin 1259. the followin*^ year, a complete colony developmental period of 14 months. If the eggs are laid and hatch in the late summer, adults of brood A of these eggs issue from their cocoons in the spring and early riG. -Terminal of young scrub pine showing defoliation and feeding work of larvaj of Lcconte's sawfly on Lark. Three-fourths natural size. summer of the following year, and adults of brood B of the same batch of eggs emerge from their cocoons in the late summer and early fall of the same year as brood A, making a complete colony developmental period of 12 months. (See diagram, fig. 6.) A Sawfly Injurious to Young Pines. 7 The cocoons (fig. 7) have been found several inches underground and only in this location; but it is quite possible that some larva^, os- YEAR I YEARH YEARH JUNE JULY fJUG. SEPT. OCT. />pff. M/jy JUNE JULY me. SEPT OCT. fiPR. Mfir JUNE JULY RUG. SEPX EGGS L/}Rl'^£ COCOONS /foairs SGGS - ij9f>l/flE COCOONS fiOULTS ■ - EGGS Lfiffme COCOONS ODULTS • ' "" "* ' ' ' Fig. 6. — Chart showing life and soasoiial history of Leconte's sawfly through the active period of throe years (November to March omitted, the insect being in the cocoon during this period). l^ecially those the adults of which will issue before winter, may spin their cocoons in more exposed places, even on the pine twigs. The Fig. 7. — Cocoons of Leconte's sawfly : At left, unopened ones containing the insects ; at right, those from whicli adults have issued (emergence holes shown). The females issue from the larger cocoons and the males from the smaller ones. Approximately natural size. cocoons are tough, papery, red-brown, capsule-shaped cases, five- sixteenths to seven-sixteenths of an inch lonjr. 8 Fanners' Bulletin 1239. The udults (fi<^. N) are rather robust, four-winded insects. The male is bhick with reddish yellow lerrs and has beautiful feathery feelers, or antennae. The female has the head and first two thoracic segments reddish brown and the third thoracic segment and abdomen black. Her feelers are rather slender and not feathery. Fig. 8. — Lcconte's sawtiy : .1 , Adult fomalp : li, adult male. About eight times natural size. The sawflies get their name from the complicated egg-laying organ of the female. It is well named " the saw," having blades and teeth and being used exacth' as a saw when tearing into the leaves in cut- ting a pocket for the eggs. A Sawfly Injurious to Young Pines. 9 The eggs are laid in shoe-shaped pockets, or slits, in the needles. Usually, attacked needles occur in a cluster, each needle bearing a Fig. 9. — Needles of scrub pine showing eggs of Leconte's sawfly embedded in them. Much enlarged. number of eggs. The egg scars, or pockets, are rather easily seen, being yellowish on the dark green needles. (Fig. 9.) 10 Farmers' Bulletin 1259. DISTRIBUTION. Leconte's sawfly occurs throughout the eastern United States, the accompanying map (fig. 10) indicating localities from which the species has been recorded or specimens received. TREES ATTACKED. This species seems to have a preference for jack pine,^ red pine,^ and scrub pine,* each of which furnishes a local host in some part of the eastern United States through- out which the insect occurs. Its attack is not limited to these spe- cies, however, for it is also found on or recorded from white pine,^ K 7 i • '^V ^ ^^^' scotch pine,*' loblolly pine,^ shore rV \ ) l^Ov^\^\!'^ pine,^ silver pine," mugho pine,^" western yellow pine," longleaf pine,^^ Austrian pine,^^ and Amer- ican larch.^* PERIODICAL OUTBREAKS. Leconte's pine sawfly, like most insect enemies of forest trees, ap- pears and disappears periodically. For several years this species will be very abundant, then for a few years it will be rare. The cause for this periodic disappearance has not been determined, but the low records of parasitism indicate that some factor other than parasitism plays an important role. NATURAL ENEMIES. Eight species of insect parasites and an infectious disease have been found killing this sawfly. None of these enemies, however, has been found widely enough distributed or abundant enough to account for the periodic disappearance of the species, and it is certain that neither any nor all of these natural checks are sufficiently numerous or effective to justify disregard of the artificial control measures suggested. Fig. 10. — Map showing localities where Leconte's sawfly is known to occur. - Piniis banksiatta. ^ P. rcsinosa. * P. iHrginiana. ^ P. strobus. * P. fiylvesPris. 'P. taeda. ^ P. contorta. " P. monticoUt. '"P. m ugh us. ^ P. ponderosa. ^ P. palustris. '3 P. austriaca. " Larix americana. A Sawfty Injurious to Young Pines. 11 CONTROL. The control of Leconte's sawfly depends largely upon the extent and location of the infestation. In nurseries and parks, when the infestation is heavy, a thorough spraying with lead arsenate, 2 pounds of powdered lead arsenate to 50 gallons of water (or 6 teaspoonfuls to the gallon), will give good results. Spraying should begin when the larvae are first discovered. In a scattered infestation, hand picking or knocking the larvae from the trees and ^rushing them will be found more economical and at least as effective. In large areas of either natural or artificial reproduction control can not be generally practiced because of its expense; but rangers and lumbermen should make it a habit to destroy the colonies of these larvae whenever found. Whenever these insects are observed in any locality and control measures are practiced against them, it is important that the terri- tory be carefully surveyed for the following 14 months, since it is possible that some larva? may have escaped the treatment and have spun cocoons. This possibility makes watchfulness necessary over the entire colony period of the species in order that an emergence of adults from these cocoons may not reestablish the infestation. WAFHINGTOX : GOVERNMENT PRINTING OFFICE : 1922 U.S. DEPARTMENT OF AGRICULTURE FARMERS' BULLETIN No.l623 THE GIPSY MOTH AND THE BROVN-TAILMOTH THE GIPSY MOTH and the brown-tail moth are two very destructive enemies of tree foliage which have gained entry into this country from Europe. The gipsy moth has spread over a large part of New England, and isolated colonies have been found in New York State east of the Hudson River, on Long Island, and in New Jersey. The brown-tail moth has become established in many localities, embracing about one-third of the area of the New England States. Substantial progress has been made in exterminat- ing the gipsy moth in New Jersey, and many isolated infestations have been cleaned up in other States. During the last 10 years the brown-tail moth has been far less abundant than was previously the case, except in certain sections in the eastern part of the infested territory. The decrease has been due to such factors as heavy mortality during the winter, increase in the abundance of imported parasites, a fungous disease that attacks the larvae, and field control work including spraying operations. The States and the Federal Government (the latter through research conducted by the Bureau of Ento- mology and quarantine and control work conducted by the Plant Quarantine and Control Administration) are actively engaged in destroying these insects by the use of appropriate measures. The Federal Gov- ernment is chiefly concerned in preventing their spread, while the States aim to reduce the infesta- tions and prevent the defoliation of valuable trees in woodlands, orchards, and parks. The methods which have been found effective in destroying the insects, together with a brief state- ment of the progress that has been made, are set forth in this bulletin. This bulletin is a revision of and supersedes Farmers' Bulletin 1335, Controlling the Gipsy Moth and the Brown- Tail Moth. Washington, D. C. Issued December, 1930 H THE GIPSY MOTH AND THE BROWN-TAIL MOTH By A, F. BxiRGESS, Principal Entomoloyifit in Charge of Moth Work, Plant Quarantine and Control Administration CONTENTS The gipsy moth Introduction and spread Record of clean-up of outlying gipsy- moth colonies Qipsy-moth extermination project in New Jersey Life history of the gipsy moth Means by which the gipsy moth is spread Food plants of the gipsy moth Injury caused by the gipsy moth Effect of climatic conditions on the gipsy moth Native enemies of the gipsy moth Introduced parasites and enemies Methods of controlling the gipsy moth__ The brown-tail moth Introduction and spread Life history of the brown-tail moth Food plants of the brown-tail moth Injury caused by the brown-tail moth... The brown-tail moth — Continued. Native enemies of the brown-tail moth.. Introduced parasites and enemies Methods of controlling the brown-tail moth Organization and status of work against the gipsy moth and the brown-tail moth Maine New Hampshire Vermont Massachusetts Rhode Island Connecticut New York New Jersey Pennsylvania and Ohio Work of the Dominion of Canada Work of the United States Department of Agriculture Cooperative work. Page 27 28 29 29 29 30 30 30 30 30 30 31 31 31 32 THE GIPSY MOTH I INTRODUCTION AND SPREAD N 1869 a number of egg clusters of the gipsy moth {Porthetria dispar L.) were brought from France to Medford, Mass., by a French mathematician and astronomer, who seemed to have had a fanciful idea that he could cross this insect with silkworm moths and thus develop a hardy race of silk- producing insects. In the course of his rearing experiments some of the eggs w^ere accidentally lost or some of the caterpillars escaped, and he made at that time public acknowdedgment of this fact, evidently somewhat appreciat- ing the danger. It is clear now that the insect increased slowly and after 10 years seemed to have been noticed by local residents but was believed to be some native caterpillar. It was not until some 20 years after the introduction, namely, in the summer of 1889, that this insect became so abundant and destructive as to bring it into general public notice. At that time fruit and shade trees in the immediate region were completely defoliated and the caterpillars swarming into the houses became a very grave nuisance. This situation was so serious that the State of Massachusetts appropriated funds and delegated to the State department of agriculture the task of exterminating this pest. The area that was found to be infested covered about 359 square miles and the trees in many towns surrounding Boston were com- 2 FARMERS BULLETIN 16 2 3 pletely defoliated each season for a number of years. As the work continued, more effective methods of treatment were adopted and better results were obtained; consequently, during; the summers of 1898 and 1899 little defoliation could be found in the entire area and few specimens of the moth were located throuiihout the entire residential sections of the infested district. Careful examination indicated that the insect had been exterminated in some of the towns around the outside border of the originally infested district. In February, 1900, the w^ork was discontinued b}^ the general court because of the popular belief that the danger had passed, in spite of the advice of experts that the insect had not been stamped out. Within the next five years the insect increased enormously. Many of the towns and cities in the old infested district were overrun with caterpillars which completely defoliated the trees in many of the residential sections and thousands of acres of woodland were stripped of leaves during the summer. The situation became so serious and intolerable that in 1905 control work was resumed by the State of Massachusetts. In the meantime the insect had spread far beyond the original limits of infestation, over 2,224 square miles being in- volved in Massachusetts as well as a considerable number of isolated areas in Maine, New Hampshire, and Ehode Island. In 1906 an appropriation was made by Congress and the Secre- tary of Agriculture was authorized to take all possible measures, in cooperation with the States concerned, to prevent the spread of this pest. The insect had increased to such enormous numbers and had spread so rapidly that the utmost efforts of the Federal and State forces Avere only able to apply relief measures in the badly infested residential sections and partially retard the continued s})read of the pest. Efforts were made to prevent the shipment of the insect to uninfested localities by inspecting products that were likely to carry the insect. This phase of the work was greatly strengthened as a result of the enactment of the plant quarantine law by Congress on August 20, 1912.^ Since October of that year shipments from the infested district have been regulated by Federal quarantine. On account of the serious situation that was resulting from the continued spread and increasing damage caused by this insect, efforts Avere constantly being made to develop improved means of control. The process of manufacturing lead arsenate, which was first made and used in the gipsy-moth Avork in 1893, Avas perfected so that the cost of production Avas reduced and the product could be more ef- fectively applied. Spraying machinery and equipment were devel- oped to a high point of efficiency. Advantage was taken of the results of experimental work in carrying on the field operations, and the details of field management were constantly improved in order that the greatest possible A^olume of effective Avork could be done with the funds available. This pest is distributed by natui'al means, principally by the ncAvly hatched caterpillars being bloAvn by strong Avinds when accompanied 1 This act created the Federal Horticultural Board and gave authority for the establish- ment of Federal quarantines to prevent the spread of dangerous introduced insect pests and plant diseases. The act making appropriations for the Department of Agriculture for the fiscal year ended June 30, 1929, transferred the functions of this board, together with insect-control activities, to the Plant Quarantine and Control Administration. THE GIPSY MOTH AND THE BROWN-TAIL MOTH S by high temperatures m the spring. Under favorable conditions such caterpillars may drift a distance of 20 miles. In spite of the efforts that were made by the Federal Government and all the States concerned, the insect continued to spread. By 1914 it had covered the sontl.ern half of New Hampshire and extended as far east as Bangor, Me. On the west it had crossed the Connecticut River in Vermont and Massachusetts. Rhode Island and many towns in eastern Connecticut were found to be infested. During the war period conditions were most unfavorable for preventing spread. The loss of efficient personnel and constant turn- over of men, together with extraordinary increase in costs, made progress difficult. During this period weather conditions were espe- cially favorable for spread toward the west. By the fall of 1922, colonies were found in many towns in Vermont and west of the Connecticut River in Massachusetts and Connecticut, and an infes- tation was located in New York State adjoining the Massachusetts State line. Every indication pointed to the continued spread of the insect unless more intensive work could be done. As a result of this serious situation a conference was held in the office of the commissioner of farms and markets in Albany, Decem- ber 26, 1922, which was attended by representatives from all the infested States, the Dominion of Canada, and the United States Department of Agriculture. ^ The conference considered the entire subject of the prevention of spread of the gipsy moth and its con- trol, and adopted a resolution urging that sufficient funds be obtained by the States interested and the Federal Government, for the pur- pose of continuing and strengthening present control methods in the infested area, to do necessary scouting for the discovery and destruction of border infestations, to determine the location of the most practical place for a control zone, to take necessary steps to make control therein effective, and for the destruction of all infes- tations in and west of saict zone. In order to carry out this project legislation was passed by the State of New York in April, 1923, carrying an appropriation of $150,000 to be administered by the department of conservation of that State. Federal funds were also provided for the fiscal year beginning July 1, 1923, in order to bring about effective cooperation. The plan finally adopted, in cooperation with the New York De- partment of Conservation, was to locate a zone east of the Hudson River where clean-up operations would be centered in order to pre- vent westward spread of this pest. (Fig, 1.) The territory east of this zone was to be treated by the States concerned as far as their funds would permit, and their work was to be supplemented by liberation of imported parasites and other natural enemies of the insect by the Bureau of Entomology. Work in the New York por- tion of the area was to be financed by the State with such assistance as could be given by the bureau after covering the eastern part of the zone. This zone embraced an area of over 8,000 square miles extend- ing from Long Island Sound east of the Hudson River (excluding - THE GIPSY MOTH, AN IMMINENT MENACE TO THE FOREST AND SHADE TREES OF THE STATU OF NEW YORK. New York State Dept. of Farms and Markets, Agr. Bui. 148, 58 p., illus. 1922. 4 FARMERS BULLETIN 16 2 3 Westchester County, N. Y.) to the Canadian border, a distance of over 250 miles, and ranging in width from 25 to 30 miles. While much of the extremely rugged country in the Adirondack and Green Mountains was avoided in northern New York and in Vermont, as well as the Catskills and some of the rougher country west of the Connecticut River in Connecticut, there are areas, em- bracing the Berkshire Hills in western Massachusetts and some of the sipsy MOTff B4/?e/ee zo/v£ Figure 1. — Barrier zone in New England and >few York territory directly south and southwest of them in Connecticut and New York, where the terrain is extremely difficult. In 1924, owing to the number of infestations found in Massachu- setts and Vermont, and a vigorous colony that was located at Henrys- burg, Quebec, by the inspection force of the Dominion entomologists of Canada, the quarantine line was moved westward to embrace the whole of the State of Vermont and additional towns in northwestern Connecticut. A foreign quarantine regulatino; the movement of Christmas trees was made effective covering the southern tier of towns in the Province of Quebec. (Fig. 2.) Since that time, owing to the effectiveness of the clean-up work in the barrier zone, sup- THE GIPSY MOTH AND THE BROWN-TAIL MOTH plemented by a limited amount of scouting work carried on west of the zone as a precautionary measure, it has been possible to revise the area under quarantine and eliminate the area included in the zone. The Canadian quarantine was withdrawn July 1, 1928. (Fig. 3.) The danger of reinfestation of the barrier zone depends to a very large extent on the density of infestation east of the zone. The Figure 2. — Quarautined areas, 1924 following tabulation indicates the acreage defoliated by the gipsy moth east of the zone from 1924 to 1929, inclusive : Acreage defoliated by the (jlpny moth, 1924 to 1929, incUisi/ix Tear Acres 1924 825 1925 48, 560 1926 80, 822 Year Acres 1927 140, 920 1928 262, 514 1929 551,138 It will be noted that defoliation has been increasing rapidly in the area east of the barrier zone, and during 1928 and 1929 the insect 6 FAKMERS BULLETIN 1G23 was suiRciently abundant to cause some defoliation between the Connecticut River and the zone area. During the period covered by the tabulation, parasites and natural enemies of the gipsy moth have been scarce in most of the infested area, but in the summer of 1929 an increase was noted. On account of these conditions the control work done by the States and the cities and towns has been confined Figure 3. — Quarantined areas, 1928 chiefly to residential sections and to parks and street trees. Very little work has been done in woodland areas. More infestations were found in the barrier zone in 1928 after July 1 than during the entire previous fiscal j^ear, which made the problem of preventing the increase of the insect far more difficult and emphasized the im- portance of carrying on work in the territory east of the zone in order to make it possible to keep the zone free from infestations. As a result of the increase in infestation directly east of the zone, 7 towns in Vermont, 12 in Massachusetts, and 31 in Connecticut, em- bracing an area of 1,581 square miles, were added to the generally infested area under quarantine. THE GIPSY MOTH AND THE BEOWN-TAIL MOTH 7 During the latter half of 1929 and the first half of 1930 the num- ber of infested locations continued to increase in the barrier zone and additional funds were made available by Congress to carry on clean-up work. No action was taken, however, to provide for the examination of territory innnediately east of the zone from which most of these infestations originated and which furnish a source of constant supply of the insect so long as they remain untreated. The scouting work during the fall of 1929 and spring of 1930 resulte/V/£S Figure 6. — Map showing area in New Jersey infested by the gipsy moth in lOJl, indicating the density, of infestation and location "of isolated colonies THE EGGS The female gipsy moth deposits a cluster containing 400 eggs or more, which she covers with buff-colored hairs. Most of the egg clusters are laid during July and hatch about the time the leaves begin to appear the following spring. They are deposited on the under side of branches of trees, on tree trunks, under loose bark, or in cavities in the trunks or branches, and are sometimes placed on stones or rubbish and in a variety of situations where tlie}^ are con- cealed from view, As the female moths do not fly, o^^^ clusters are THE GIPSY MOTH AND THE BEOWN-TAIL MOTH 11 seldom found far from the food plant upon which the caterpillars developed. THE LARVAE The newly hatched larvae feed on the opening leaves, making small perforations. They grow rapidly and become full fed early in July. During this period they molt five or six times, and as they increaye in size they eat a larger proportion of the foliage, so that, if the infesta- 924 St:?ay^/5£ M/L£Sy. /97 SC?UJI/?£ M/LES LEGEND ill^/e£>? scoc/r£p /s^^-/92S ^^^£^ SCOOTED /92S-/323 Figure 7. — Map showing conditions of infested area in New Jersey in 1928, indicat- ing colonies and reduced area requiring intensive work tion is severe, trees may be stripped completely of foliage before the end of June. THE rt'PAB When full grown, the caterpillars shed their skins and transform to pupae, which are chestnut brown and provided with tufts of yellow hairs. They remain in this stage about 10 days, after which the adult insects emerge. 12 FABMEES BULLETIN 16 23 Figure 8. — Life stages of the gipsy moth : A, Female moth ; B aud F, pupae ; C, larvae or caterpillars ; D, male moth ; E, egg mass. All ahout three fourths natural size THE ADULTS The male moth is dark brown, with black wing markings, and flies well. The female is nearly white, with black markings on the wings, and because of the weight of the abdomen she does not fly. After mating, the females be- gin depositing eggs. The time of year when the different forms of the insect may be found in the field is shown in Figure 9. MEANS BY WHICH THE GIPSY MOTH IS SPREAD Eo;ir clusters of the gipsy moth deposited on trees, lumber, stone, or other products that are likely to be shipped, may be carried long distances and cause the establishment of new colonies of the in- sect. Spread in this way is prevented by inspection of such products before they are shipped. Caterpillars of this insect may be spread for limited dis- FlGUUE 0.- -Time of year when the different stages of the jipsy moth are present in the field THE GIPSY MOTH AND THE BROWN-TAIL MOTH 13 tances by being carried on moving objects, such as trains, horse- drawn vehicles, or automobiles. The danger of such spread is very slight if the roadways are kept free from severe infestation. New colonies are started principally by the spread of newl}' hatched cater- pillars. Experiments have shown that these caterpillars ma}^ be blown by the wind, if the temperature is high enough for the cater- pillars to be active, and the stronger the wind the greater the prob- ability of their being carried long distances. Caterpillars have been carried more than 20 miles in this way, and specimens have been caught in the air 50 feet above the ground, although probably they are carried much higher in the air. The temperature must range above 65° F. and the wind velocity must be 8 miles or more per hour, in order that spread of small caterpillars by wind may result. In recent years a new avenue for spread of the gipsy moth has de- veloped from the extensive use of the motor truck for long-distance hauling. Fortunately the material hauled is only occasionally of a dangerous nature, but chance of spread in this way is more or less constant. The popularity of automobile camping parties presents another source of danger, particularly during the vacation season. There is a growing tendency, however, to restrict such camps to municipal or semipublic grounds. Under these conditions the danger can be minimized by proper inspection. Warning posters are being used in sections where parties are likely to camp, instructing them to examine their effects carefully so that no taterpillars or egg clusters of the insect will be carried away. Many camps in the heavily infested area are inspected annually. FOOD PLANTS OF THE GIPSY MOTH The food plants most favored by the gipsy moth are apple, the different species of oak, gray birch, alder, and willow. In cases of bad infestation nearly all deciduous trees are injured to a greater or less extent, with the exception of ash. Hickory is not a favored food plant, although the foliage occasionally shows severe feeding. Chestnut w^ll not support the gipsy-moth caterpillars when in the first stage, and pine will not support them in the first two stages ; but if other food plants are present severe injury may result from feeding by the larger caterpillars. Beech and poplar are sometimes fed upon freely, and occasionally the trees are defoliated. The different species of spruce are more susceptible to attack than, the pines. INJURY CAUSED BY THE GIPSY MOTH Unless reduced in numbers by natural enemies, unfavorable cli- matic conditions, or the application of control measures, the gipsy moth is capable of causing enormous injury to tree growth. In the area of Xew^ England which has suffered most from this insect thousands of trees have been killed as a result of defoliation. (Fig. 10.) On manv areas the trees were cut before they were mature and the wood "'sold at a loss on account of damage caused by the insect. Apple and oak have been injured most, but pine and other coniferous trees mixed with deciduous growth have suffered severely. (Fig. 11.) 14 FARMERS BULLETIX 16 2 3 Figure 10. — Deciiluons trees defoliattil liy tlu' s^ivr^y muth Figure 11. — White pine, in a mixed growth, defoliated by the gipsy moth THE GIPSY MOTH AND THE SROWN-TAIL MOTH 15 Many oak trees which have been weakened severely as a result of defoliation by the gipsy moth and the brown-tail moth have failed to recover because of the attacks of certain wood-boring insects. The species which has caused most damage in this way is a beetle {Agrilus hilineatus Weber) known as the two-lined chestnut borer, the larva of which feeds beneath the bark of injured trees. EFFECT OF CLIMATIC CONDITIONS ON THE GIPSY MOTH Investigations have shown that extremely low temperature during the winter is fatal to eggs of this insect that have been deposited in exposed situations. From -20° to -25° F. is usually required to injure them sufficiently to prevent hatching, and if the clusters are protected by snow, ice, or other material, the eggs are not killed even at this temperature. After extremely cold winters many eggs fail to hatch. Evidence also indicates that abnormally early frosts in the fall injure freshly deposited egg clusters. During May, when the caterpillars are hatching, there are some- times long periods of cold weather accompanied by heavy rains. This condition, or the occurrence of severe frosts in June, occasion- ally causes the death of the least hardy caterpillars. NATIVE ENEMIES OF THE GIPSY MOTH Few insect enemies of the gipsy moth native to New England cause any noticeable reduction in its numbers. This is shown by the fact that from 1900 to 1905, when no systematic effort was made to suppress the insect, alarming injury resulted, and native insect enemies did not increase to any marked degree. The same is true of the work of native insect-eating birds. While they undoubtedly feed to some extent on gipsy-moth caterpillars, there is no case on record where they have been able to control the insect. The " wilt," a disease which attacks and kills the caterpillars and pupae, has probably occurred in this country for many years. During some seasons, particularly in badly infested areas, it causes the death of an enormous number of the caterpillars and is often an important factor in reducing the infestation locally. As a rule, this disease is more common in heavy infestations, where overpopulation of cater- pillars causes a scarcity of food. INTRODUCED PARASITES AND ENEMIES In 1905 an effort was made by the State of Massachusetts, in co- operation with the Bureau of Entomology, United States Depart- ment of Agriculture, to introduce the parasites and natural enemies of the gipsy moth from its native home in Europe and Japan. Since that time a large amount of parasitized material has been received nearlv every year, and as a result some promising natural enemies have become established in this country and are assisting in bringing about the control of the species. The enemies which have become established and are at present destroying the largest number of gipsy-moth caterpillars and pupae are the Calosoma beetle {Calosoma sijcophanta L.), two species of parasitic flies {Sfurmia scuteJJata Desv. and Compsilura concinnata Meig.), one 2826°— 30 3 16 farmers' BULLETIN" 162 3 of which attacks the brown-tail moth as well as caterpillars of many native insects, and two species of small wasplike flies {Apan- teles tnelanoscelus Ratz. and A. JacteicoJor Vier.), one of which likewise attacks the brown-tail moth. Two tiny parasites of the gipsy-moth eggs have also been introduced and colonized, one {Oencyr^tus kuvanae How.) from Japan and the other {Anastatus disparis Ruschka) from Europe. Several other parasites have been introduced and are established in this country; however, they have not increased sufficiently to be considered important factors in gipsy-moth control. Some addi- tional parasites have been imported during the last three years, but their value has not yet been fully demonstrated. The work of the natural enemies of the gipsy moth, including the imported parasites, the Calosoma beetle, and the wilt disease, has greatly reduced the numbers of the insect in many localities that are badly infested. It is hoped that when the enemies of the moth are present in larger numbers over the entire infested territory the insect will become much less destructive than at present. The records at the gipsy-moth laboratory at Melrose Highlands, Mass., indicate that the species of parasites introduced prior to 1923 increased gradually in the field until 1923, when they reached their greatest abundance, and the results of their work were very notice- able over much of the infested area. In 1924 the gipsy moth was rather scarce, and parasitism was low ; the following year it was still Ioav and did not increase much in 1926. In 1925 the gipsy moth began to increase rapidly in the older in- fested area, and although some of the parasites gained slightly in 1927 and 1928 they did not prevent the rapid increase of the moth. Until the natural enemies demonstrate greater effectiveness throughout the entire infested area it will be necessary to employ the best mechanical methods for restricting the spread and curtailing the increase of the gipsy moth. In the meantime further work is being done in foreign lands, particularly in central Europe and the Mediterranean countries, to determine the principal factors that are responsible for the periodical scarcity of the insect there and to take advantage of this knowledge for the purpose of developing more effective natural control in this country. METHODS OF CONTROLLING THE GIPSY MOTH GEN.ERAL METHODS Creosote. — One of the best methods of controlling the gipsy moth is to treat the egg clusters of the insect between August 1 and April 1 with creosote to which a small quantity of lampblack has been added. The material is sold by dealers in the infested region under the name of gipsy-moth creosote. It is applied with a brush and leaves a black residue on the clusters treated. Creosote may be ob- tained from nearly all the large hardware or seed stores in the in- fested district. Burlap bands. — Gipsy-moth caterpillars usually seek shelter during hot, sunny days, and if a band of burlap is attached to a tree (fig. 12), large numbers of them will crawl beneath it, where they may THE GIPSY MOTH AND TH?: BROWN-TAIL MOTH 17 be crushed each day. Ordinarily a strip of burlap about 8 inches wide is placed loosely around a tree trunk and a piece of twine is passed around the center and tied to hold it in place. After this is done the top part of the burlap is folded down so that a double shelter is made beneath it. The extensive use of these bands has been discontinued durino; the last few years, owing to the expense FKiUUE 12. — Burlap band ou tire with caterpillars beneath it involved and because of the fact that if the burlap bands are applied early in the season, before the brown-tail moth caterpillars have pupated, an excellent place is furnished for these poisonous cater- pillars to make their cocoons, and severe poisoning results to the workmen. If this method is to be used in areas where the brown- tail moth is abundant, the burlap should not be attached to the trees until after June 15, when most of the brown-tail moth caterpillars will have pupated. 18 FARMERS BULLETIN 16 23 Sticky bands. — Bands of a widely knoAvn sticky substance for tree banding, which may be obtained on the market, may be used on tree trunks after the bark has been scraped so that the material can be applied evenly in a thin layer with a paddle. The purpose of this band is to prevent caterpillars from ascending the trees, and if the egg clusters have pre- viously been treated, this is a very effective measure. Every week or 10 days during the cat- erpillar season a comb or other similar implement should be run over the band in order to prevent hardening of the sur- face and to bring up fresh, sticky material from the part of the band near the bark. (Fig. 13.) Placing these bands on the trees prevents the caterpil- lars from reaching the foliage; and as they usually mass in large numbers beneath the bands, conditions are favorable for wilt disease to develop, and the caterpillars often die in large numbers from this disease and from starvation. Gipsy moth tree-banding ma- terial."— This is a black, greasy substance which was prepared and tested by the Bureau of Entomology in cooperation with the Bureau of Chemistry. It is similar to the product known as " Kaupenleim " that has been used in the German forests for many ^^ears to pre- vent injury to t;he trees by caterpillars. It is applied with a special " gun " designed for the purpose. (Fig. 14.) The thick, narrow band left on the tree trunk prevents the cater- pillars from reaching the foliage. This material is cheap and effective and is easily applied because it is not necessary to scrape the trees before putting it on. 3 For full information concerning the preparation and use of this tree-banding material, apply to the gipsy-moth laboratory of the U. S. Department of Agriculture at Melrose Highlands, Mass. Figure 13. — Caterpillars on tree trunk below sticky band THE GIPSY MOTH AND THE BROWN-TAIL MOTH 19 Spraying. — The most effective spray nuiterial for the .gipsy moth is lead arsenate. It can be used either in the paste or powder form. More effective control is possible if a sticker is used in the spray. Fish oil or raw linseed oil is excellent for that purpose, as it binds the insecticide firmly to the foliage so that it is not removed l)y rain or heavy dew. If either of these stickers is used the quantity of poison can be reduced from 121/2 pounds to 10 pounds of paste lead arsenate or from 614 pounds to 5 pounds of powdered lead arsenate to each 100 gallons of water. Fisli oil is cheaper than linseed oil and is therefore to be preferred. Four fluid ounces of the oil is required for each pound of poison used; in other words, I14 pints of oil for 5 pounds of powder or 10 pounds of paste. In preparing the spray mixture, add the oil after the poison is well mixed with water in the tank and while the whole is being agitated. Continue the agitation while the spray is being applied. The best grade of fish oil, known as " light pressed," should be used, as the cheaper grades are not so satisfactory. Warning. — It is not safe to allow cattle to graze beneath trees after the spray has been applied. When there is danger of the spraj' drifting on buildings they should be drenched with water before and after the trees are treated. A garden hose can be used for this pur- pose. If the spray is allowed to dry, it will disfigure the painted surface. Spraying fruit trees with this mixture is not recommended if the fruit is more than half grown, as it is difficult to remove the spray residue. For small operations the ordinary orchard sprayer may be used with one or more lines of hose, depending on the pressure that is available. Nozzles of the Vermorel or Bordeaux type are satisfactory. In case large shade trees or valuable park or woodland trees are to be treated, the use of a high-power sprayer is more economical. The type that has given the most satisfactory results in the gipsy- moth work develops sufficient power to throw a solid stream of spray so it will drift through the trees. (See illustration on. front cover.) The nozzle is constructed so that the stream will break into a fine mist high in the air, and this results in very satisfactory and rapid work. With such a spra3'er it is unnecessary to use a small hose and climb trees, which is a slow and expensive operation. A satisfactory high-power sprayer for this work is equipped with not less than a 10-horsepower gasoline engine and a triplex pump capable of delivering at least 35 gallons of liquid per minute at a FiGLUE 14. — Applying troe-bandins material to protect the foliage from gipsy-moth caterpillars 20 FARMERS BULLETIN^ 16 2 3 pressure of at least 300 pounds. This machinery, together with a 400-gallon tank, should be mounted on a well-built truck. (Fig. 15.) High-grade 1-inch spray hose is required, and a nozzle pres- sure of 300 pounds or more is necessary, depending on the length of the hose and the elevation of the nozzle above the level of the sprayer. Machines that will develop 1,000 pounds working pressure are necessary in rough country where extremely long lines of hose are required. A machine of this capacity equipped with high-pres- sure hose will supply a hose line 5,000 to 6,000 feet in length. and spray satisfactorily at an elevation of 600 feet above the level of the spra3^er. By using a small device, which is attached to the nozzle and is known as a spreader, it is possible to spray low growth very satisf ac- P^iGUKE 15. — Iligb-powcr truck sprayer torily. Fruit trees can be treated very rapidly in this way. (A nozzle equipped with spreader is shown in operation at the left of the picture on front cover.) Tests have been made for several seasons with airships of both the heavier-than-air and lighter-than-air tjqoe, to determine whether infested woodland areas could be dusted satisfactorily and economi- cally by these means. This method has not proved entirely satis- factory for use on forest growth. The cost is high, and the dust does not adhere as well as liquid spray when an adhesive like fish oil is used. For certain low-growing crops that have a high annual value this method has given excellent results in some sections of the country. ilETHODS TO BE USED IN ORCHARDS The methods to be used for controlling the gipsy moth in orchards depend largely on the severity of the infestation. If only a few egg clusters are present in the orchard, the early spraying which is THE GIPSY MOTH AND THE BROWK-TAIL MOTH 21 applied for the codling moth after the blossoms fall will be found useful, provided the quantity of lead arsenate used is increased to 10 pounds of paste, or 5 pounds of powder, to 100 gallons of water. This spra}' should be especially effective if fish oil is added. If the infestation is more serious, a second spraying early in June, with a similar quantity of poison, but without fish oil, will be found very satisfactory. Where the infestation is severe, it will probably be necessary to creosote egg clusters in the winter and spray in the spring. Thoroughness is a prime essential if good results are to be obtained. All poor or hollow trees should be removed; and if badly infested woodland is near by, the orchard trees should be banded. Orchard infestations can be managed by following these methods, and it will not require much additional expense or a great deal of extra work to protect the trees. In making this statement it is assumed that the orchard is being cared for by up-to-date methods to protect it from the codling moth and other injurious insects and diseases, and it is not likely that these results can be brought about in neglected orchards or where the owners do not practice the best horticultural methods in handling their growing trees. METHODS ADVISABLE IN CITIES AND TOWNS The same methods that are used in orchards are applicable in cities and towns and for the treatment of park and shade trees. In certain instances it would probably be advisable to use tree-banding material or burlap, preferably the former, and to discontinue spray- ing in cases where the infestation is very light. If the infestation is bad, creosoting, banding, and spraying should all be used in their season, in order to bring the insect under control and reduce the numbers present to a minimum. In town or city work careful attention should be given to near-by woodlands or isolated trees, particularly if they are located on high elevations immediately outside the residential area, as colonies in such locations may furnish a supply of caterpillars which will be distributed by wind throughout the town after it has been cleaned. In lightly infested woodland areas spraying may be used exclusively for control, but when heavy infestations exist, a combination of the most effective measures is usually necessary. The method of handling the gipsy moth in any town, city, or park, or on private estates, should be based on the degree of infestation as determined by some one who is familiar with gipsy-moth work, if the best results are to be secured at a minimum expense. Much energy and money may be wasted in applying remedies unless their applica- tion is based on a thorough knowledge of exisiting conditions. An owner of an infested estate should have an examination made by some qualified person who can give reliable recommendations as to treat- ments. It should be borne in mind that conditions as to infestation vary from year to year, and this should be considered when plans for treatment are being made. CONTROLLING THE GIPSY MOTH IN WOODLAND Satisfactory control of the gipsy moth in woodland by the eniploy- ment of hand methods such as have already been mentioned is im- 22 FARMERS BULLETIN 16 2 3 practicable under present conditions, unless the tree growth is par- ticularly valued for purposes other than lumber. If the woodland is situated near a large city and occupies space that is likely to be utilized in a few years for building lots, considerable money may be expended to advantage in protecting the trees, as these will make the property much more valuable when the land is subdivided. Limited areas of woodland on private estates maj'^ be of sufficient value to the owners to justify a considerable expenditure for moth destruction. In all cases, however, the species of trees involved should be care- fully studied before a plan of work is adopted, in order that the expense may be reduced as much as possible. Unfortunately the difficulty of treating the woodlands in the infested area of New Eng- land is considerably increased by the fact that they are for the most part composed of numerous species in mixture. Figure 16. — Mixed deciduous and coniferous woodland before thinning Experiments have shown that most coniferous trees are not injured by the gipsy moth if grown in isolated pure stands; and if the growth is such that the trees can be thinned to a stand of immune species, no hand suppressive measures are necessary in order to prevent injury by this insect. Such lots will not be attacked by the brown-tail moth, as the larvae of this insect do not feed on conifers. If mixtures containing a large percentage of deciduous trees are to be protected from moth injury, the species involved should be care- fully considered before a decision is reached as to the best methods of treatment. Sometimes practical methods of thinning (figs. 16 and 17) can be adopted so that species will be left that are only slightly subject to injury by these insects. Experiments have shown that mixtures of chestnut, pine, red maple, ash, and hickory, regardless of the proportion of each species, are seldom injured by the gipsy moth. THE GIPSY MOTH AND THE BROWN-TAIL MOTH 23 In woodlands the oaks are the most favored food plant of this insect, and, unfortunately, the infested region abounds in large areas where these species predominate. At present tlicre seems to be no method aside from hand treatment which will prevent serious injury to oak woodland, but as a large part of such land consists of poor sprout growth, the amount of damage sustained is not always so great as it might at first appear. The greatest injury likely to be caused in such areas where oaks and gray birch abound is the dying of small pines or other valuable species which have been denuded by the caterpillars after the oaks and birches have been defoliated. This reduces greatly the chance that the sprout growth will be replaced by any species of value that can withstand gipsy-moth attack. Consideration is being given to devising some economical method for protecting and improving wood lots of this character at FiGunE 17.- -Samo wuotihuui alter Ki'owih luMnei-l liv ihe si|i^\ uiirth removed by thinning moderate expense. It is true that in considerable areas of oak woodland the trees, although not mature, could be utilized for small timber, railroad ties, or cordwood, and in cases of bad infestation such woodland should be promptly cut if the wood can be sold to advantage. On cheap cut-over or infested lands in many sections of the territory white or red pine might be planted to advantage, but as this involves considerable expense and as the crop can not be har- vested for a period of years, the question of the desirability of managing any wood lot in this way must, in the end, be decided by the owner of the property. If the practice common in some European countries of maintain- ing municipal or state forests were well developed in the New England States, it would be possible in a period of years to trans- form considerable areas of land which are now destined to be worth- less, and which form a favorable feeding ground for the gipsy moth, into well-managed forests of valuable growth. 24 farmers' bulletin 16 2 3 THE BROWN-TAIL MOTH INTRODUCTION AND SPREAD The brown-tail moth {Nygmla phaeorrhoea Don.) was first found in the United States in Somerville, Mass., in the summer of 1897, and was undoubtedly introduced several seasons previous to that time on imported nursery stock. The insect increased enormously, and as the caterpillars were particularly fond of the foliage of fruit and ornamental trees and shrubs, they became an unbearable nui- sance, particularly in residential sections. Not only Avas complete defoliation common in early summer, but as the hairs from the caterpillars caused serious poisoning to human beings, the presence of this pest became a veritable scourge in densely populated sec- tions. The insect extended its range very rapidly because the moths of both sexes fly freely. This species occurs in many sections of Europe and is frequently seriously injurious. The State of Massachusetts applied suppressive measures from the winter of 1897 until February, 1900, when this work was dis- continued as was the case with that against the gipsy moth. By 1905, when w^ork on the gipsy moth was resumed, the brown-tail moth was extremely abundant in eastern Massachusetts. It was also present in enormous numbers in Rhode Island, southern New Hamp- shire, and southeastern Maine. Not only did fruit and shade trees suffer defoliation, but large areas of oak woodland, particularly sprout growth, was completely defoliated. The insect continued to spread until 1915, when most of the area east of the Connecticut River, with the exception of a portion of northern New Hampshire and Maine, was heavily infested. Some infestation also existed in Vermont and west of the Connecticut River in Massachusetts and Connecticut. Suppressive work was carried on by the States and the Federal Government and the resi- dential sections were kept fairly free from this pest. The area now infested by the brown-tail moth is shown in Figure 3, and is much less extensive than the maximum limits to which it had previously spread. Unfavorable winter conditions, particu- larly in the northern part of the territory, coupled with the work of natural enemies and disease and the continuous repressive measures used in the residential sections, have caused a remarkable decrease in the abundance of this pest. Tlie insect has been found in Nova Scotia and New Brunswick, but the area of the infested territory has been greatly reduced there and it is only moderately abundant at the present time in sections of Nova Scotia. This pest can easily be shipped on woody plants, but general spread in this manner has been ]^revented by the strict enforcement of inspection and quarantine regulations. LIFE HISTORY OF THE BROWN-TAIL MOTH The different stages in the development of the brown-tail moth are shown in Figure 18. THE EGGS The female moth deposits a small cluster of eggs on the underside of a leaf. They are usually laid in July, and are covered with brown THE GIPSY MOTH AND THE BROWN-TAIL MOTH 25 Figure 18. — Different stages of the brown-tail moth : A, Winter nest ; B, male pupa ; C, female pupa ; D, cocoon in leaves ; E, young caterpillars on leaf : F. full-grown caterpillar; G, female depositing eggs on a leaf, and egg mass also on leaf; H, egg mass removed from leaf and with some of the eggs exposed ; I, male moth ; J, female moth. All about three-fourths natural size hair taken from the body of the female. August 15. Hatching begins about THE LARVAE The newly hatched larvae or caterpillars feed on the epidermis of the leaf. After molting once or twice they begin to construct a winter web. This is made by drawing together several terminal leaves and securely fastening them by silk which is secreted by the 26 FARMEES' BULLETIN" 162 3 caterpillars. The larvae from one or more egg clusters live and feed in common, and as cold weather approaches they retire to the web, in which they remain during the winter. In the spring these larvae leave the web as soon as the buds begin to develop and feed upon the bud scales and small leaflets. They become full grown about the middle of June. THK PUPAE After the caterpillars finish feeding they spin loose silken cocoons and pupate within them. These cocoons are sometimes constructed separately, but in many cases large numbers of them are spun in a single mass. About two weeks are spent in the pupal stage. THE ADULTS Emergence of the moth usually begins the first week in July. The adult brown-tail moth is pure white. The abdomen of the female is much larger than that of the male, but in both sexes the tip of the abdomen is covered with dark-brown hairs. These moths are attracted to strong light, such as electric arc lights ; and as they fly at night, it is often possible to secure many specimens around the arc lights in cities and towns during the first half of July. FOOD PLANTS OF THE BROWN-TAIL MOTH The caterpillars of the brown-tail moth commonly feed on the leaves of apple, pear, cherry, oak, and willow, and they are sometimes found in considerable numbers on other common deciduous trees and shrubs. They never attack conifers and are seldom found on hickory, ash, chestnut, or birch. Oak foliage is one of the favored foods of the brown-tail motli caterpillars in Europe and was severely injured in New England for a number of years after this insect became established there. It has not suffered in this way in recent years except in 192G and 1927, when large numbers of webs were found on oak trees and the cater- pillars caused considerable defoliation in some localities. INJURY CAUSED BY THE BROWN-TAIL MOTH The principal injury caused by the brown-tail moth is due to the feeding of the larvae in the spring. If the infestation is bad the caterpillars are often numerous enough to devour the leaves as fast as the trees are able to develop them. As the webs are made on the terminals, the growth of the trees is often severely checked. In severe infestations trees may be completely stripped (fig. 19), but as the larvae become full grown during the first part of June, there is usually an opportunity for the trees to produce new leaves before midsummer. The young larvae that hatch in August frequently skeletonize the leaves to a considerable extent. This does not dain- age the trees seriously, as the growing period for the season is nearly completed. The bodies of the caterpillars of the brown-tail moth are provided with poisonous hairs. A microscopic examination of these hairs shows that the edges are barbed in such a way that when they come in contact with the human skin and are pressed into the flesh, intense THE GIPSY MOTH AND THE BROWN-TAIL MOTH 27 irritation is caused. These hairs are hollow and contain a poisonous substance which acts on the blood corpuscles. This causes serious poisoning and severe irritation, accompanied by external swelling, which is known as the brown-tail rash. Persons differ consider- ably in their susceptibility to this poison, but many cases are reported each year in the infested region, most of which are more serious than those of ivy poisoning. Many camps and summer cottages, par- ticularly in wooded areas, can not be occupied with any comfort during the early summer if the caterpillars are abundant, on account of the poisoning due to these caterpillars. If clothing is hung on the line near badly infested trees the hairs frequently find lodgment and are brought into the houses, and severe poisoning may result later. ^' 4,:^ f ^ 'M^ S ^ 1 iX l<«inimihf\ H H O gj ^2 ^1 H. ^ H ^^1 Figure 19. — Apple trees defoliated by the brown-tail moth. Note the hibenialing webs" oD the twigs The browai-tail moth has been less abundant during the last three years than heretofore. There have been local infestations, however, where serious injury resulted, particularly in northeastern Massa- chusetts, southeastern New Hampshire, and southwestern INIaine, and in some of the river valleys in New Hampshire. NATIVE ENEMIES OF THE BROWN-TAIL MOTH One of the important native enemies of the brown-tail moth is a fungous disease {Entomophthora aullcae Reich.) which attacks the caterpillars, particularly in the spring. It was first reported in this country by Roland Thaxter in 1888. Like all diseases of this nature, the benefit derived from it is regulated largely by favorable or unfavorable weather conditions. This fungus sometimes works to a slight degree on the small caterpillars in the fall, and is found occasionally in the winter webs. As a rule, however, the greatest 28 farmers' bulletin 1623 mortality of caterpillars takes place in the spring, when the)^ are nearly full grown, and the pupae may, under the most favorable conditions, be almost completely exterminated. Native parasites and predacious insects have done very little to check the increase of the brown-tail moth. INTRODUCED PARASITES AND ENEMIES Some of the parasites {Apanteles lacteicolor Vier, and Ccnipsilura concinnata Meig.) that were introduced as enemies of the gipsy-moth caterpillars also attack those of the brown-tail moth freely, and one additional introduced species {Meteorus versicolor AVesm.) is an important enemy of the insect. The Calosoma beetle {Calosotna sycophanta L.), both in the adult and larval stages, destroys many brown-tail moth larvae and pupae. The parasites and natural enemies of this insect are more effective than is the case with the gipsy moth, and extremely low temperature in the winter often proves fatal to a large proportion of the small caterpillars in the webs. These factors, together with the enormous amount of hand suppres- sion that has been employed in many parts of the infested area, have resulted in a pronounced decrease in the abundance of the insect during the last few years. METHODS OF CONTROLLING THE BROWN-TAIL MOTH The brown-tail moth can be controlled by cutting off the winter webs and burning them before the caterpillars begin to emerge in April. These webs should be destroyed by fire, for if they are simply cut from the trees and left on the ground, the caterpillars will emerge, and no benefit will result from the work which has been done. In orchard practice it is sometimes inadvisable to cut the winter webs, for where an infestation is bad the cutting is likely to leave poorly shaped trees. Spraying in the spring is not a satisfactory remedy unless the infestation is very light, because the caterpillars, when they occur in large numbers, do not allow the tree to put out sufficient foliage to hold the spray material. The most effective method in orchards is to spray the tree's before the midde of August, using 3 pounds of leacl-arsenate powder to 100 gallons of water. Before spraying operations of this sort are at- tempted the orchardist should determine to what extent the trees are infested with egg masses of the brown-tail moth. If the infestation is very slight, it will be more satisfactory to cut and destroy the webs. If the infestation warrants, both shade, ornamental, and fruit trees may be sprayed to advantage at this time. Caution should be used, however, in spraying fruit tree's, particularly if early-fall va- rieties are to be .treated. The foliage should be treated, particularly the terminal shoots, and as much care as possible .should be exercised not to cover the fruit. Late fall or winter varieties of fruit may be sprayed with lead arsenate in August, and although an occasional spot may be found on the fruit at the time of picking, no injury will result from it. In ca'ses where only a few choice fruit trees are sprayed it is practicable to wipe the fruit before packing for sale ; THE GIPSY MOTH AND THE BROWN-TAIL MOTH 29 but this will not be necessary if care is taken to spray only the termi- nal growth of the trees, as this is where the bulk of the egg clusters are deposited. The damage caused by the brown-tail moth is ordinarily not so feevere as that resulting from gipsy-moth infestation, because the brown-tail moth does not have so wide a range of food plants and, further, because the bulk of the feeding by the larvae is done early in the season, so that the trees have an opportunity to recover before midsummer. In the territory where both insects exist the caterpil- lars of the gipsy moth supplement the feeding which has been done by those of the brown-tail moth, and the injury is, therefore, greatly increased. During the last few years this insect has seldom been found feed- ing on oak foliage, except in the worst infested localities, and elm, maple, and rose are not as badly infested as was the case about 15 3'ears ago. Thorough destruction of brown-tail moth webs in residential sec- tions and in orchards has resulted in materially decreasing the insect in thickly settled sections. Elimination of worthless apple and wild cherry trees would help gi'eatly in reducing the pest. ORGANIZATION AND STATUS OF WORK AGAINST THE GIPSY MOTH AND THE BROWN-TAIL MOTH Each State infested with these insects i's carrying on control work, and many of the towns and cities are similarly engaged. The Dominion of Canada and several of the Provinces have taken up control and eradication work. MAINE In Maine the work is in charge of the commissioner of agriculture, who has authority to appoint assistants to take charge of the opera- tions. In the southwe'stern part of the State the gipsy-moth infes- tation is general and in places severe, but the greater part of the known infested area is only slightly infested. The severity of infes- tation increased in 1926 and 1927, and many heavily infested sections were found in 1928. The brown-tail moth is not now seriously abundant except along the seacoa'st in the southwestern part of the State. Over 12.000 square miles of territory are infested with the gipsy moth and about 7,000 with the brown-tail moth. The former has gradually spread to new territory, but the area infested by the latter has decreased considerably since 1919 and has not changed very greatly for several years. NEW HAMPSHIRE The moth work in New Hampshire is in charge of the State ento- mologist. Over 8,000 square miles are infested with the gipsy moth and about 4.000 with the brown-tail moth. Most of the territory south of Lake Winnepesaukee has suffered severe and repeated de- foliation. In 1927 the largest defoliated areas centered around the lake and tov.ard the east and northeast. In 1928 severe defoliation was general throughout the section east of the Merrimac River and to the foothills of the White Mountains. Serious stripping also occurred west of the river in the southern part of the State. 30 farmers' bulletin 16 2 3 VERMONT In Vermont the moth work is in charge of the commissioner of agriculture, who appoints an entomologist to carry on the field work. About 6.000 square miles are infested by the gipsy moth, the worst localities being along the Connecticut River. An occasional web of the brown-tail moth has been reported in recent years, but this insect does not appear to maintain itself in numbers in the State. MASSACHUSETTS The commissioner of conservation has charge of the moth work in Massachusetts. Each infested town is required by law to select a local superintendent, whose appointment must be approved by the commissioner. Owners are required by law to keep their property free from these pests, but can not be compelled to expend for this purpose more than $5 per year on each $1,000 assessed valuation. Towns and cities must expend funds for proper treatment of the street trees and those in parks and on public grounds. After the amounts fixed by law are expended, financial aid may be supplied by the State. The gipsy moth at present occurs to a greater or less extent in every town in the State east of Berkshire County. It has increased in abundance over much of the infested area during the last three years. The area infested by the brown-tail moth has been reduced so that at present it amounts to only a little over 4,000 square miles. RHODE ISLAND In Rhode Island the commissioner of agriculture has charge of the moth work, which is done under the supervision of the State en- tomologist. The gipsy moth occurs in all towns in the State, and several heavy infestations were treated during 1927 and 1928. The brown-tail moth infestation has decreased rapidly in recent years, and at present none of the towns are known to be infested. CONNECTICUT In Connecticut the work is in charge of the State entomologist. The brown-tail moth has not been found in this State for several years. The gipsy-moth area now occupies about 3,000 square miles. Control work has heretofore been effective in controlling the insect, but during the past two years the infestation has been increasing somewhat in the eastern part of the State. NEW YORK In New York State the field work against the small number of scattered colonies that had been found up to March, 1923, was su- pervised by the director of the bureau of plant industry, of the department of farms and markets. At that time the work was transferred to tlie department of conservation, which has worked co- operatively with the Bureau of Entomology in the New York section of the barrier zone. NEW JERSEY In New Jersey the State work is under the control of the State department of agriculture. The funds appropriated have been used in conjunction with Federal funds, and the direct supervision of the work has been in the hands of the United States Bureau of THE GIPSY MOTH AND THE BROWN-TAIL MOTH 31 Entomology. The results, up to the present time, have been very satisfactory. PENNSYLVANIA AND OHIO Work on one small colony in Pennsj'lvania and another in Ohio was done by arrangement with the State officials — in Pennsylvania with the bureau of plant industry of the department of agriculture of that State and in Ohio with the State nursery inspector. The results were satisfactory, as both colonies of the insects have been exterminated. V^ORK OF THE DOMINION OF CANADA Work on the gipsy moth and the brown-tail moth in Canada is conducted by the division of foreign pests suppression of the office of the Government entomologist. Cooperation with the Provincial governments of New Brunswick, Nova Scotia, and Quebec has been maintained. The brown-tail moth is not now known to occur in the Province of New Brunswick but is found in decreasing numbers in the Annapolis Valley in Nova Scotia. The gipsy-moth colony found at Henrysburg, Quebec, has been exterminated through the efforts of the Dominion and Provincial officials, and the insect is not known to occur in Canada at the present time. WORK OF THE UNITED STATES DEPARTMENT OF AGRICULTURE The gipsy-moth project has for many years been conducted by the Bureau" of Entomology. On July 1, 1928, the quarantine and control work was transferred to the Plant Quarantine and Control Administration, and the research work was assigned to the Division of Forest Insects of the Bureau of Entomology. The object is to control and prevent the spread of these insects. For a number of years it was believed to be quite impossible to restrict the spread of the brown-tail moth on account of the heavy migration of the adults of this species. In recent years, owing prin- ::il)ally to the effectiveness of parasites introduced by the bureau, win- ter conditions unfavorable to the insect, and in some sections the effec- tiveness of a fungous disease which attacks the caterpillars, in addi- tion to a large amount of hand suppression work, it has beeii possible not only to prevent spread but to record a marked reduction in the infested area. In certain sections near the seacoast in New Hamp- shire and northern Massachusetts and near some of the rivers, how- ever, rather heavy infestations exist. One of the dangers in con- nection with the brown-tail moth at present is that favorable climatic conditions or temporary scarcity of natural enemies may enable it to increase rapidlv and spread proportionately. The gipsy moth was held in check for several years and did not spread beyond the Connecticut River. During the war period, when extreme difficulty was experienced in maintaining a field force on an effective basis, and funds were inadequate to meet the increased cost of operation, infestations developed lapidly, and strong winds imme- diately following the hatching period caused an extensive spread of the insect to the west and northwest. Field work indicated that many colonies were established during that period, as scattered in- festations were found in the Berkshire Hills section of Massachusetts and Connecticut and in the Green Mountain region in Vermont. 32 farmers' bulletin 162 3 This territory is extremely rugged and very difficult for field opera- tions. The establishment of the barrier zone has already been discussed in some detail, and the results secured thus far have justified the effort expended. A large amount of experimental work has been done to devise better methods of controlling these insects. Natural enemies have been introduced from Europe, northern Africa, and Japan and colon- ized throughout most of the infested area. Specialists have spent considerable time studying the insects in their native homes and collecting parasites for shipment to this country. This phase of the work is being pressed as rapidly as possible. Investigations looking toward the planting and growing of forest trees that are not subject to attack by the gipsy moth are being continued. The entire area known to be infested by either of these insects is under quarantine, and shipments o.f nursery stock, lumber, cordwood, and other forest products, including Christmas trees and greenery, and stone and quarry products are not permitted to leave the terri- tory unless they are inspected and accompanied by a certificate stating that they are free from infestation. COOPERATIVE WORK Since the gipsy moth and brown-tail moth work was begun by the Bureau of Entomology more or less work has been done in coopera- tion with the States concerned. The introduction of parasites and natural enemies of the gipsy moth was conducted in cooperation with the State of Massachusetts for several years, x^fter the infesta- tion had covered large areas in other States an arrangement was made for this work to be carried on by the Bureau of Entomology. The general plan of field work in New England is for the States to manage the clean-up east of the barrier zone while the Federal forces work in the zone and cooperate in making the entire work effective. In New York the barrier zone work is handled in cooperation with the State authorities. The work in New Jersey is planned with the purpose of extermi- nating this large infestation, and close cooperation with the State has been maintained. The gipsy moth and brown-tail moth quarantine covers the entire infested area, and its enforcement has thus far prevented long-dis- tance spread of these pests. ORGANIZATION OF THE UNITED STATES DEPARTMENT OF AGRICULTURE WHEN THIS PUBLICATION WAS LAST PRINTED Secretary of Agriculture Arthur M. Hyde. Assistant Secretary R. W. Dunlap. Director of Scientific TTorfc A. F. Woods. Director of Regulatonj Work Walter G. Campbexl. Director of Extension Work C. W. Warbukton. Director of Personnel and Business Admin- W. W. StockbeeGeb. istration. Director of Information M. S. Eisenhowe2i. Solicitor E. L. Marshall. Weather Bureau Charles F. Marvin, Chief. Bureau of Animal Industry John R. Mohler, Chief. Bureau of Dairy Industry O. E. Reed, Chief. Bureau of Plant Industry William A. Taylor, Chief. Forest Service R. Y. Stuart, Chief. Bureau of Chemistry and SoiU H. G. Knight, Chief. Bureau of Entomology C. L. Marlatt, Chief. Bureau of Biological Survey Paul G. Rbtiington, Chief. Bureau of Public Roads Thomas H. MacDonald, Chief. Bureau of Agricultural Economics Xils A. Olsen, Chief. Bureau of Home Economics LotnsE Stanley, Chief. Plant Quarantine and Control Administration- Lee A. Strong, Chief. Grain Futures Administration J. W. T. Duv'el, Chief. Food and Drug Administration Walter G. Campbell, Director of Regulatory Work, in Charge. Office of Experiment Stations , Chief. Office of Cooperative Extension Work C. B. Smith, Chief. Lilyrary Clabibel R. Babnett, Librarian. 33 U. S. GOVERNMENT PRINTING OFFICE: I9S0 For sale by the Superinteoaent of Documents, Washington, D. C. Price 10 cents BULLETIN OF THE UMMIMOfAffldTII No. 170 Contribution from the Bureau of Entomology, L. O. Howard, Chief. J February 9, 1915. THE EUROPEAN PINE-SHOOT MOTH; A SERIOUS MENACE TO PINE TIMBER IN AMERICA. By August Busck, Entomological Assistant, Forest Insect Investigations. INTRODUCTION. One of the most injurious insects to pine forests in Europe is a small orange-red moth, the larva of which eats out the new buds and kills or deforms the young twigs of pine trees, so as seriously and permanently to lower their timber value. This European pine- shoot moth, which is known under the scientific name Evetria huoliana Schiffermiller, has within very recent years been accidently intro- duced into America on imported European pine seedlings and has unfortunately become established in several widely separated locali- . ties in the eastern and middle western States. -•Av.axr.*'**' Early last summer (1914), a correspondent of the Bureau of Entomology complained of a serious insect injury to European pines under his surveillance on Long Island, and sent examples of the injury and of the larvse causing it ; the latter could not be identified as those of any of our known American pine pests, and the writer was therefore authorized to visit the affected localities in order to ascertain the extent of the injury and to obtain sufficient live ma- terial for study and rearing. From this material a large number of moths emerged during the latter part of June and these were at once recognized as the famous European pine-shoot moth. Subsequent surveys, undertaken by the bureau through Mr. Carl Heinrich and the w^riter, established the fact that the species has been repeatedly introduced on European nursery stock, and that it has be- come established in nurseries and parks in several localities scattered over nine States. In view of the experience with other introduced European insects, and considering the very serious financial loss caused abroad annually by this insect, its introduction into this country gives just cause for alarm, because incalculable injury may result to the vast American forest interests if this insect is permitted to become generally estab- lished on our native pines. 71551°— 15 2 BULLETIlSr 170, U. S. DEPARTMENT OF AGRICULTURE. Some idea of the extent and permanent character of the injury which this insect is capable of inflicting may be gained from the illustration (PL I) of a European pine forest which has been infested by it for several years in succession, with the result that a majority of the tree trunks are so twisted and crooked that their value as tim- ber is materially lessened, HISTORY OF THE SPECIES IN EUROPE. The species is a constant menace to pine forests in Europe and an- nually causes serious depredations, especially to young plantations of pine, in spite of continual preventive work against it. It has been the subject of much study and of an extensive literature from the time it was first described by Schiffermiller in 1776 to the present day. The species was named in honor of a Vienna entomologist, Baron Buol, who studied its injurious work during the latter part of the eighteenth century ; since then numerous accounts have appeared of particularly severe outbreaks in many parts of Europe, from England to Eussia, and from Scandinavia to southern France. It also occurs in Siberia. One such outbreak in Denmark, in 1805-1807, is recorded by Nie- mann (1809).^ This was so serious as nearly to cause pine culture to be abandoned in that country as hopeless. It is interesting to note that at that time the same preventive means were resorted to as are now employed against the insect, namely, the wholesale pruning and burning of all infested twigs. The German forest entomologist, Ratzeburg, counted Evetria huoliana one of the most injurious forest insects and gave a detailed account (1840) of the life history, structure, and economic impor- tance of the species. He mentioned especially an unusual outbreak in 1836-1838, which covered many parts of Europe. In the province of Furstenau the Rochesberg Mountain, which was covered with pines, became so seriously infested that it was under consideration by the authorities to burn it off and plant new trees. Other localities were only saved by strenuous systematic collecting of the infested twigs; thus, in the small province of Kesternich alone, 150,000 larvae were gathered and destroyed. Judeich and Nitsche (1895) state that the injury caused by Evetria huoliana is often fatal to the pine plantations. To quote from these authors, " If the attack is slight, it results in the branching of the tree, but if the attack is more severe and continued for several years, as we have seen it, then hardlj?^ an}^ bud is spared and the pines become stunted into miserable small bushes from which numerous 1 Dates in parentheses refer to " Literature," pp. 10-11. THE EUEOPEAN PINE-SUOOT MOTH. 3 branched shoots and hirge needle tufts stick out." These authors record many severe outbreaks and mention especiall}" one in 1883- 1885, in the Royal Forest Reserve, Pillnitz in Saxony, where nearly 75 acres of young pines planted in 1878 became infested to such an extent that hardh' a shoot was spared, and in 1884 the entire planta- tion presented a pitiful, crippled appearance. J. E. V. Boas (1898), who has made original investigations of the insect in Denmark, considers it one of the most injurious insects affecting forest trees. Among other outbreaks he mentions one in Jutland, Denmark, extending through several years around 1870, which " threatened the total destruction of the pine plantations." The Belgian authority on forest insects, G. Severin (1901), regards Evetria huoliana as the most injurious insect to pines in Europe, and emphasizes the lasting injury to the timber resulting from even slight attacks of this insect. All other European handbooks on entomology or on forestry con- tain similar accounts of this insect and express the same opinion as to its destructiveness to pine. FOOD PLANTS. Evetria huoliana is confined to pine and does not attack other coniferous trees, as spruce or larch, even though these grow along- side of the infested pines. A\Tiile the species is most often men- tioned on the yellow pine, or Scotch pine,^ in Europe, because this is preeminently the forest tree of importance there, it attacks all sjoecies of Pinus indiscriminately, according to Ratzeburg and other authori- ties, and the American infestations have come in on European seed- lings of the Austrian pine - and on mughus pine ^ quite as often as on Scotch pine. According to Ratzeburg and Severin, it also attacks and is equally injurious to American white pine,* which is cultivated in Europe; and Mr. Carl Heinrich found the species on a small lot of another native American pine," which was growing immediately surrounded by infested European pine seedlings. These latter records are particularly significant, as they prove be- yond question that the pest will spread to our native American pines if not prevented. The species attacks mainly young trees between 6 and 15 years of age, but it is often excessively destructive to younger plantings and seedlings and injurious also to older trees, though trees of 30 years or older are rarely serioush' affected. ^ Pinus sylvestris. * Pintis sirohtis. ^ Pinus laricis vav. austtiaca. ^ Pinus resinosa. ^ Pinus montana var. mughus. 4 BULLETIN 170, U. S. DEPARTMENT OF AGRICULTURE. INTRODUCTION AND DISTRIBUTION IN AMERICA. American nurseries have imported many thousands of pine seed- lings annually from Europe, especially from France, Belgium, Hol- land, Germany, and England. Importations normally take place in the fall, winter, and early spring. At this time of the year the young larvae of the pine moth lie dormant within the buds, so that an infestation is easily overlooked. It is evident that the pest has been present in a number of shipments of late years and that it thus has been introduced repeatedly into American nurseries. In a great majority of these cases, however, the species has been unable to estab- lish itself and has died out during the first year. Many of the larva3 die from overheating en route, or from various other unfavor- able circumstances incident to the handling and transplanting of the seedlings under cliiferent climatic conditions. Only by a combina- tion of favorable conditions would the few surviving larvae have been able to develop into moths and succeed in establishing the species in this country. This is probably the reason why the species as yet has become established in comparatively few American localities. It appears that such established infestation has taken place only in very recent years and especially within the last two years, or since the demand for European pines has become general. Up to the present time the European pine moth has been dis- covered in only 32 nurseries and private estates, representing 20 localities in 9 States, namely : state. Locality. Discovered in- Illinois Chicago Private grounds. One nursery. Do. Do Do Dundee Do Western Springs Do. Do Do. Do Kenilworth Two private grounds. One nursery. Do. Do Bloomington . Ohio Tippecanoe City West Virginia Elm Grove Do. Pennsylvanift Pittsburgh Private grounds. One nursery. Do Philadelphia New Jersey . . Somerville New York Do One niu-sery and one estate. Do Massachusetts Dedham One nursery. Do. Do Do Do. Connecticut Do. Rhode Island Newport . . In none of these localities, except on Long Island, has the species existed for more than the last two years, and in most of them it has become established only within the last year. But the survey for this insect has so far covered only about 60 localities, which could be reasonably suspected to harbor the pest because it was known that importations of European seedlings had Bui. 170, U. S. Dept. of Agriculture. Plate I. Work of the European Pine-Shoot Moth (Evetria buoliana). Section of European pine forest showing deformations in the trunk of Piiuis i-i/lrcatris resulting from several consecutive years' injury. (After G. Severin.) Jul. 170, U. S. Dept. of Agricultur Plate II. Stages of the European Pine-Shoot Moth. Moih iuxl full-grown larva; both greatly enlarged. (Original.) [Drawings by IMiss Mary Oarmorly.] Bui. 1 70, U. S. Dept. of Agricultur Plate III. I- ^ O "• O 2 z o 0. ^ ^ o Bui. 1 70, U. S. Dept. of Agriculture. Plate IV. M"^.' WUUStuljn ■^i/^ \iVSm!m^'^ v^ffi^^ :^^^^svaH^^y^^ ' ""■^^^S^^p^^f^^^U^^ : V^'is^wfesM^^^*' W^l^ 4A# ^ w^ma^^m ^- '"-3! ^t^^fv^^^'"'' ^1 ^^^■k^^ ^^J '■^'^\^ %^^''^ w^ y^^^^ "^^^3;'^ ^^.^^''^L^'MM ^-7- ^^^^^ y^^:^^ m >'-*¥•■ z^- : - _ • ■- •, --^^^ -' ^^S^'"~- ^^- "^B^DE ' ^»?rij^ -'"■ '-> ^ — "^i "^^ ^ Work of the European Pine-Shoot Moth. Malformations in pine resulting from injury by this pest. (C»riginal.) Bui. 170, U. S. Dept. of Agriculture. Plate V. r ^ ^ 'l Bui. 170, U. S. Dept. of Agriculture. Plate VI, v.<^ ^^IQI^^^^H ap#-; "*i P^ ^k 'ty^' ^^^^^Sm^Sm l^^^^^^^^lH^^PBly %',%;<,... ••^P^P^ THE EUROPEAN PINE-SHOOT MOTH. 5 taken place, and the indications are very strong that the pest has be- come established in several other widely distributed localities, either by direct importation from Europe or by distribution from infested American nurseries. This is particularly to be suspected of locali- ties where large importations and plantings of European pines have been made. As yet the pest has been found only in nurseries and private parks supplied by these infested nurseries. In no case has it yet been found on forest trees in America. The species is therefore at present mainly a nursery problem in this country and consequently may yet be controlled and possibly even eliminated by proper measures under Federal and State supervision. That this condition can not long endure and that the pest, if not ciiecked, will soon multiply and spread to native p)ines outside of nurseries and pass beyond the pos- sibility of elimination is clearly indicated by all the evidence on hand. LIFE HISTORY. In Europe the moths (PL II, upper figure) issue in July, some- times as early as the end of June, and in the warm evenings they swarm around the pines in large numbers. During the day they sit quietly on the branches, as can be ascertained by giving the tree a sharp jolt, which will cause the moths to fly out. When the insect sits still on the food plant it is not easily discovered, for the apparently striking orange-red color blends well with the natural surroundings and therefore must be classed as a protective coloration. Early in August the eggs are laid singly on the new buds for next year's growth, the terminal cluster of buds being nearly always chosen for oviposition. The young larva soon hatches and eats its way into the bud, making itself a roomy cell by devouring the live inside part. It attains a length of only a few millimeters during the fall months, and overwinters within the hollow bud. At this stage its presence is easily overlooked, though a trained eye will discover a small exuda- tion of pitch over the entrance hole differing from the normal exuda- tion of the buds. (See PL III.) In May, as soon as the sap begins to rise in the trees, the larva the buds. (See PL III.) leaves its winter quarters and bores into the bud next thereto, in turn destroying this and as many others as it needs for food. As the remaining buds adjoining begin to grow into young shoots the larva attacks them. It eats the entire inside of the youngest shoots and these consequently die. The more developed shoots are injured only on one side, and these sometimes continue to grow, but are bent downward at the injured spot. The larva (PL II, lower figure) feeds only on the soft growth on which the needles have not yet appeared, and by the time the needles have developed all, or nearly all, of the shoots in the infested cluster have become dead or injured. The 6 BULLETIN 170;, U. S. DEPARTMENT OF AGEICULTUEE. larva then makes a silk-lined chamber within one of the hollow shoots and here it pupates. After about three weeks the spiny pupa j)ushes itself half way out through the dry wall of its chamber and the moth, or adult, issues. The full life history of the species in America has not been ascer- tained, because a full year has not elapsed since it was first dis- covered here. While in the main it is the same as in Europe, a very distinct difference has already been noticed, due to the longer and warmer summer and fall in this country. In Europe the young larva attacks only one bud and attains very little growth before it enters the dormant winter season, but in the warmer climate of America the larva eats out two, three, or more buds and attains nearly half of its growth before winter. This, of course, tends to make the species even more injurious here than it is in Europe. AVliile it is altogether probable that the species has here only one generation annually, as in Europe, the possibility is not absolutely excluded that on account of the longer season it may eventuall}^ de- velop two generations annually like the allied native species. This, of course, would greatly increase its power for injury. CHARACTER OF INJURY. During the entire spring the infested twigs are very noticeable by reason of the dead and injured buds and young shoots, and the empty pupa skin sticking out of the destroyed shoot is also a familiar and easily noticed sight during the summer months ; but the extent of the injury caused by this insect is only realized later in the season, when the new growth is found to be either quite destroyed or perma- nently injured. As may be gathered from the foregoing account of the life history, each one of these insects does very considerable damage, not only by destroying a large number of buds and young shoots but by injuring the adjoining shoots which remain and which normally should sup- plant the destroyed leaders ; thus the trees are permanently disfigured. These injured shoots bend downward and outward and afterwards grow upward again in a curve, in the attempt to continue the normal upward growth of the tree. This results in a characteristic malfor- mation (Pis. IV, V, VI), so familiar in European pine forests that it has a popular name in each country — as " posthorn " and " waldhorn " in Germany and Holland and " baionnette " in France, while the few examples which have so far occurred in America have suggested the name " Dutch pipe " to those who have noticed it. This injury does straighten out somewhat during the successive years' growth, but never can be fully remedied and will always be noticeable and a seri- ous detriment to the timber (PI. I). Injury of this character is the result even when the species is present in only small numbers, the THE EUROPEAN PINE-SHOOT MOTH. 7 repeated infestation of the leading twigs during several consecutive seasons producing additional malformations which result in a much distorted tree of little commercial value. If the pest becomes more abundant, then the trees are transformed by the effect of the injury into unsightly crippled bushes with no commercial value. DESCRIPTION. THE ADULT. (PI. II, upper figure.) The European pine-shoot moth is a small, gayly colored moth, about one-half inch long and measuring about three-fourths of an inch across with the wings extended. The head and its appendages and the thorax are light orange-yellow, and the abdomen is dark gray. The forewings are bright ferruginous orange, suffused with dark red, especially tow^ard the tips, and with several irregular, forked anastomizing, silvery crosslines and costal strigulse; the hindwings are dark blackish brown. The legs are whitish, the anterior ones reddish in front. THE EGG. The egg is very small, flat, whitish in color, and is laid singly at the base of a bud. Dissection of a female abdomen proves that upwards of a hundred eggs are laid by each female ; this is a rather greater fecundity than is normal in this group of insects. THE LARVA. (PI. II, lower figure.) The young larva is dark brown with deep black head and thoracic shield, the latter divided by a narrow central line. The body of the older larva becomes somewhat lighter, but is still much darker than the larva of any of our allied native species. The full-grown larva is two-thirds of an inch long. THE PUPA. The pupa is stout, robust, light chestnut brown with darker head and back. The wing covers reach to the end of the fourth abdominal segment. The abdominal segments are armed with rings of short, sharp, blackish-brown spines. ALLIED AMERICAN SPECIES. There are in this country several indigenous species closely allied to Evetria huollana^ and like it confined to pine. ' Some of these already constitute a serious problem and periodically do considerable 8 BULLETIN 170, U. S. DEPARTMENT OF AGRICULTUEE. damage to pine forests and more often to pine nurseries. They are the more capable of injury because there are two generations an- nually and they thus have two chances each year to accomplish their damaging work. None of these native species can, however, even with this advantage, be compared in destructiveness to the European species just introduced. This is partly due to the larger size of the introduced species and to the greater voracity of the larva, but is mainly due to the difference in the attack, which causes a different reaction of the tree. The larva of the native species of the genus confines itself to a single twig and finds its food within this or within a single bud, or at most a few buds. This bud or twig dies, but the tree responds with the natural groAvth of the next set of buds and very often recovers from the injury without permanent disfigurement. The resulting injury to the trees is serious only when these native species are present in unusually large numbers. Moreover, each of the native American species is more or less confined to a single or a few species of Pinus, but the European i:)ine-moth thrives indiscriminately on all species of Pinus and has consequently a greater chance to become excessively abundant. While several of the native species are continually of some economic importance and periodically become a serious menace even to larger trees, it is mainly when they occur in large numbers in nurseries that they become really troublesome. Large trees become checked in their growth by the loss of terminal twigs, but are not necessarily seriousl.y deformed in their future growth, although an undesirable forking of the tree to^^ is a quite common result. On the other hand, the larva of the European pine-shoot moth is very voracious and not only destroj^s a number of buds and young sprouting shoots by eating their interior, but it invariably damages the remaining shoots in the cluster bj'^ nibbling their bases on the inner side. The subsequent growth of these injured shoots, in the effort to supplant the destroyed leader, causes greater permanent injury to the value of the tree than if they were entirely removed. NATURAL ENEMIES. Evetria huoliana in Europe is, to some extent, kept in check by a large number of parasitic enemies. As early as 1838 Hartig^ recorded 14 ichneumonid wasps and 1 tachinid fly - which he had reared from pupa? of the pine-shoot moth. It has since been ascer- tained that there are several other parasites ; among the ichneumonids Katzeburg considered the following three, which he himself had reared, as the more important: Prlstomerus vulnerator lr*anz., Cre- mastus interruptor Grav., and Orgilus ohscurator Hald. 1 See " Literature," p. 10. - Actia pinipcnnis Fallen. THE EUROPEAN PINE-SHOOT MOTH. 9 To promote the good work of these parasites specially constructed rearing houses have been erected in Europe diu-ing bad outbreaks of the pine moth. The infested twigs are collected in these small houses, which permit the escape of the parasites but not of the moths. It is reasonable to suppose that some of the native parasites on some of the native species of Evetria will in time also attack Evetria huoJiana in this country — in fact, parasitized larvae have already been observed — but these native parasites can not be relied upon to keep in check their natural hosts, the American pine moths, which sporadically become very abundant and injurious in spite of the parasites, and presumably will be less effective in controlling the newly introduced host. METHOD OF CONTROL. The larva of the European pine-moth is so effectively protected within the buds that it can not be reached b}'^ any insecticide, and the onl}' method of combating it is that used in Europe for more than a hundred years, namely, the pruning and destruction of the in- fested buds and twigs together with the larvae they contain. Such hand picking is practiced every year in the government-controlled forest reserves of Europe. This pruning must be done while the insect is within the twigs, and while it may be done throughout the entire year, except during the midsummer months when the insect is in the adult stage, it can be most profitably done in the fall and winter months while the young larvae are yet within the undeveloped buds, because the prun- ing at this time will enable the secondary set of buds to develop in the spring without delay. The only drawback to the collecting of the larvae in the fall and winter is that the infested buds are then less noticeable than in the spring when the injury is further devel- oped. A little practice, however, soon enables instant recognition of the infested buds, even by an unskilled laborer ; the slight exuda- tion of pitch at the base of the bud covering the entrance hole of the larva (PL III) is very characteristic and easily recognized when once known. In the spring, when the buds develop into young shoots, the in- jury is very much more apparent, and anybody can then distinguish the infested twigs at a glance. For this reason it is advisable to have the trees gone over again in the spring, so as to remove any infesta- tion which has been overlooked in the fall. In America the work of the larva in the fall (September, October, and Xovember) has pro- gressed far more and is much more easily discovered than is the case in Europe, where the larvae have attained very small proportions and 10 BULLETIISr 170, U. S. DEPARTMENT OF AGEICULTUEE. have attacked only one or two buds before the winter resting period intervenes. The fact that this species is stationary during the greater part of the year and only found within definite parts of certain kinds of trees, namely, in the next 3^ear's buds of pines, makes effective con- trol work much easier than is the case with insect pests which are general feeders and which are not confined to definite parts of the food plant, as, for example, the gipsy moth or the brown- tail moth, '^'^liile the European pine-shoot moth is confined to nurseries and private parks and has not spread to the native pines, it should prove a comparatively easy task to eradicate the species absolutely within any limited area. At the present time it would even seem possible completely to stamp out this dangerous pest in America, and forestall the infestation of our native pine forests, provided that the danger of new infestation is removed. But when once the species has multiplied sufficiently to become generally dis- tributed on the native pines the possibility of eradication will be past. SYNONYMY OF EVETRIA BUOLIANA SCHIFFERMILLER. Tortrix huoliana Scliiffermiller, Syst. Verz. d. Sclimett., p. 128, 1776. Coccyx huoliana Treitscbke, Schinetterlinge von Europa. vol. 8, p. 140, 1830. Tortrix {Coccyx) buoUana Ratzebnrg, Die Forst-Insecten, vol. 2, p. 202, 1840. Retinia huoliana Guenee, Europaeornm Microlepidopterorum index methodicus, p. 46, 1845. Coccyx huoliana Herrich-SchJiffer. Bearb. d. Schmetterlinge von Europa, vol. 4, p. 221, 1840. Evetria huoliana Meyrick, Handbook of British Lepidoptera, p. 470, 1S95. Evefria huoliana Rebel, Catalog der Lepidoptereu des palaearctischen Fauneu- gebietes, T. II, No. 1851, 1901. LITERATURE.^ 1776. Scbiffermiller, I. Systematiscbes Yerzeicbniss der Scbmetterlinge der Wiener Gegend. Wien. Original description of Evetria 'buoliana. 1809. Niemann, E. Forststastistik der Danischeu Staateu, Altoua. Describes outbreak in Denmark in 1805-1807, and the collecting of larva? in the effort to control the species. 1838. Hartig, T. Tortrix huoliana. In Jahresbericbte liber die Fortschritte der Forstwissenscbaft und forstlicben Naturkunde, Jabrg. 1, Heft 2, . p. 267-268, Berlin. Records the rearing of 15 species of parasites from Evetria huoliana. 1840. Ratzebnrg, J. T. C. Die Forst-Insecten, T. 2, p. 202-207, Taf. XIV, fig. 4. Berlin. Detailed account with illustrations of the life history, work, economic im- portance, remedies, natural enemies, and literatui'e of the species, with notes of severe outbreaks in Germany, 1835-1838. 1 This is not intended to be a complete bibliograi^y of Evetria huoliana; a large num- ber of special articles have appeared in various publications in Europe, and every hand- book on insects or forestry contains more or less exhaustive accounts of this pest. THE EUROPEAN PINE-SHOOT MOTH. 11 1895. Judeicb, J. F., and Nitsche, H. Lelirbuch der mitteleuropaischen Forst- insektenkunde, Bd. 2, p. 1004-1008. Wien. Condensed (5 pages), life-history and economic importance with original figure of the injury done by the species. 1897. Lovink, H. J., dud Eitzema Bos, J. Schade in jonge deunen bosschen teweeg gebracht door rupseu uit bet bladrollergeslacbt Retiiiia Gn. (" dennenknoprups " " dennenlotrups " " harsbuilrups " ) . /;i Ti.idschr. Plantenziekten, Jabrg. 3, Afl. 4, p. 83-133, figs. 6, pis. V-VII, Oct. Detailed account of the species and its injury, with colored plates. 1897. Severin, G. Insectes. Extrait du Catalogue d6tallle et lllustre du Pa- vilion des eaux et forets a I'Exposition internationale de Bruxelles- Tervueren, p. 46-49, pi. X. Bruxelles. Contains short illustrated account of Tortrix (Retinia) buoliana Schjflfer- miller and its injury : Plate I of the present paper has been copied trom this article. 1898. Boas, J. E. V. Dansk Forstzoologi. Copenbageu. Condensed life history, injury, and references, with original observations and figures. 1898. Hess, R. A. Der Forstscbutz, ed. 3 enl., v. 1, p. 492 494, figs. 174-175. Leipzig. Condensed handbook information on Tortrix (Retinia) huoUana Schiff. 1901. Severin, G. Le genre Retinia, Pyrale des pommes, des bourgeons, de la resine. In Bui. Soc. Cent. Forest. Belg., t. 8. p. 598-605. 674-685. 2 pis., 7 figs. Monographic account of the three most important injurious species of the genus Evetria in Europe, with text figure and colored plate of Evetria buoliana. It should be noted that the larva figured under and credited to Evetria buoliana belongs to Evetria resinella, figured on the next colored plate, and vice versa. 1912. Gillanders, A. D. Forest Entomology, ed. 2. Edinburgb and London. Condensed handbook information. 1913. Niisslin, O. Leitfaden der Forstinsektenkunde, 2. neubearb. und verm. Aufl., p. 417^18. figs. 350, 352. Berlin. Condensed handbook information on araphoUtha (Evetria) buoliana Schiff. 1914. Busck, August. A destructive pine-moth introduced from Europe {Eve- tria buoliana Scbiffermiller). In Jour. Econ. Ent., v. 7, no. 4. p. 340- 341, pi. IX, August. First notice of the pest in America. ADDITIONAL COPIES OF THIS PUBLICATION MAT BE PEOCtTEED FROM THE SUPERINTENDENT OF DOCUMENTS GOVERNMENT PRINTING OFFICE WASHINGTON, D. C. AT 5 CENTS PER COPY WASHINGTON : GOVERNMENT PRINTING OFFICB : 1915 UNITED STATES DEPARTMENT OF AGRICULTURE DEPARTMENT BULLETIN No. 1490 Washington, D. C. July, 1927 DEFECTS IN TIMBER CAUSED BY INSECTS By Thomas E. Snyder, Entomologist, Forest Insect Investigatians, Bureau of Entomology CONTENTS Page Introduction 1 Types of insect defects ; definitions- 4 Pinlioles 6 Grub holes G Powder post 7 Defects classed as pinholes 7 I'inhole defects formed in living trees ; a nonpreventable loss- 10 Pinholes in living trees caused by ambrosia beetles- 10 Pinholes in living trees caused by timber worms- 14 Pinhole defects formed in wood after the trees are felled ; a preventable loss 15 Pinholes in felled trees caused by ambrosia beetles. 15 Pinholes in felled trees caused by timber worms- 16 Pinhole injury to imported logs- 22 Defects classed as grub holes or wormholes 23 Grub-hole injury to living trees ; a nonpreventable loss 25 Grub-hole injury to green sav/ logs and lumber ; a prevent- able loss 26 Defects classed as powder post 27 I'owder post caused by Lyctus beetles 28 Page Defects classed as powder post — Con. Powder post caused by Ptinidae and Anobiidae 32 Powder post caused by Bostrich- idae 32 Powder post caused by round- headed borers (Cerambycidae)- 33 Powder post caused by flat- headed borers ( Buprestidae) 34 Other types of defects 36 Defects classed as ring distor- tions 36 Ring distortions caused by defoliation by the bud worm 36 Defects classed as pitch pockets and pitchy timber 37 Defects classed as gum spots or streaks 38 Defects classed as black check- 39 Defects classed as bluing or staining 40 Defects classed as pith flecks 43 Pith-fleck injury caused by the larvae of flies 43 Pith-fleck Injury caused by the feeding of adult wee- vils 43 Summary 43 Literature cited 44 INTRODUCTION It is extremely difficult to estimate the losses due to defects in timber caused by insects. Where the grade of lumber is lowered, the loss may be ascertained by the reduction in the grade, because of the number or size of the holes caused by insects. However, where entire large oak or spruce trees are left to rot in the forest, 38252°— 27 1 1 2 BULLETIN 14C0, U. S. DEPARTMENT OF AGRICULTURE because the wood has pinholes in it and hence is not suitable for high-grade cooperage or airplane stock, the loss is greater, but per- haps more intangible. Where such timber is accessible and there are suitable markets, it need not be an entire loss, but could be used for lower-grade products. Closer utilization is of prime impor- tance in the j)revention of waste in the conservation of our forest resources. Better methods of manufacture and the use of forest products, and the elimination of waste, as advocated by the Federal Forest Products Laboratory at Madison, Wis., and the Bureau of Stand- ards of the Department of Commerce, will go far in helping to relieve the great timber shortage, which is especially serious in the case of the hardwoods. The purpose of this bulletin is briefly to describe and illustrate, from the viewpoint of the entomologist, for the benefit of graders, inspectors, manufacturers, or utilizers of timber products, the prin- cipal types of defects in timber caused by insects, the causes of these defects, and, where possible, the mode of applying recommended methods to prevent the damage and loss. The Forest Service has already published a circular on grading lumber (SO).^ Wood-boring insects not only destroy a considerable quantity of forest products, but also cause the loss of the labor expended during the process of their manufacture. The trees from which these prod- ucts were cut are a loss, and additional trees must be taken from the forest to replace them. To this loss must be added percentages of the cost and upkeep of lumber camps, machinery, equipment, logging railroads, wages and keep of men and animals in the woods, storage in the mill pond, sawing, drying, finishing, and piling at the mill. The direct money loss caused by insects to cut timber and lumber assumes an enormous aggregate — greater proportionately than that caused by insects to living timber. To the money loss of production costs must be added the loss of time necessary to properly season the wood. Of course, damage to seasoned finished wood products causes relatively greater loss than does damage to crude forest products. Where the products are damaged after being put in place, the cost of replacement involves additional loss of labor and time, as well as the cost of the original and replaced products, a loss far greater than the value of the raw products. Often such replacement charges should be charged to both wood-destroying fungi and wood-boring insects and not to one agency alone, as frequently there is a close relationship between these forms of life in the destruction of timber. However, in many cases wood-destroying fungi alone are responsible for the destruction. It has been demonstrated in practice that a large percentage of the $45,000,000 annual loss (4-7 ) caused by wood-boring insects in the past can be prevented in the future. The increased prices of lumber and all other forest products make it even more essential that all avoidable waste caused by insect defects should be eliminated in the interest of conservation. 1 Reference is made by italic numbers in parentheses to " Literature cited," page 44. DEFECTS IN TIMBER CAUSED BY INSECTS In order to accomplish this saving it is necessary for manufac- turers of wood products to utilize all available information that has been obtained from experiments carried on for many years by the Bureau of Ento- mology, especially the results of scientific re- search on the specific causes of the differ- ent types of insect defects and methods of 25i"6 venting them. Data contained in earlier bulletins by exj^erts of this bu- reau, as Avell as new and unpublished data, have been used freely in this bulletin. The published articles by Hopkins {2J, '24, 25, 26, 27, 28, 29, 30, 3U 32, 33, 34, 35), Burke (^,7), Webb {50,51), Craighead {9, 10, 11, 12, 13, 14), Snyder and '^), 44-) 4^') 4^ St. George (^7) were the source of much information. The pioneer investi- gations and publica- tions of Doctor Hop- kins, former forest entomologist of the Department of Agri- culture, in reality form the basis for this bulletin. Doctor Hopkins's investiga- tions have done much to prevent waste and losses due to insects. References to these and many other pub- lications are to be found in Chamber- lin {H). Timber inspectors and graders should be able to determine from the caused by insects workine; Fi(i. 1. — Black lioli's in wliiii- cohiiiihianus. A, slightly lUlar; ml; i;i,wi.' liv Cortln/his ■d ; D, sliglaily reduced defect in the wood whether it was in (1) the living tree; (2) the freshly felled, green saw log or bolt, with or without the bark on; (3) the green, unseasoned lumber ; or (4) seasoned rough or finished product. BULLETIN 1490, U. S. DEPARTMENT OF AGRICULTUEE The rejection of timber with insect defects caused in the tree, log, or green lumber before the wood is dry or seasoned is often an avoidable loss, because the insects are no longer working in the wood. This type of insect defect is analogous to " pecky^ cypress " caused by a fungus. Even though the defects are such that they materially affect the strength of the wood or otherwise unfit it for the special use intended, there are still many purposes for which it can be used. The grade may be merely lowered, according to the number and size of the holes; or the defect may unfit the wood for special uses, owing to unsightly appear- ance, likelihood to cause leaks (as for barrel staves and heads for tight cooperage), or weak- ening (as for high-grade air- plane stock). Much waste can be avoided by utilizing such defective timber for other uses and in lower grades than origi- nally intended. Damaged implement or ve- liicle stock and other material in which great structural strength is required can be used for less exacting purposes, the defect being plugged and painted over; while low-grade lumber with wormholes but no living worms or decay can be used as the base for veneer if the holes are not large enough to cause depressions in the face veneer. On the other hand, the acceptance of material infested by powder-post beetles may lead to serious results through a break at a critical moment. Special reference is made in this bulletin to the protection and conservation of both crude and finished wood products, such as lumber, bolts, cooperage stock (finished and unfinished), agricultural- implement handles, tent poles, vehicle parts, timber for shipbuilding, oars, airplane stock, and other high-grade products. TYPES OF INSECT DEFECTS; DEFINITIONS The principal types of defects caused by insects may be classed in three definite groups, namely, pinholes, grub holes, and powder post. (Table 1.) The terms for these defects are those generally used by the loggers in the woods and the sawyers and graders at the mill. Fig. 2. — " Calico poplar," a defect caused by an ambrosia beetle (Corthylus columbi- anus). (^5) DEFECTS IN TIMBER CAUSED BY INSECTS t4 u 1^ o o d m i oi s 6i i _ l' r/,' . o >.S o o o ;^o 6 6 Ph I? 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DEPARTMENT OF AGRICULTURE PINHOLES Pinholes are small, round, usually open holes ranging from one one-hundredth to one-fourth of an inch in diameter ; they are made either by ambrosia beetles or timber Avorms. Pinholes caused by ambrosia beetles are of two types: (1) Pinholes caused by adult beetles boring into the trunks of growing trees for the purpose of laying eggs and rearing their young, or by larvae, which also may burrow in the wood; (2) pinholes made by adult beetles or larvae in freshly felled green saw logs (with or without the bark on), bolts, and green or partly seasoned lumber. In commercial grading rules for various species of timber pin- holes constitute a standard defect (considering only w^ormholes), but are sometimes recognized as "equivalent defects," that is, equivalent Fig. 3. -Work of ambrosia beetles in both sapwood and hrartwooU nf southoru yeUow pine to other defects, such as knots. This grade in certain hardwoods is termed " sound wormy " and is of that class of defects in timber or lumber in Avhich the insects are no longer present and hence no fur- ther damage results to the timber. GRUB HOLES Grub holes or the larger wormholes are oval, circular, or irregular holes three-eighths of an inch to 1 inch in diameter, produced by adult insects (1) boring into or laying eggs in the trunks of living trees, or (2) boring into green, recently felled logs for the purpose of laying eggs or rearing their young; the young or larvae cause most of the injury to the wood, Avhich serves as both food and shelter. Grub holes may also be classified as standard defects. DEFECTS IX TIMBER CAUSED BY INSECTS Fig. -Pinholes caused by the pine-wood staincr (Gnathotiichus materiarius) POWDER POST Powder post is that class of defects in which the larvae of insects reduce the Avood fibers of seasoned or partially seasoned wood to a powderlike condition by boring through the wood, which is both their shelter and their food. Powder post occurs only in the seasoned or partially seasoned sap- wood or heartwood of both hardwoods and softwoods. Logs, bolts, timbers, lumber, and crude or finished prod- ucts are attacked. The infested wood is al- ways more or less filled with fine or coarse powdery or granulated laoring dust and is called powder-posted. This tjY'Q' of injury is dangerous, since the grubs continue their destructive work in the wood and also infest other timber near by. DEFECTS CLASSED AS PINHOLES The term " pinholes " undoubtedly origi- nated w^ith stave mak- ers and coopers, from the fact that such holes are often plugged with small wooden pins. Pinholes are small, round holes one one- hundredth to one- fourth of an inch in diameter in both the heartwood and sap- wood of hard (broad- leafed) and soft (co- niferous) living trees, green, moist saw logs, bolts, green timbers, or green piled lumber. These holes are made 1 -.I 1 • B^iG. 5. — Pinholes in sapwood Dou; by either ambrosia xyioterua sp. jlas fir made by 8 BULLETIN 1490, U. S. DP:PARTMENT OF AGRICULTURE beetles or timber worms. In tbe former case (where caused by am- brosia beetles) the holes are made by both the small, slender, cylin- drical, adult beetles, and, after hatching within the wood, by their ■>j..'«h'»''"'»*').1|'|,Sb Fici. G. — Pinholes made by the spruee timber beetle (Xylutcrus blvittatus) in red ypruee, West Virginia larvae or young. In the latter case the injury is caused entirely by the larvae or grubs (young) of beetles or the so-called timber worms. DEFECTS IN TIMBER CAUSED BY INSECTS 9 The larvae of some types of ambrosia beetles excavate side gal- leries at right angles to the gallery made by the adult, which tun- nels into the wood to deposit eggs; other types excavate no side galleries. Some holes are clear; others are stained black by the action of fungi, some of which the beetles cultivate for food in their Fig. 7. — Pinholes caused by ambrosia beetles in heading and tight cooperage in South Carolina ■Xy'.ifij' :3 X^ Fig. S. — Pinholes in grct^u bie-kor.v lumbur cuubcd L.v au umbr-^ia beetlo (A'lilc- hoi us xyloyraphuH) galleries. Injury to green heartwood stock and to partly seasoned stock of such woods as hickory and cypress in many cases does not produce the stain. These holes are always open (never filled with dust), and are either clear or black and associated with discolored streaks or stains 38252°— 27 2 10 BULLETIN 1490, U. S. DEPARTMENT OF AGRICULTURE in the suiroimdin■ \iihliiinis sp. in green chestnut board, after piling ' Corthylus columbianus Hopkins. 12 BULLETIN 1490, U. S. DEPARTMENT OF AGRICULTURE Fig. 11. — Pinholes in the sapwood of high-grade cypress blocks ; end view of logs in freight car ; wood completely riddled by ambrosia beetles (Platifpiis compositus and Xylchorus sp.) Jiiiii{;!;Ai '!l m\}' ill' il w -.uiiS Iff! >i II 1 1 11 I II ii t fi H ' >';'! \ '. Fig. 1-. — i'iiiholL.^ caused by ambrosia beetles (Xyleborus sp.) iu mahogany Hitches DEFECTS IN TIMBER CAUSED BY INSECTS 13 A loss of $5 to $20 per thousand feet of timber is a conservative esti- mate. This defect is classed as " wormholes, no living worms or de- cay," and can not be pre- vented in the tree, but of course similar defects in the green stock can be prevented by proper handling. Pinholes one twenty- fifth to one-eighth of an inch in diameter in both heartwood and sapwoocl of hardwoods and soft- woods (figs. 1, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, and 14) are caused by similar beetles.^ The defects caused by these pinholes and stains (discolored streaks and joatches) (figs. 1, 2, 3, 4, 6, 9, and 13) reduce the grade of timber and its full strength, unfitting it for structural timber, wagons, agricultural implements, tight cooper- age, and shingles. A 25 per cent loss of elm cooperage stock in logs at the mills in Illinois was due to such defects. In some cases millions of feet of timber have been reduced 10 to 25 per cent or more in value by pinhole de- fects. In deadened standing cypress in the Gulf States, pin- hole injury can be prevented by gir- dling the trees in Alarch, April, Oc- tober, and Novem- ber 1^8), but from August to Septem- ber is apparently the most elfective season. Fig. 13. — Pinholes caussi'd by ambrosia beetles (Xi/le- borus sp. ) iu imported greenheart (Xcctaiulra rodioei) Fig. 14. — Pinhole daniage by ambrosia ...n.i.-, yXylfhwic-i gretiadensis) to Huia wood (Rakuda) imported from Cen- tral America " Platypus, Monarthrum, Xyleborus. 14 BULLETIN 1490, U. S. DEPARTMENT OF AGRICULTURE PINHOLES IN LIVING TREES CAUSED BY TIMBER WORMS Pinholes or wormholes in the heartwood of chestnut and red oak, one one-hundredth to one-fourth of an inch in diameter, open, clear, not stained, but lined with a substance about the color of the wood, a large number of holes in a given space, are made by timber worms hatching from eggs laid in or near scars. The holes made by the grubs are not of uniform size; they may extend several feet through the wood. (Fig. 15.) This defect, due to the chestnut timber worm,* is one of the most common and serious defects in chestnut timber throughout its range. It is rare to find chestnut trees, logs, or telephone or telegraph poles free from this defect, and practically every tree of merchantable size is more or less affected. There is a very low percentage of " clear " chestnut, the re- mainder being " wormy " and reduced to the lower grades. This defect is a " sound wormy " injury and can not be pre- vented. Unfortunately the chest- nut is rapidly becoming extinct as a commercial tree, owing to the chestnut blight fungus. "VVormy chestnut and oak wood can be used wherever structural strength is not necessary. They are especially suitable as the base for veneer in manufactur- ing pianos, caskets, coffins, auto- mobile running boards, and the lower grades of building lum- ber, because of the comparatively reasonable price at which this grade of lumber can be bought. Much timber that would other- wise be wasted can be thus uti- lized. There is, however, a limit to the size of the holes ad- mitted. Similar jDinholes or wormholes one one-hundredth to one-eighth of an inch in diameter in oak timber (fig. 16) are caused by the oak timber worm.^ This defect is especially serious in large mature white oak trees. The holes occur in large numbers in a given space and extend in all directions through the solid heartwood. This insect usually affects the wood of the finest old, mature, or over- mature trees, sometimes causing defects which result in the discard- ing of entire trees for such uses as tight barrel staves. This defect is classified under the term " wormholes, no living worms or decay," and can not be prevented when occurring in living trees, although losses can be lessened by clean forest management; that is, removal •flm Fig. 15. — Holps c.iused by the chestnut timber worm (Mclittomma sericeum) , vvliich cause.s the defect classed in the grade " sound wormy chestnut " * Melittomma sericeum Harris. ^ Eupsalis minuta Drury. DEFECTS IN TIMBER CAUSED BY INSECTS 15 of old dead and dying snaiw,W'* m.Ki.i^ni {m ;if1 Fig. 22. — Grub holes madf by the oak carpenter worm (Prionoxystus robiniac) seasoning of green freshly sawn timber or lumber by open or loose piling is a preventive. In cribbing or proper piling of green sawn stock to facilitate rapid drying, care should be taken to insure against severe checking from too-rapid drying. Heavy dimension timber should be stacked in loose piles. If it were possible to kiln-dry the material,, insect damage, of course, would be prevented. In the case of damage to stave stock, by special methods of sawing the waste can be reduced to a minimum and a very considerable saving of material effected. Where the holes are not too numerous, they can be plugged with wooden pins and the wood used for casks. DEFECTS IN TIMBER CAUSED BY INSECTS 21 Fig L'3.— a, grub holes in overcup oak. uuide by the Parandra borer {Parandia brunnea) near Vicksburg, Miss. ; B, grub holes in soft maple made by the 1 arandra borer in Maryland 22 BULLETIN 1490, U. S. DEPAETMENT OF AGRICULTURE The defect does not deteriorate furniture and inside-finish stock. This defect is considered under " wormholes, no living worms or decay," and in the interest of conservation and closer utilization, timber with these defects should be used. Fig. 24. — A, grub holes made by ; pitchy " fatwood " of the basal lo; tree PINHOLE INJURY TO IMPORTED LOGS flat-headed borer (Buprestis aprioanfi) in the of long-leaf pine ; B, the same in a turpentined Large quantities of tropical woods in the rough, round, or squared log are 3'early shipped into the United States from Central and South America, the West Indies, Africa, and the Philippines. (Figs. 12, 13, and 14.) Almost invariably such timber, if received within a 3'ear after it is cut, contains many species of pinhole-boring beetles, .but these never live over the winter, except perhaps in the Gulf States. DEFECTS IN TIMBER CAUSED BY INSECTS 23 Under present methods of lumbering, such imported logs usually are infested by pinhole-boring beetles of many species, which attack the logs after they are cut, and continue to live in them for several months and in some cases a year or more. If such logs are shipped into another country with a similar climate, the insects may survive and attack logs of native timber; if, on the other hand, logs are exported to a much colder or hotter country, the insects will rarely, if ever, become established in the country of import. There is, therefore, some danger of introducing destructive species through the commercial interchange of timber in the form of lo"-s. Fig. 2."). — Wormholes caused by " sawyers '" (J/ onoc/i«»n/.v spp.)iii pine. A and B, woimholes in southern yellow pine ; C, wornUioles in white pine For example, many ineect species are widely distributed over tropical America that do not occur in tropical Africa, Asia, Australasia, and the Pacific islands. Tropical Australia, the Philippine Islands, and tropical Japan doubtless have a . considerable number of the same species of pinhole borers. One country may have a few that do not occur in the others. DEFECTS CLASSED AS GRUB HOLES OR WORMHOLES Grub holes are medium to large, circular, oval, or irregular holes from three-eighths to 1 inch in diameter, in both sapwood and heart- 24 BULLETIN UCO, U. S. DEPAKTMEXT OF AGRICULTURE wood of all kinds of timber. They may either be stained black inside or be of the same color as the surrounding -wood, and they may be free and open or filled with tightly-lodfred boring dust, depending on the kind of insect making them. This boring dust does not fall out when the wood is jarred. Grub holes are made in the living tree, in the saw log, or in piled green lumber. In nearly all cases the injury is caused by the 3'oung borers, sawyers, or grubs, but occasionally also by adult termites or white ants (fig. 18), adult Fig. lil). — Woimhole dufucts in codar, caused by the rouiul-hoaded borer VuUidium aiiteniiatuin carpenter bees ^^ (fig. 19), or carpenter ants^^ (fig. 20), or by the larvae of horntails ^^ (fig. 21). Usually this type of injury is con- sidered as " wormholes, no living worm's or decay," especially if the holes are stained black, and no further damage will result, except in rare cases. Grub holes constitute a standard defect and are also included under "equivalent defects." They are often of considerable size ^^ Xi/locopa spp. " Caiiipoiiotiis spp. 1" Tnmcv oolnmba 1... or i^irea- spp. ; they usually damage only dead wood or trees or logs that have been left in the woods too long. DEFECTS IN TIMBER CAUSED BY INSECTS 25 and consequently reduce the structural strength of the wood, espe- cially when cut into smaller dimensions; therefore timber having such borer holes should be used in as large dimensions as possible. Fig 27. — Western red cedar shingles badly damaged by grub holes and burrows of flat-headed borers {Trachykcle hlondcli) . (.). a, Quarter- sawn shingle showing both cross and longitudinal sections, c, d, ot tue larval mines ; b, bastard-sawn shingle showing larval mines GRUB-HOLE INJURY TO LIVING TREES; A NONPREVENTABLE LOSS Grub-hole defects in living trees can not be prevented by lumber- men, since often these defects occurred many years before tlie tree was cut. Sometimes the insect holes are partially healed over by 26 BULLETIN 1400, U. S. DEPAETMENT OF AGRICULTURE new growth of the tree, or they may have been enlarged by carpenter ants. This type of injury can be recognized as follows: (1) In the sap wood and heart wood of hardwoods very large cir- cular holes, one-half to 1 inch in diameter, are open and but slightly stained and are usually lined with a silky yellowish-brown web.^" (Fig. 22.) (2) In sapwood or heartwood of hardwood trees the holes are darkly stained and are open, containing little or no sawdust or f rass.^^ (3) In the heart- wood of butt logs of gum and a few other hardwoods, unstained holes contain mined granular and fibrous frass^s (fig. 23). (4) In the heart- wood of . butt logs of softwoods, chiefly pine, very irregular holes are narrowly oval, without stain, but surrounded by much pitchy " light- wood," or " f atwood," and are very tightly packed with f)ne granular frass ^^ (fig. 24) {?■). (5) Pinholes or w o r m h o 1 e s in soft- Avood logs and lum- ber in the Northern States are caused by a melandryid timber worm.-'' These larvae gain entrance to the living sapwood through scars or blazes and also attack recently felled timber. The holes are filled with fine sawdust. GRUB-HOLE INJURY TO GREEN SAW LOGS AND LUMBER; A PREVENTABLE LOSS All types of borer holes other than those mentioned above are made after the trees have been felled, and are preventable by proper methods of handling the logs. These borer holes occur in the sap- FiG. 28. — Powdpr-posted white ash shipbuilding lumber showing larval burrows and exit lioles of adults of Liictus planicoUis : board from a closely piled stack of lumber throughout which larvae had burrowed ^^ This injury is found principally in oak, chestnut, locust, and cherry and is caused by the carpenter worm, J'noiioj'ttstiis robiniae Peck. " These holes are found principally in oaks and are caused by the round-headed borers (Cerambycidae) (Joes S|]p. and Jiomaleum sp. ; in hickory, they are caused by Goes sp. ; in hickory in the South, small darkly stained holes are caused by a wood-boring cater- pillar, Cossula masjniflca Bailey ; and in hard maple they are caused by the maple-tree borer, Olycohlus speciosus Say. ^^ This iniury is caused by Parandra trunnea Fab. 19 This injury is caused by Buprestis apricann llbst. and occurs especially in fire- scarred long-leaf pines and trees boxed for turpentine. This borer causes an excess of pitchy wood near the injury. The injury often amounts to the reduction of 5 to 10 per cent "of the lumber to lower grades and the wind-throw of much second growth on turpentine operations. '" Sen-opalpits harbatus Schall. DEFECTS IN TIMBER CAUSED BY INSECTS 27 wood of hardwoods or softwoods as unstained irregular holes from one-fourth to 1 inch in diameter, which may be open, loosely or tightly filled with powder, with granular or fibrous frass, or with pellets.-^ These and similar types of borer injury can be prevented by prompt handling of the logs after they are felled. I-iogs, bolts, and sawn or squared timbers should never be allowed to lie wiiere cut in the woods, after the of 1st of February in the Gulf States, or after the 1st of April farther north. Other preventiA'e measures include : Rapid utiliza- tion; submergence of logs in water, where they will not be at- tacked, and working them up as soon as re- moved from the water ; sun-curing, with or without the bark on (care should be taken to provide against ex- cessive checking) ; and removal of bark strips from freshly sawn ma- terial. The damage can often be prevented by peeling the bark (both outer and inner) from the logs or bolts, timbers, or edges of lumber, as the bark offers a favorable place under which the in- eggs. and Fig. 29. — Puwder-posted sapwoud oak wni'er laid on a core of chestinit (door stock) ; work of Lyctw^ pUnii- coUis. Note that the heartwood oak and the chestnut have not been attacked sects can lay Both the outer inner bark of sawn timber should always be carefully removed and the timbers placed where they will season rapidly (i). DEFECTS CLASSED AS POWDER POST Powder post is indicated by holes from one-sixteenth to one-fourth of an inch in diameter, in the surface of the wood, in the sapwood and =iThe principal injury of this character found in pines, spruces, and flrs is caused by the pine sawyers, Munochamits spp. (fig. 25) (50) ; the loss due to pine sawyers in green logs and storm-felled timber is often as high as 35 per cent. In ash the defects .nre caused bv the banded and red-headed ash borers, Neoclylus capraea Say and erythroccpha- liis Fabricius; in hickory bv the banded hickoiy borer, OyUeiu' pU-tux Drury, and the red-headed ash borer; in locust by the locust borer, Cyllene robintae Forster : in cedar by the round-headed borer CaUidium initc una turn Xewm. (fis. 2(i) ; in cypress, western redwoods, and cedars bv flat-beaded borers, Trachijk-ele spp. Burrows made liy Trnchykele are tightly packed with pellets of excrement, and shingle stock is full of holes (hg. 27) (7). 28 BULLETIN 1490, U. S. DEPARTMENT OF AGRICULTURE heartwood of both hardwoods and softwoods, from which the powder will fall when moved or jarred.^^ The interior is honeycombed by irregular burrows made by the larvae and when badly damaged is converted into a mass of closely packed material, which readily crumbles into' fine fiourlike powder or coarser pellets of excreted wood. This is held together by an outer thin shell and intervening fibers of sound wood. These defects will be discussed in the order of the size of the holes caused by the various types of insects. All powder-post damage can be prevented. POWDER POST CAUSED BY LYCTUS BEETLES The injury caused by Lyctus beetles is confined to the white- wood or sapwood of hardwoods (-M). It consists of small holes one-sixteenth to one- twelfth of an inch in diameter, with irregu- lar burrows filled with flourlike powder. Air- dry or kiln-dry sap- wood material, and sapwood which has been stored or piled in one place for two, three, or more years, especially second- growth ash, hickory, and oak, are princi- pally affected; but other hardwoods, such as walnut, maple, jiersim- mon, cherr}", elm, poplar, and sycamore, are also damaged. Seasoned shipbuilding and airplane lumber and gunstock blanks, stored in large quantities, and finished stores, such as wheelbarrows, tent poles, oars, airplane parts, shovel and pick handles, and many other hardwood articles used in the military services are subject to serious damage by powder-post beetles. (Fig. 28.) Hickory, ash, and oak furniture, interior woodwork of buildings (fig. 29), and the woodwork of farming machinery and implement handles; ladder stock, such as rungs; vehicle stock, such as hubs, spokes, felloes, rims, singletrees, poles, and shafts; and cooperage stock (barrel-stave bolts) are also injured. Fiu. JO. — I'owdur-post defect in pine uiadi.' by Xyhthius peltaUts -- Insects which have this peculiar habit of reducing wood fiber to a powderlike con- dition belong chiefly to the families Lyctidae, I'tinidae, Anobiidae, Bostrichidae. and Cerambycidae. By far the larger part of the injury is caused bj- species of the genera Lyctus and Neoclytus. DEFECTS IX TIMBER CAUSED BY INSECTS 29 The loss to seasoned hardwood products ranges from 10 to 50 per cent, sometimes representing a loss of thousands of dollars to a sino^le manufacturer or dealer who neglects to adopt the proper preventne measures. The affected articles are not only reduced in value l)ut Fig. 31. — Powder-posted sea.soned hickor.v .*tock in tht- bdsilare. A, end of bolt ; B, cud of section of bolt ; bolt rousb "l-iniagod by Xuloiiopx C, planed section of daiii:i.?ed frequently are rendered worthless for the purpostns for which they are intended. In the aggregate the direct financial loss that has been caused by these beetles in this country has amounted to hundreds of thousands of dollars. The loss increases Avith the length of time the infested stock is held in storage ; the wood may be reinfestcd by many 30 BULLETIN 1490, U. S, DEPARTMENT OF AGRICULTUEE generations oyer a period of 20 years or more. In certain cases powder-post injury may be a menace to human life, as in the weakened woodwork of buildings, vehicle stock, or ladders. Losses due to Lyctus beetles can be prevented by proper methods of classification and piling of stock by kinds ; by keeping heartwood Fig. 32. — A, Dutili plywood, imported from the Philippine Ishinds, powder-posted by Bostrychopsls parallela ; B, bostrichid powder-post iujury to myrtle iu Oregon and sapwood stock sei^arate; by periodical inspection, utilizing the older stock first (-i^) ; and by using only heartwood piling sticks; or by submergence in water for four months, which renders the wood immune from attack, even after removal from the water. In the case of finished wood products, it may often be practicable to treat the wood with substances to prevent attack. Creosotes are DEFECTS IX TIMBER CAUSED BY INSECTS 31 effective preventives, can not be used, in manner of the laying of the eggs in tlie pores of the wood, any substances that will close the pores will prevent oviposi- tion in wood not pre- viously infested. In wood from .which bee- tles have emerged, however, eggs might be laid within the exit holes. Paraffin wax. varnish, linseed oil, or other fillers effectively close the pores of wood. A certain var- nish known as hard- ened gloss oil is com- monly used. Wood that has been sea- soned less than 8 to 10 months will not be attacked by Lyctus beetles ; therefore, in applying chemical preventives, only sap- wood that has been seasoned for 8 to 10 months and longer need be treated. The seasonal history of these beetles indicates that preventives should be applied be- fore March 1. The great and re- curring expense of treating infested Avood can be avoided by prevention of attack by proper methods of management. Since only the sapwood or whitewood is attacked but they stain the wood ; hence, where they the light of the discovery of the place and J.-,,;, :;:-; — iinlt> iiiiiil.- li\ tlir liainled :ish liorer {^lncll|tus caprcHU). one of the puwder-post beetles Fig 34. — Powder-pusieil ash ing coarse powdery frass Keoclytus capraca shipbuilding luui: iu the buiroWB uiadf by by Lyctus powder-post beetles, it is recom- mended that more heart wood be used to n j. ., * j • -f^.. whif*. replace sapwood. Although the demand of the trade is foi AUnte- wood handles, etc., the prejudice agamst heartwood is not wan anted 32 BULLETIN 1490, U. S. DEPARTMENT OF AGRICULTURE and should be overcome by educational propaganda. Weight for weight, red or heartwood hickory is as strong as white or sapwood. Closer utilization can be effected by larger use of heartwood. Some manufacturers paint their stock, to overcome this trade prejudice. Effective remedies include kiln-drying at high temperatures (180° F. and over) ; steaming at 130° F. (this will not^ insure against future attack) (46,47) ; and treatment with orthodichlorobenzene or a mixture of kerosene and coal-tar creosote, after which the material should be kept in quarantine a sufficient length of time to deter- mine whether a second ffT'^'Sji ' .-'''"^■■■■■■■■l treatment is required. Partially damaged material which is too valuable to be de- stroyed should be sal- vaged, when practi- cable, by trimming off and burning the sap edges and other dam- aged and infested parts. POWDER POST CAUSED BY PTINIDAE AND ANOBI- mAE This damage con- sists of small holes one-sixteenth to one- eighth of an inch in diameter and irregu- lar burrows in the wood of both soft- woods and hardwoods (fig. 30). The dam- age is similar to that caused by Lyctus bee- tles, except that softwoods are also attacked and the defect occurs -^ in the heartwood. Most injury by Ptinidae is caused to seasoned wood, or logs that have been left lying in the woods too long. Fui -l^owder-postert southorn yellow pino damaged by Hplotrupes bajulus lioards POWDER POST CAUSED BY BOSTRICHIDAE This damage consists of circular holes one-eighth to three-eighths of an inch in diameter and irregular longitudinal burrows filled with frass, or with coarser dust in the sapwood and heartwood of hard- woods, which does not fall out so readily. (Figs. 31 and 32.) These insects -^ attack freshly felled logs with the bark on. The eggs are laid within the log near holes made by the adult beetles. Submerging the logs in the mill pond and prompt utilization will ])revent much loss. In the case of vehicle, handle, and similar -^ This defect is caused by Xyletinus peltatua Harris, which attacks both hardwoods and .softwoods. 2-» Bostrichidac^ : Scobicia, Xylobiops, etc. DEFECTS IN TIMBER CAUSED BY INSECTS 33 stock, all the bark and edgings should be removed ; treatment with shellac or wax will also prevent the adult beetles from boring into the wood to lay eggs. ^ POWDER POST CAUSED BY ROUND-HEADED BORERS (CERAMBYCIDAE) Holes about one-eighth of an inch in diameter, tightly packed with finer frass, in the sapwood or heartwood of oak and hickorv. are made by the flat powder-post beetle.^^ It attacks both freshly cut and seasoned timbers and continues to work for a number of years. Damage can be pre- vented by prompt han- dling of the logs, re- movel of the bark, and disjjosal of infested stock. Oval holes about one- fourth of an inch in diameter or irregular burrows tightly packed with coarse, powdery frass, in the heartwood and sapwood of ash, are caused by a round- headed borer.-'' (Figs. 33 and 34.) This in- sect attacks only freshly cut timbers, but when infested logs are stored the borers continue to work for several years Prompt utilization, submerging the logs in the mill pond, rapid seasoning, or removal of the bark will pre- vent this defect. Tim- ber should be felled in the late fall or winter, so that the bark may dry somewhat and be less attractive to the beetles when they are flying and depositing their eggs early in the spring. In the Gulf States logs should not be allowed to lie in the woods at any time for more than two to three weeks, or after the 1st of April farther north, nor should they be .-♦w^"^' "1? ,-^ k ..►■ii n|in'i|»fni'H ""**j Fig. 36. — Ring distortions in balsam caused by tbe spruce bud worm. Base of tree- attacked in 1911 sbowed accelerated growth for two years, followed by retardation and incomplete ring in 1!)18 (X), and rapid recovery later. ('/?!) -^ Smodicum cucujiforme Say. "' Neoclj/tu^ capraca Say. 34 BULLETIN 1490, U. S, DEPARTMENT OF AGRICULTURE stored in closely packed piles for lonecially hickory, ash, and oak woodwork of farming machinery and implement handles (see illustration on title-page, and figs. 1, 2, and 3); ladder stock, as rungs, etc.; and vehicle stock, as hubs, spokes, felloes, rims, singletrees, poles and shafts. Other products affected include woodwork of electric street cars; shipbuilding lumber (fig. 4) ; the Army and Xavy stores of han- dles, tent poles, wheelbarrows, oars, and many other hardwood articles; interior finish or trim and ornamental woodwork, as panels, mantels, doors, doorposts, staircases, wainscoting, flooring, etc.; construction timber, including beams, joists, roof framing, etc.; furniture, including tables, chairs, bureaus, cabinets, refrigerators (before use), filing cases (fig. 5), piano stock, bookcases, cabinet- work, etc. ; inside rustic work ; wood specimens and curios in museums; cooperage stock (barrel-stave bolts); shoe-last blocks; walking sticks, umbrella handles, measuring rules, and blocks to be converted into golf-stick heads; fish-net hoops; ornamental bamboo (fig. 6); Japanese fans; shuttle blocks, and "picker" sticks (for driving shuttles in looms) , etc. Hickory, ash, and oak are the kinds of wood most liable to injury, but persimmon, osage orange, black walnut, butternut, maple, elm, wild cherry, locust, poplar, sycamore, eucalyptus, sassafras, orange wood, fig, bamboo, and other woods are also attacked. POWDEK-POST DAMAGE BY LYCTUS BEETLES. Fig. 1. — Powder-posted ash shovel handle, showing exit holes of adult beetles ; the work of Lyctus planicoUis. (Original.) PAEMERS' BULLETIN" 778. Fig. 2. — Powder-posted ash shovel handle with surface wood cut away to show burrows or larvie withiu ; work of Lyctus planicollis. (Snyder.) POWDER-POST DAMAGE BY LYCTUS BEETLES. 7 EXTENT OF LOSSES AND THOSE UPON WHOM THEY FALL. Powder-post causes a loss which falls alike on the dealer, the manu- facturer or owner, and the consumer of finished products. The pro- ducer of the unseasoned or crude product is not affected, because it is only after the wood is seasoned a year or more that it is attacked and damaged by these insects. Second-growth sapwood of the best Fig. 3. — Powder-posted hickory pickax liaudk-s, showing exit holes of adult beetles ; work of Lyctus linearis. (Original.) quality is particularly liable to attack and serious injury, especially when it has been stored or piled in one place for two or three years or more. The loss to seasoned hardwood products ranges from 1 to 50 per cent, sometimes representing thousands of dollars to a single manu- facturer or dealer who neglects to adopt the proper preventive meas- ures. The affected articles are not only reduced in value, but fre- quently are rendered worthless for the purposes for which they are intended. In the aggregate the direct financial loss that has been 8 PAEMEES' BULLETIN 778. caused by these beetles in this country has amounted to hundreds of thousands of dollars annually. The loss increases with the length of time the infested stock is held in storage. In certain cases powder-post injury may be a menace to human life as in the weak- ened wood material of vehicles, ladders, etc. CHARACTER OF THE INSECTS WHICH CAUSE THE DAMAGE. The Lyctus beetles are small, slender, somewhat flattened, brownish to nearly black beetles, which, upon emerging from the wood where f •. k.f {. ^t> \H *■ «# « '» t , ■ i Fig. 4. — Powder-posted white ash shipbuilding lumber, showiug burrows of larvis and exit holes of adult beetles ; board from closely piled stack of lumber throughout which larvae had burrowed; work of Lyctus planicolUs. (Original.) they breed and pass the winter as larva?, fly or crawl about in search of suitable wood material in which to deposit their eggs. HABITS AND SEASONAL HISTORY OF LYCTUS BEETLES. There are four stages in the life history of these insects — namely, the egg, the larva or grub, the pupa or resting stage, and finally the adult or beetle. The egg (fig. 7) is deposited in the pores of the wood by the female beetle soon after it emerges from the Avood. The minute larva which hatches from the egg proceeds to burrow in and through the wood in all directions, feeding and growing as it proceeds, until it has attained its full size. The full-grown larva (fig. 8) is a yellowish- white grub ranging in length from one-eighth to one-fifth of an inch, POWDER-POST DAMAGE BY LYCTUS BEETLES, with three pairs of legs, and Avith the tip of the body curved under toward the head. Upon reaching maturity as a larva it excavates a cell at the end of its burrow (fig. 9), and in this transforms to the pupa (fig. 10). Later the pupa changes to the adult beetle (fig. 11), which can fly in search of suitable places to lay its eggs. 1 ■' : ; i; , i'; ■(.'' '1 -jr ''1 m i 1 ^^P i ^3 p^H [m 1 • J i Wv ijfl^B ''ft 1 ri I j9 i^^^n ^tH^I ^^^^Bi . i PI 'J ■ ! 1 ^m wm. '*' jfiljf - hjjL.: Fig. -Powder posted oak file case, showing Lyctus planicollis. exit holes of adult beetles ; (Original.) work of Seasoned wood is attacked by these beetles because the chemical changes which take place in the process of seasoning render the nu- tritive substances in the wood, such as sugar and starch, especially suitable as food for the development of the young or larval stage. Each female beetle deposits many eggs,^ and many females oviposit in a single piece of wood, so that the combined work of their nu- 1 A large female of Lyctus planicollis Lee, about one-fourth inch in length, that was dissected contained ovaries as two separate, elongate ovate clusters one-tenth inch in length, one of which was al)Out one-third the size of the other. These ovaries took up most of the space of the abdomen. The eggs were arranged in rows so as to have the ap- pearance of being braided. The mature ovules, or fully formed eggs, are pointed at one end and rounded at the other, with the rudimentary strand present at the rounded end. The egg surface is apparently granular. At least 40 eggs were in the larger mass. 61165°— BuU. 778—17 2 10 FARMERS BULLETIN 178. merous progeny, burrowing through the wood in quest of food for their development, results in the complete destruction of the inte- rior wood fiber and its conversion into a mass of fine powder. If the first attack and the first generation do not accomplish this de- struction, subsequent generations will follow in the same wood until nothing of the solid fiber is left but a thin outer shell. Fig. 6. — Powder-posted ornamental section of bamboo, showing exterior and interior of split bamboo; work of Lyctus parallelopipedus. (Original.) The different kinds of Lyctus beetles vary somewhat in their habits and seasonal history, but there is a general similarity. They pass the winter as larvae in the wood, change to pupae in the early spring, and during late spring and early summer the adult beetles emerge from the wood and fly about. Under natural out-of-door conditions the eggs are laid in the pores of the wood soon after activity commences in the spring, but in storehouses, sheds, or build- ings kept warm and dry, the development may take place and the eggs may be deposited much earlier. POWDER-POST DAMAPiE BY LYCTUS BEETLES. 11 The larviic remain dormant or active in the Avood, according- to the temperatnre of the phice -where stored, and in conse(|nence infestation in wood stored in cold ph\ces may pass nnnoticed. If the wood is re- FiG. 7. — Egg of a powder-post beetle, Lyctus planicoUis, in pore of wood on radial section of ash ladder-run^ (Snyder.) stock ; pore opened to show eg Highly iiiaguified. moved from outdoors, open storage sheds, or other places which are cold in winter, to the dry kiln, the dormant larvse start to work in the wood, as shown by the ejection of boring dust or powder. Handling or jarring infested wood appears tempo- rarily to stop the activity of larvae contained in it. In general, the adults or beetles are active be- tween the first of March and the last of July at "Washington, D. C. (about latitude 39° and longi- tude 77°, and practically at sea level), but the period varies according to the species, the tem- perature of the storerooms, and the geographical location. According to the senior author, the vari- ation due to latitude, longitude, and altitude from a date at Wash- ington, D. C, will be approximately four days for each degree of latitude, 5° of longitude, and 400 feet of altitude, being earlier in the season southward, westward, and descending. The number of adult beetles that might be active and deposit eggs after the last of July at Washington, D. C., is so insignificant that practically no damage is done by them. Therefore the danger of attack would be over relatively earlier at parts south of Washington and west- ward, and later northward. The approximate dates of flying and Fig. 8. — Larva of a powder -post beetle, Lyctus plaiiicollis. En- larged. (Chitten- den.) 12 FAKMERS' BULLETIN 778. egg laying by each species under outdoor conditions at Washington, D. C, are given on pages 13, 14, and 15, So far as laiown there is only one generation annually. THE FOUR SPECIES RESPONSIBLE FOR MOST OF THE LOSSES. While, as previousl}^ stated, there are many species of Lyctus beetles in tlie United States, the European Lyc- tus, the southern Lyctus, the velvety Lyctus, and the western Lj^ctus are the four species responsible for prac- tically all the losses. THE EUROPEAN LYCTUS.* The European Lyctus beetle is rusty red-brown, slender, somewhat flattened, elongate, and from one- tenth to one-fifth inch in length. The wing covers have single rows of large, rounded, ver}^ shallow punctures. This species is commonly met with in northern Europe under natural conditions as well as in commercial products, especially in England, France, and German3^ Therefore it is evident that it was introduced into this countr}^ from Europe. In addi- tion to the w i d e distribution of this species in the tem- perate zones of the world, it is espe- cially common and destructive in the States north of North Carolina, Tennessee, and Ar- kansas. There are a great many rec- ords of damage to seasoned hardwood products by this beetle from this area, includ- ing Maine, Massachusetts, New York, Pennsylvania, Virginia, * Lyctus linearis Goeze. Fig. 9. — Pupal cells of Lyctus plani- collis in powder posted wliite-ash shovel handle. (Snyder.) Fig. 10. — Pupa of a powder-post beetle, Lyctus planicolUs. (Chittenden.) POWDER-r'OST DAMAGE BY LYCTUS BEETLES. 13 West Virginia, Ohio, Indiana, Illinois, Missouri, loAva, Michi- gan, and Minnesota. The great number of specimens in the col- lection of the United States National Museum show but a single record from the South Atlantic and Gulf States, and this is evi- dently a temporary introduction. Undoubtedly the species is fre- quently carried into the southern region, but evidently it does not survive there. This beetle is common in commercial products of seasoned hickory, oak, walnut, and ash, and occasionally in poplar, wild cherry, and locust. It is not i-ecorded from natural growth in the open in this country, but is said to infest such growth, as well as commercial products, in Europe. Adults of the European species, which has been shown to have a relatively northern distribution in the United States, begin activity as early as the first part of March in its southern distribution and are still active during the first part of August in its northern distribution, general emergence of the adult beetles from infested wood occurring at Wash- ington, D. C, from April until June. The eggs are deposited soon after the adult beetles emerge and are inserted into the pores of the wood by means of a long, slender, flexible ovipositor. The winter is passed in the larval stage in the wood. General pupation occurs from about the middle of April to the first of May in the District of Columbia. THE SOUTHERN LYCTUS.^ The southern Lyctus beetle is pitchy black, slen- powder-post beetle, der, somewhat flattened, elongate, and from one- Lyctus piamcoius. tenth to one-fifth inch in length. The wing covers have smaller, finer, and deeper punctures in more or less distinct double rows. Individuals of this species vary extremely in size, and there is marked difference in size between the sexes, the males often being much smaller than the females. As the result of con- tinued breeding in the same wood for several generations, in confine- ment the beetles were found to decrease in size. This species is injurious to hardwood products in and from the South Atlantic and Gulf States to California, Arizona, and Nevada. This range probably represents the natural distribution of this south- ern species. It is frequently introduced into the Northern. Central, and Western States and transported to other countries, but this appar- ently never results in its permanent establishment except in warm storehouses. There are definite records of its occurrence at Cape ^ Lycius planicolUs Lee. 14 farmers' bulletin 778. Town, South Africa, in lumber received from the southern United States, and at Buenos Aires, Argentina, in the ash wood in refrigera- tors and shovel handles from the United States. The southern Lyetus has been recorded as breeding under natural conditions in this country and is common in the Southern States in conmiercial products, such as seasoned ash, oak, hickory, persimmon, and sycamore. Rearing records show that it may breed continuously in the same wood during a period of at least six years, or until all the wood tissue has been converted into powder. The beetles emerge from infested wood of commercial products in heated buildings much earlier than where exposed to outdoor conditions. Owing to the character of the class of commercial products infested by Lyetus beetles, which are often stored indoors, there apparently are no great differences in the periods of activity of adults of species of northern and southern distribution. Adults of this southern species are active from the middle of Feb- ruary till the last of September in the South Atlantic and Gulf States. General emergence of the adult beetles and mating occur from the middle of April to June, and very few beetles emerge at Washington, D. C, after the first part of July. Egg laying occurs a feAV days after emergence, and the eggs hatch after a period of not longer than 10 daj^s. The wdnter is passed as larvae in the wood, and full-grow'n larvae are in the pupal cells at Washington by the first part of Feb- ruary. General pupation of the larvae in the infested wood in rear- ing experiments at Falls Church, Va., occurred from about the mid- dle of March to the first part of April. THE VELVETY LYCTUS.i The velvety Lyetus is rusty red-brow^n to black, slender, flattened, and elongate, and from one-twelfth to one-sixth inch in length. The punctures on the wing covers are very fine and obscure and not placed in rows; the fine, dense, yellowish hairs on the wing covers are prominent, which gives the beetle a velvety appearance. Extensive observations have been made on the habits of this spe- cies, which has been recorded as injurious in Texas, Louisiana, Florida, Georgia, South Carolina, Virginia, West Virginia, District of Columbia, Long Island, New York, Ohio, and ^Missouri. The natural distribution of the species -is evidently in the South Atlantic and Gulf States and in part of the Mississippi and Ohio River Valleys, from which it has been temporarilj^ introduced into other States. This beetle infests the seasoned sai:)wood of commercial products made from persimmon, hickory, ash, oak, and bamboo; it also lives ^ Lyetus parallelopipedus Melsh. POWDER-POST DAMAGE BY LYCTUS BEETLES. 15 in the dead wood of natural growth of osage orange, sassafras, and fig. Adults of the velvety Lyctus are active from the middle of March till the last of August at Washington, D. C, General emergence occurs from June to the last of July. THE WESTERN LYCTUS.i The western Lyctus is a rusty red-brown, slender beetle, somewhat flattened and elongate, and from about one-seventh to about one- fifth inch in length; the punctures on the wing covers are very fine and placed in more or less distinct double rows. This species is recorded from California in commercial products, seasoned orange wood and hickory, tanbark oak, and cordwood of live oak. Adults of this species are active from April till the middle of September. CONDITIONS FAVORABLE FOR ATTACK. Second-growth white wood or sapwood of the finest qualit}^ of hardwoods, especialh' hickory, ash, and oak, which has been stored or piled in one place for two or three years or longer is esi>ecially liable to damage by Lyctus beetles. This is particularly the case if the material has not been handled or moved and if the old stock is allowed to accumulate. Refuse and useless sapwood material and infested stock piled about the sheds or j^ards, sa]:)wood piling sticks, etc., are sources of infestation. If the different species of hardwoods are not placed in separate piles, the species of woods not so liable to attack often become infested. CONDITIONS UNFAVORABLE FOR ATTACK. Material of species other than hickory, ash, and oak is less liable to attack. Sapwood seasoned for less than 8 to 10 months will not be attacked, and heartwood is never' attached- (fig. 12). The conditions will be rendered \Qvy unfavorable for attack by powder-post beetles wherever hardwood stock in yards and store- houses is handled as follows : Material inspected and rehandled an- nually, preferably in November and February, and that showing evidence of powder-post attack sorted out and burned: all refuse and useless sapwood material burned; as far as practicable, all dry or seasoned hardwood stock separated into heartwood, pure sapwood, and part sapwood, and into hickory, ash, oak, etc., and classified ac- cording to the number of years it has been seasoned, and the oldest "^ Lycitts caricollis Lee. = Exhaustive strength tests conducted by the Forest Service show that the heaviest, and consequently the strongest, hickory averages below 10 rings per inch in rate of growth, and that, weight for weight, red hickory (heartwood) is as strong as white hickory (sapwood). 16 FARMERS BULLETIX 778. stock utilized and sold first; accumulations of refuse material in which the insects could breed prevented; the introduction into lum- FiG. 12. — rowder-posted sapwood oak veneer laid on a core of chestnut (door stock) ; ■work of Lyctus planicoUis. Note that the heartwood oak and the chestnut have not been attacked. (Oi'iginal.) ber yards and storehouses of material infested with powder post prevented; and, finally, heartwood instead of sapwood piling sticks used in the piles. POWDEE-POST DAMAGE BY LYCTUS BEETLES, INSECT ENEMIES OF LYCTUS BEETLES. 17 There are many insect enemies of powder-post beetles. Among the beetles, species of the familj^ Cleridae are often beneficial in checking the multiplication of Lyctiis beetles, the larvae preying on the Lyctus larva} and the adults preying on the Lyctus adults. Other beetles which commonly prey upon the powder-post beetles belong to two other families.^ Fig. 13. — Exit holes of small, four-winged, wasplike parasites of Lyctus in powder-posted red oak interior finish. (Original.) Many species of small, four-winged, wasplike parasites have the Lyctus beetles as their hosts. The emergence or exit holes of the adult parasites (fig. 13) are much smaller than those made by the beetles, but are often mistaken for those made by young Lyctus larvse. ^ Histeridae and Cucujidae. 18 farmers' bulletin 1*js. In general, these insect enemies, although beneficial, can not be depended upon to keep the destructive beetles under control, and therefore usually can be disregarded when practical control measures are being instituted. METHODS OF CONTROL. The methods of combating this class of insects and of preventing losses from their ravages come under two primary heads: (1) The destruction of the insects, or remedies, and (2) prevention of attack. REMEDIES. Infested material, including infested sap edges of lumber, etc., and all refuse sap wood in which the insects might breed should be eliminated by sorting it out and disposing of it by burning or other- wise. All material showing the slightest evidence of powder-post damage should be discarded and destroyed, except possibl}^ such articles as laaj be tested for required strength and found to be of sufficient value for retention after treatment. Material slightl}^ infested and damaged should be treated Avith kerosene oil, after which it should be kept in quarantine a sufficient length of time to determine Avhether a second treatment is required. All partially damaged material, such as the sap edges of lumber and parts of other material too valuable to be destroyed, should, when practicable, have the damaged and infested parts cut away and burned. The work should be done between October and the first of March in storehouses, and before the first of April in the open. If this is thorough]}' done and, b^^ annual inspection thereafter^ infested ma- terial is disposed of as soon as found, there will soon be no trouble from this source, unless there is a continued introduction in lumber and material received from other yards and localities Avhere methods of control are neglected. To avoid this, all material should be care- fully inspected before shipment, or at least before it is placed in the 3^ards or storehouses. TMiere it is not practicable to remove the infested parts, or in case of the more valuable stock, the wood should be subjected to methods of treatment for the destruction of the insects between October and the first of ISIarch. Of the following remedies, that most suitable in each case should be selected, remembering that the treatment must not be detrimental to the wood for subsequent uses. (1) Liberal applications of pure kerosene oil with a brush, or immersion of infested wood in vats of kerosene. The only objection to kerosene is the fire risk. However, kerosene soon evaporates, so that the treated material is not long near the danger point. Kero- POWDER-POST DAMAGE BY LYCTUS BEETLES. 19 sene oil does not affect the application of shellac or varnish ; the onh' effect on finishing is to make it more difficult to stain kerosene- treated sapwood to match the rest. (2) Mixtures of 3 parts creosote and 1 part kerosene oil; 3 parts kerosene oil and 1 part creosote (to obtain a deeper penetration) ; and 1 part creosote and 3 parts naphtha have been used successfully. The wood should be dipped in vats of preservative, preferably heated by coils of steam pipe, or the preservative may be applied hot with a brush. Of courHe., mixtures containing kerosene oil should not he heated over a direct fre. (3) Thorough steaming of the infested wood in a tight room or under pressure. Steaming under pressure weakens and discolors the Avood and should not be applied to wood to be used for fine finish or where strength is essential. (4) Subjecting seasoned wood to temperatures over 200° F. in dry kilns. (5) Fumigation of infested wood in tightly closed drying rooms with the fumes of sulphur at the time of the emergeiice of the adult beetles. This has been recommended for killing the beetles and preventing (i^g laying. The objection to treating infested material lies in the fact that if it is once infested it may he damaged heyond repair and not safe for future use. A hreak might result in a serious accident and reflect on the refutation of the manufacturer or distrihutor. PREVENTION OF DAMAGE. By tlie adoption of the following svstem of inspection, classifica- tion, and the proper disposal of the seasoned sapwood of hardwood stock, loss by powder-post beetles can be prevented : (1) Inspect material in yards and storehouses annually, especially stock two or more years old, prefera' ly in November and February. Then (a) sort out and burn material showing evidence of powder- post attack and (b) burn all useless sapwood material. (2) Classify all dry or seasoned hardwood stock as (a) hickory, ash. oak. etc. ; (b) heartwood, pure sapwood, and part sapAvood ; and (c) according to age, that is, the number of years it has been seasoned. (3) Utilise or sell oldest stock on hand first. Prevent the accu- mulation of old stock; in other words, keep the stock moving. (4) Prevent the accumulation of refuse material in Avhich the insects can breed. (5) Use only heartAvood piling sticks in lumber piles. (6) Inspect all ncAv stock to preA'ent the introduction into lumber yards and storehouses of powder-posted material. (T) If the beetles have not been eliminated from the yards and storehouses, stock that has been seasoned longer than eight months, 20 FAEMEES' BULLETIN "778. and which is to be held in storage, may be rendered immune by treat- ing it with two coats of boiled linseed oil applied hot, or it may be immersed in vats of hot oil. The boiled oil will dry more rapidly than the raw linseed oil, especially if kerosene is added^to the hot oil. The wood should be treated between October and the 1st of March. Linseed oil has an advantage over other substances in that it can also be profitably applied to' unseasoned timber, since it will prevent checking in seasoning. This oil stains the wood slightly yellow. In case of wagon stock, however, it can be used without prejudice to the trade and is an effective preventive. Creosotes can be effectively used in case of stock to which the brown stain will not be detrimental. The wood should be dipped in vats of hot creosote, or the preservative should be applied hot with a brush. In case of finished products or more valuable material, any sub- stance which closes the pores of the wood may be effective^ applied. For example, paraffin wax, varnish, etc., effectively close the pores of the wood and prevent the beetles from depositing the eggs, which are laid in these pores. Thus the sapwood portions of backs and interior surfaces of cabinet work, inside finish, and furniture, etc., should also be treated to prevent attack. In conclusion it may he stated that while there are a numher of effective chemical ireatTnents to 'prevent attach^ and to kill the insects after they get into the \oood^ the great objection to all- of them is the great and recurring expense of treating material that never would le attacked if^ by the proper methods of management, the premises were kept free from the pest. o U. S. DEPARTMENT OF AGRICULTURE FARMERS' BULLETIN No. 1582 PROTECTION OF LOG CABINS, RUSTIC WORK AND UNSEASONED WOOD INJURIOUS INSECTS INSECTS cause considerable damage to the un- barked logs of the principal woods used in the construction of log cabins, rustic woodwork, and certain other unseasoned products. This damage, which varies from the making of numerous holes in the bark to the complete destruction of the sapwood and heartwood, causes annoyance and unsightly con- dition of the material as well as large financial loss. Some of the insects which cause the damage arc active nearly every month of the year except Decem- ber, January, and February. It has been found that by cutting the trees at certain seasons and by treat- ing the wood with preventive and remedial sub- stances practically all such insect damage can be prevented or checked. This bulletin tells how it can be done. Although the information contained herein applies specifically to the insects which occur in the eastern and southern parts of the United States, the princi- ples set forth can be applied equally well to prob- lems of this nature which occur in the countrj'^ as a whole, provided due allowance is made for individ- ual differences in insect and tree species and also in the time of flight of the beetles because of differences in climate. Washington, D. C. Issued July, 1929 PROTECTION OF LOG CABINS, RUSTIC WORK, AND UNSEASONED WOOD FROM INJURIOUS INSECTS By R. A. St. George, Associate Entomologist, Division of Forest Insects, Bureau of Entomology How beetles and grubs damage unseasoned wood 1 Woods principally used for cabins, rustic work, and certain wood products 1 Classes of insects responsible and the damage they do 2 Bark beetles 2 Ambrosia beetles 4 Wood borers 4 Seasonal activity of the insects 11 Page Conditions favorable and unfavorable for attack 14 Conditions favorable for bark beetles and ambrosia beetles. 14 Conditions favorable for powder -post beetles... 14 Conditions favorable for roundheaded borers and flat-headed borers _.. 15 Preventive and control measures 15 Prevention of attack.. _ 15 Treatment after attack 18 DURING the last few years there has been an increasing demand for information on the protection of log cabins and rustic work from injurious insects. This is largely due to the popularizing of National and State forests and parks for recreational purposes, as a result of which many rustic bridges, benches, and log cabins have been constructed in such places. But it is also due to the increased building of rustic summer homes and arbors on private woodlands and estates. Wood with the bark still on is subject to injury by many kinds of beetles; therefore manufacturers, as w^ell as the users, of rustic furni- ture constantly request advice. In addition, concerns requiring small raw poles from which to manufacture certain finished products, such as shuttle blocks, mallets, and mauls, often suffer severe losses and call for advice. HOW BEETLES AND GRUBS DAMAGE UNSEASONED WOOD Woods cut at certain seasons of the year are subject to attack by beetles which fill the bark with holes, thus causing sawdustlike borings to fall out and lodge on the wood. The larvae, or grubs, of wood-boring beetles mine the inner bark, causing the bark to loosen and fall off, and they bore into the sapwood and sometimes the heart- wood of logs, making large holes and often reducing them almost to dust within a few months, before the wood becomes well seasoned. WOODS PRINCIPALLY USED FOR CABINS, RUSTIC WORK, AND CERTAIN WOOD PRODUCTS The woods mainly used in the construction of log cabins and the rustic work in summer homes, furniture, and fences are spruce, fir, hemlock, tamarack, cedar, juniper, pine^ birch, poplar, hickory, and 1 FARMERS" BULLETIN 15 82 oak. The selection of the wood to be used for these purposes is often determined to a large extent by the local suppl3^ Hickory, ash, dog- wood, and persimmon, which are used in the manufacture of shuttle blocks, mallets, mauls, etc., are cut under very similar conditions and thus are subject to similar attack, and the protective measures de- scribed in this bulletin are equally applicable to stock cut for such purposes. Those woods which are probabh' most subject to insect attack and subsequent damage, if cut during certain seasons of the year, as explained on pages 14 and 15. are hickory, pine, persimmon, spruce, ash, and dogwood, although the others mentioned are b}^ no means immune. The damage can be largely prevented if proper measures are taken. From the standpoint of durability cedar, junii^er, and white oak are probably the most desirable of the woods listed above, especially where the wood comes in contact with the ground.^ CLASSES OF INSECTS RESPONSIBLE AND THE DAMAGE THEY DO The insects responsible for damage, in cases where the bark remains on logs used in rustic work, can be conveniently grouped into three main types or classes, according to their structure and the character of their work, n a m e 1 y, bark beetles,- ambrosia beetles,- and wood borers.^ The bark beetles confine their activities to the bark and burrow between it and the sapwood, often scoring the latter, the ambrosia beetles bore directly through the bark into the sapwood and sometimes the heartwood, and the wood borers may penetrate all three parts of the log. All three classes of these insects have four distinct stages, namely, the egg; the larva, also called worm or grub; the pupa, or transform- ing stage; and the adult, or beetle stage. Only the larval and adult stages are responsible for damage to woodwork. In all instances the larvae hatch from eggs laid by the beetles. After the larva becomes mature it makes a cell in which to rest, called the pupal cell, and there becomes a beetle. FiGLKE 1. -An iidvilt bark beetle, Ipti avulsus Eich. Enliuged 18 diameters BARK BEETLES The adult insects of the first class, the bark beetles, are short, cylindrical, reddish-brown to black insects, varying in length from about one-sixteenth to one-fourth inch. (Fig. 1.) They bore ^ The United States Forest Service has conducted extensive tests and made detailed studies of the durability and chemical preservation of wood and should be consulted if further information of this character is desired. = Order Coleoptera, family Scolytidae. P Order Coleoi)tera, families Cerarobycidae, Bostrichidae, and Buprestidae, PROTECTION OF LOG CABINS, ETC., FROM INSECTS 3 through the outer bark to its soft inner portion, called the phloem, where they make tunnels of various types, along the sides of which they lay their eggs. (Fig. 2.) It is while the beetles are boring through the bark and constructing their tunnels that they push out to the entrances the fine brownish-white sawdustlike particles, or frass, which falls on the wood below and attracts attention by its unsightly appearance, and it is this tunneling that causes the bark Figure 2. — Tunupls of adults and larval galleries of a bark beetle, Leperisinus aculcatus Sav. beneath the bark of ash. Natural size. The frass that was in the galleries of this species adhered to the bark when it was removed to loosen and fall off. The piles of frass on a log enable one readily to detect the presence of bark beetles within it. The larvae or grubs are tiny, whitish, cylindrical, slightly curved, legless creatures. (Fig. 3.) Upon hatching from the eggs, they extend their mines in all directions, quite often at right angles to the original (parent) tunnel, thereby aiding in the loosening of the bark. The galleries often contain "borings or frass. This depends upon the species of bark beetle. TARMEES' BULLETIN 15 82 Figure 3. — Larva or grub of a pine bark beetle {Ijjs sp.). Enlarged 10 diameters AMBROSIA BEETLES The ambrosia beetles (fig. 4) or pinhole borers, which are the adults of the second class, closely resemble the bark beetles in gen- eral appearance. Their work differs considerably, however, and can easily be distinguished. After the ambrosia beetles enter the bark they bore immediately into the sapwood and sometimes into the heartwood, where they extend their galleries in all directions, each making a hole about the size of a pinhead. (Fig. 5.) While boring these tunnels they push out sawdustlike par- ticles, which either fall out loosely in piles (fig. G)', or come out in stringlike masses (fig. 7) as if being squeezed from a tube. These borings are white, whereas those of the bark beetles are usually brownish and fall loosely from the holes in the bark. In cer- tain cases much of it, however, remains in the tunnels. The galleries of the ambrosia beetles are round, always free from borings, and quite often their walls are stained black. Their food is not the wood, but a substance called " ambrosia," which is a coating formed of a minute fungus that is propagated by the beetles themselves. It is this that stains the walls of their gal- leries.* The damage by these borers is caused almost entirely by the adult beetles, as the larvae, until mature, stay either in the original gallery or m separate cells where they are in most cases cared for and fed by the beetles. Beetles of this group do not often cause much damage to wood after it has been put into log cabins or rustic work if the trees are cut in the fall of the year, be- cause then it has seasoned by the time the beetles are flying and is too dry to be in a suitable condi- tion for them to work in it. If the wood is cut green, however, and is used during the period of insect activity, it may be attacked im- mediately by the beetles, in which case a considerable quantity of boring dust will be exuded. WOOD BORERS The adults of the wood borers do not as a group present so uniform an appearance as do the bark beetles and ambrosia beetles. The * Hubbard, H. G. ambrosia beetles. U. S. Dept. Agr. Yearbook 1896 : 421-430, illus. 1897. Figure 4. — An adult ambrosia beetle {Xylcborus sp.). Enlarged about 14 diameters PROTECTION OF LOG CABINS, ETC., FROM INSECTS Figure 5. — Work of adult ambrosia bt't-tlos (Xylotcnts sp.) in pine. Two-thirds natural size Figure G. — Pilps of boring dust or frass being pushed out as ambrosia beetles (Gnathotrichus sp. ) are entering a hickory log. About one-third natural size FARMEPiS' BULLETIN 15 82 wood borers may be divided into three subgroups, namely, powder- post beetles, roundheaded borers, and flat-headed borers. I'OWDER-POST BEETLES The powder-post beetles are short, cylindrical, recldish-brown to black, hard-shelled insects, ranging in length from one-eighth tonearly one-half inch. In the eastern section of the United States there is only one species ^ that causes much damage to the class of materials under considera- tion. This beetle has reddish-brown markings and is about one-fourth of an inch long. (Fig. 8.) It is commonly known as the " red-headed shot-hole borer " and was mentioned years ago by C. V. Riley as doing considerable damage. It works principally in the wood of the hickory and persimmon, although it has been found in other woods. The adult bores through the bark and into the sapwood, making a cylindrical tunnel around the log just under the surface of the wood and at right angles to the grain. (Fig. 9.) The pores or cells of the wood are opened up, and the female beetle can then insert her eggs into them. The original or egg tunnel is usualy bored about 11/2 inches on each side of the entrance hole, although in some cases it may extend in one direction only. The injury can readily be detected by the loose, whitish, dustlike borings which may be found on the bark below the circular entrance hole of the parent gallery. The larva or grub of this beetle has a curved form, some- what similar in shape to that of the cut- worms found in the garden. When it is doubled up the head of the grub is close to the end of the abdomen. (Fig. 10.) This beetle, in marked contrast to the am- brosia beetles, is ex- ceedingly destructive to the wood, both in its adult ancl larval stages. In pieces of wood of small diameter it often extends its gallery or tunnel completely around the section, thus Figure 7. — Boring dust or frass which certain specios of ambrosia beetles (probably a species of Xyloterus) push out of the wood in cylindrical casts. About natural size Figure 8.- -An adult powder-post beetle, Xylobiops basilare. Enlarged 12 diameters ^ XyloMops Itasilare Say. PROTECTION OF LOG CABINS, ETC., FROM INSECTS greatlj' weakening it and causino; it to break oif read- ily. Tlie larvae also extend their work to the pith in such pieces, completely cle- stroyino- it and often liter- ally reducing it to powder. In the larger pieces of wood this insect confines its Avork more to the sapwood, and by the time the larvae are full grown they have destroyed nearly all of the sapwood. (Fig! 11.) The work of the larval borers is entirely in the interior of the log and can not be detectecl without chopping into the wood. The borings are of the same texture as those of the adult ambrosia beetles but are packed tightly in the mines behind the larvae. "When the borings are loos- ened they break up into cakes. Occasionally the in- jury is not noticed until the wood has been worked up into the finished product (fig. 12) and the emerging beetles leave holes that in- dicate the destruction which has been going on unnoticed inside of the manufactured article. Hickory and persimmon woods used in the manufac- ture of shuttle blocks, mal- lets, mauls, etc., are liable to severe injury by this in- sect, sometimes suffering a 50 per cent loss. (Figs. 11 and 12.) ROUNDHEADED BOREES FiGUliE 9. — Piece of hickory with Ihr liaiU and a little of the wood removed, rev(>nliii£;- tunnel of an adult powder-post Ijeetle, Xylobiops basilare. Entrance hole is shown at tip of arrow, and the gallery is seen extending on each side. Larvae, pupae", and emerging adults are shown in their cells. Natural size The roimdheaded borers have a remarkable varia- tion in general appearance. (Fig. 13.) The beetles range in length from less than one-fourth inch to more than li/* inches. They also vary considerably in the place and the manner of laying their eggs. The adult beetles lay (heir eggs (1) on top of the bark" (fig. 14), or (2), if the bark is ^ Chion cinctus Drury. •46814°— 29 2 8 FARMEES' BULLETIlSr 15 82 removed, occasionally on the sapwood, over •\vhicli they secrete a covering, or (3) in crevices under the bark ^ (fig. 15), or (4). through slits or pits'* Avhich they gnaw in it. (Fig. 16.) The larvae (fig. IT) which hatch from these eggs are entirely responsible for the damage caused to the wood. They are elongate, fleshy, yellowish-white grubs, usually slightly tapering toward the tail end. Upon hatching, they bore into the soft layers of the inner bark, or phloem, which they begin to mine. Some species'' confine much of their activity to mining under the bark, thereby loosening it and causing it to fall off, and they also mine in the outer sapwood. (Fig. 18.) Others make large oval mines which extend deeper into the sapwood ^° and heart wood. ^^ Sometimes the grubs completely riddle the wood within a few months, although one species ^^ has entirely diiferent habits and may continue its destructive work in the seasoned wood over a period of several years. As these galleries are often one-half inch vride and as nuich as 2 feet long, they weaken the material as well as cause an unsightly condition because of the large quantity of boring dust which many of the grubs push to the outside during the process of excavation. (Fig. 19.) Each species differs someAvhat from others in the method of pre- paring its gallery. Some grubs pack the borings, or frass, tightl}' behind them (fig. 11), while others push it out through the entrance hole (fig. 19). The composition of these borings varies from fine, white, and powdery material (fig. 11) to coarse, brownish particles (fig. 19) or shreds of wood fiber (fig. 20). These characters, combined witli the species of wood they select to work in, make it possible to determine the type of injury, and in most instances to identify the specific insect respon- sible for the damage, since each species makes a different pattern while scoring the wood under the bark or gallery of a different shape or size Avhile working in the wood. FLAT-HEADED EOREKS The beetles of the group known as flat-headed borei's are more uniform in general appearance than ai-e those of the i-oundheaded borers. They ai-e slightly flattened, metallic-colored, boat-shaped beetles which range in length from one-foui'th inch to nearly I'j inches. (Fig. 21.) '' Krocli/fus sp., CyUciie (■ry borer, Cylhne caryae, which were inserted through crevices. Enlarged 3i,^ diameters to October in the vicinity of Washington, D. C, from February to December in the extreme Southern States, and from May to Septem- ber in the Northeastern States. During this time beetles are ac- tive, looking for favorable woods on which to lay their eggs. During the rest of the year, however, certain species of these insects are relatively inactive and only a very few or no adult beetles are present. The bark beetles and ambrosia beetles are active throughout nearly the entire period within the months specified although their numbers vary a great deal within the season of ac- tivity. Insects of both the bark-beetle and ambrosia-beetle types mature very rapidly and can develop from the egg to the adult stage in from foui- to six weeks. They may have as many as three and often five generations a j^ear in certain parts of the South. Figure 16. — Egg scai) made by southern pine sawyer, Monochamtis titillator, on bark of pine. The eggs are inserted through this opening. About natural size 12 i'ARMERS^ BULLETIN 15 82 The wood borers are not active for so long a period during the season as are the other two classes of beetles and do not multiply so rapidly. Many of them have one generation a year, and others have only one every two years. FiGUiiE 17. — Larva or yrub of a roundlieaded borer, Megacyllene antcnnatus White. Enlarged 3 diameters The powder-post beetle that is most destructive flies in the vicin- ity of AVashington, D. C, mainly from the early part of May to the middle of June, the maximum emergence taking place betweefi May 30 and June 8. Occasionally a partial second generation occurs, and a few beetles emerge during the warm days of late summer and fall and may be seen in flight from August 15 until cold weather comes. The nniin brood survive the winter in the mature larval stage and do not emerge as beetles until the following May. Seasonal differences aflect the earliness or lateness of the flight period. Dur- ing the hottest part of the summer it is possible for the beetles to develop from eggs in from 60 to 70 days. The beetles of the roundheaded borers usually fly only a few weeks during the spring and summer months, in the vicinity of Washing- ton, D. C, where they have only one generation a year. Farther FiGUUE 18. — Larval mining uf a roundheaded borer, Cal- lidium antennatum, which causes the bark to tall off: A. outside of the piece ; B, inner miues of the borer, (^ne-lialf natural size PROTECTION OF LOG CABINS, ETC., FROM INSECTS 13 Figure 19.- -Boriiig dust exuded by the grub of Ci/lloie caryae as it uiiued in the sapwood of bickury. About one-sixth natural size v^~^.<^4l ^^^^S ^^^^ m 'j^^^^^^S/fff^SBSS^^K^SioKm^w^ FiGUUK 20. — Coarse shredded frass made by tlie j;riibs of the southern pine savvyc Munuchainus titillator, a roundheaded borer. Eularyed about 2 diameters 14 EARMERS^ BULlLETIN 15 82 south some species have two generations and sometimes a partial third. The flat-headed borers, as beetles, fly about the same time that those of tlie roundheaded borers appear. Some species mature in a year; others take as long as two years. CONDITIONS FAVORABLE AND UNFAVORABLE FOR ATTACK The kind antl condition of wood attacked are largely dependent upon the species of insect. Some species prefer freshly cut wood that is in a moist condition, others partly seasoned wood, and still others require wood that is dry and well seasoned. CONDITIONS FAVORABLE FOR BARK BEETLES AND AMBROSIA BEETLES Two types of insects, the bark beetles and the ambrosia beetles, attack freshly cut logs on whicli the bark remains and in which the inner bark is still white and active and the sap is still present. The ambrosia beetles, however, like equally well logs, with or without bark, that have been submerged in Avater and which after being re- moved from the water remain in a moist condition, as when they are placed on the ground in the shade. Such logs may continue to be at- tacked until they dry out. Wood that is cut during the spring and summer months, when the weather is warm and damp, ma}' be sub- ject to severe injury, especially when placed in close piles on the ground so that it does not receive sfedequate ventilation. Wood which is cut in the early fall and dried out, or seasoned sufficiently during the winter months, is in an unfa- vorable condition for attack by bark beetles and ambrosia beetles when their active season arrives. Figure 21. — Adult Leetle of a flat- headed borer, CJirysobothris octocola Lee. Enlarged 4 tliameters CONDITIONS FAVORABLE FOR POWDER-POST BEETLES The powder-post beetles prefer wood that has been cut several months. They show a decided preference for wood that is cut either in the fall and slowly seasoned over winter, or that which is cut dur- ing the active season and dried rapidly. Occasionally they attack recently cut wood, but as a rule they are unsuccessful in e.stablishing themselves in it. PROTECTIOISr OF LOG CABIlSrS, ETC., FROM INSECTS 15 CONDITIONS FAVORABLE FOR ROUNDHEADED BORERS AND FLAT-HEADED BORERS Conditions that invite attack by roundheaded and flat-headed borers vai\y considerably. Many borers prefer recently cut logs, whereas other borers attack logs which have been seasoned for sev- eral months. The manner of handling the logs after they are cut has a decided influence upon wheth- er they will ulti- mately be attacked. As each species of these beetles flies and lays its eggs during only a short period, and as each kind at- tacks only one or two kinds of wood, which must be in just the right condition to at- tract it, the danger of attack by any par- ticular kind is rela- tively small, PREVENTIVE AND CONTROL MEASURES Methods of pre- venting insect attack and the checking of subseq u e n t injury, once the log is in- f e s t e d , depend largely upon the sea- sonal history and habits of the insects involved. By taking- advantage of Avhat is known of these, the desired protec t i o n can be obtained. PREVENTION OF ATTACK SEASONAL CriTIXG FOR RUSTIC STKUCTUEES FiGLiiK 22. — Grubs of the flat-heatled borer Chalcoithoru aiKjuUcolUs Lee. Enlarged 2 diameters The logs with the bark remaining on them and poles used in the construction of rustic cabins, summer houses, fences, etc., should be cut in October or November and piled 16 FARMEES' BULLETIN 15 82 at once,^^ either off the ground or under cover, in such a manner as to offer the best facilities for the rapid and thorough drying of the inner bark before the beetles begin to fly in the spring.^* This will in almost every case j^revent their being damaged by the insects that prefer the freshly cut wood. FOR MANUFACTURED PRODUCTS To prevent injury to poles used in the manu- facture of rustic furniture, shuttle blocks, mallets, and mauls, the wood should be handled in the following manner : Restrict the cutting, as previously recommended, to the late fall and winter months, and either utilize the wood before the first flight of beetles occurs in the spring or place it under a closed cover where it will be protected from in- sect attack. In some cases screening may have to be resorted to, screen cloth having 18 meshes to the inch being used. If cutting is necessary during the spring and sum- mer months, remove the poles from the forest as fast as they are cut and utilize them at once. A few days' exposure in the forest at this time is suffi- cient for infestation to occur which may develop after the wood ha^ been manufactured into the finished product. (Fig. 12.) If the poles can not be moved at once, they can be protected for several days by being sprayed with a solution of creosote and kerosene as hereafter described. Avoid leaving about the factory yards, during the period of insect activity, waste material on which the bark remains, as it is likely to serve as a breeding place for the insects. Figure 23. — Work of the flat-headed eastern hem- luck bark borer, Melanophila fulvoguttata Harr. A, section of hemlock bark showing larval mines in the inner portion, one-half natural' size ; B, larva ; C, adult, natural size. (Burke) 1'' .Tuniper, or cedar, trees can be felled during August with very little danger of attack if the tops are removed and the poles are laid singly on the ground and turned over once a week for about three weeks to expose a fresh surface to the sun. "Hopkins, A. D. insect injuries to forest tuoducts. U. S. Dept. Agr., Bur. Ent. Circ. 128, 9 p. lUlO. PROTECTION OF LOG CABINS, ETC., FROM INSECTS 17 TREATING WITH CHEMICALS Certain powder-post ^^ and roimdheaded "^ borers can not always be readily controlled by such measures, and to obtain the maximum protection the wood used in the construction of rustic cabins, summer houses, etc., should be treated in the spring, before the first flight of the beetles occurs, with either crude pyridine or coal-tar creosote. These liquids are effective when diluted with kerosene in the pro- portion of one part of pyridine or coal-tar creosote to three parts of kerosene. Methods of applying these liquids are discussed on pages 18 and 19. Whenever it is necessary to cut trees for these purposes during the spring and summer months, while the insects are active, and it is desired to retain the bark on the logs, the logs should be treated, as soon as cut, with one of the chemicals just mentioned. AVhere a slight staining of the wood is objectionable, the same protection can be obtained by carefully removing the bark in sections, applying the solutions to the sapwood, and then replacing the bark, using large- headed nails to fasten the bark in place. One nail to each square foot is usually sufficient for this purpose. Pyridine. — Crude pyridine is a colorless, nearly stainless liquid, and possesses a strong disagreeable odor. Because of this odor, logs or furniture should be treated in the open some distance from any dwelling. If it is necessary to apply this chemical inside a building, the doors and windows should be opened so as to allow ventilation. A windy day would be preferable. Pyridine is inflam- mable, and reasonable care should be taken in handling it, especially where the wood treated is overhead (rafters, etc.), since the liquid dripping down might burn the skin slightly and be especially pain- ful if it came in contact with the eyes. Creosote. — Coal-tar creosote (grade 1, liquid oil) is a dark-brown liquid which stains the bark deeply when applied full strength. When diluted with three parts of kerosene, however, the bark is stained only slightly, and this gives a rather pleasing effect. The odor is not very strong Avhen the creosote is diluted with kerosene. Before it is used it should be strained through burlap, and only a good grade of creosote should be used, the kind recoumiended above ; other- wise the wood mav be stained darker than is desirable. PEELING THE POLES Where it is not especially desirable to retain the bark, a very pleas- ing effect can be obtained by peeling the poles and treating them with creosote and kerosene in the proportions suggested above. The slight stain thus given is just deep enough to give to a cabin a rustic effect which usually is agreeable. The advantage of this method is that the wood can be cut at any time of the year and yet will not be injured by insects. Furthermore, the creosote aids in preserving the wood. In certain localities, peeling the poles and logs is quite 15 Xplobiops basilare. ^^ CalUiliiim aiitfumitum in pino. CaUidium janthinum Lee. in cedar, and Chion cinctut in hickory and oak. 18 FARMERS' BULLETIN 15 82 popular. The peeled poles, however, should be kept off the ground for several days or until they have had a chance partially to season so that they will not be attractive to pinhole borers. Peeled poles thus seasoned will not need treatment with chemicals to protect them from insects. TREATMENT AFTER ATTACK KILLING THE INSECTS WITH CHEMICALS Since it is not always possible to prevent injury by taking the pre- cautions just described and because the greater part of the damage is often done before its discovery, investigations were undertaken to find a substance which will serve as an effective remedy. The results of this investigation proved that both liquid orthodichloro- benzene '' and crystalline paradichlorobenzene are effective. Crude orthodichlorobenzene. — The crude orthodichlorobenzene product is a colorless, stainless liquid and possesses a slight odor. It is noninflannnable, but it is slightly poisonous, and the odor might cause a headache if the liquid were handled for an hour or so at a time. The same precautions should be taken in handling it that are recommended in connection with handling pyridine. It should be applied full strength. Paradichlorobenzene. — Paradichlorobenzene, which has recently proved effective in the control of the peach-tree borer,^'* was found most effective when prepared, as for the preventive treatments, by being dissolved in three parts, by weight, of kerosene. Care should be taken to dissolve all of the crystals. It is noninflammable and only very slightly poisonous. Both of these solutions slowly liberate a gas which kills the insects. This chemical, like orthodichlorobenzene, may destroy the finish on furniture and necessitate revarnishing. If the infested wood is not treated it will eventually be destroyed. SUGGESTIONS FOR APPLYING THE CHEMICALS Wood, before being utilized, can be treated easily and efficiently by being dipped into the solution so that it will penetrate all cracks, crevices, and bark sufficiently to reach the insects and kill them. A trough can be made by bending up the sides and ends of a sheet of some metal, such as galvanized iron, to conform roughly to the shape of the log to be treated. The solution should be poured into the trough and the log immersed. A piece of cord or rope placed under the log will aid in rolling it so that all surfaces will be covered in the course of treatment. After being treated, the wood should be laid in a sunny place to dry. ^' The chemical purchased under this name (also called orthodichlorbenzol) and tested as such against insect attack, as well as most other products on the market to-day which are being sold for this purpose in the place of orthodichlorobenzene, is mainly a liquid which might be called a crude chlorinated benzol product and is not the pure orthodichlo- robenzene. The crude product is manufactured by several concerns, each using its own method, and is being sold under different trade names. It is usually composed largely of monochlorobenzene and ortho-, meta-, and paradichlorobenzene products with the greater part of ortho in it. The pure orthodichlorobenzene is manufactured in limited quantities at the present time and is very expensive ; in fact, too expensive to be used for this purpose. ^^ Blakeslee, E. B. dsb of toxic gases as a possible means of control of the i'E.\cH-TREE boker. U. S. Dept. Agr. Bui. 796, 23 p., illus. 1919. Snapp, O. I., and Alden, C. H. paradichloriibenzexe experiments in the south foe PEACH-BORER CONTROL. U. S. Dept. Agr. Tech. Bui. 58, 40 p., illus. 1928. PROTECTION OF LOG CABINS, ETC., FROM INSECTS 19 Wood in use can be conveniently treated by applying a liberal quantity of one of the foregoing chemicals/'' either with a good spray- ing apparatus or with a brush. To insure the best results it is im- portant to treat thoroughly all parts of the wood. One gallon of the solution of paradichlorobenzene in kerosene or of the crude ortho- dichlorobenzene is sufficient to treat five logs, each 10 feet long and 4 inches in diameter, or approximately 50 square feet of bark sur- face. Two gallons will saturate approximately 100 square feet of wood surface. A pint is usually sufficient to treat a rustic chair of ordinary size. KILLING THE INSECTS WITH HELA.T In the manufacture of rustic furniture it is customary to steam the wood prior to bending it, especially the older pieces of small-dimen- sion hickory. Quite often the material is found to be infested by the previously mentioned types of borers, and it is usually supposed that by leaving the wood in water, through which steam is being passed, for a period of 15 to 30 minutes, the borers will be killed. An examination of material in a factory where the foregoing method was used in the manufacture of rustic furniture from hickory demon- strated that only a very small percentage of the grubs are killed in this short period of time. Results of tests -° have shown that it is necessary to subject infested hickoiy and ash to kiln temperatures of 125° to 130° F. for a mini- mum period of 1^/2 to 2 hours after the wood has been brought up to the initial temperature in order to kill all of the grubs in wood 1 inch thick. Fisher,-^ in verifying the foregoing experiments for the control of Lyctus beetles, determined the period of time necessary for wood of various thicknesses to reach this initial temperature, when infested ash and oak are placed in a cold kiln and raised to the lethal tem- perature of 130° F. In addition to this period a safety factor of one- half hour is added. Following this the wood is subjected to live steam for fi^ to 2 hours in a saturated atmosphere. The schedule is as follows: Thickness of timber Temper- ature required Time re- quired to overcome lag after kiln has attained 130° F. Addi- tional safety factor Time then held at 130° F. Total period in kiln at 130° F. 1 inch °F. 130 130 Hours y% 2 3}i 4>4 Hours ¥2 Hours Hours VA 2 inches 4 2H inches . . 130 130 5K 3 inches 63^ 1^ Pyridine, paradichlorobenzene, and the crude orthodichlorobenzene product are manu- factured by only a few chemical firms. Names and addresses of these firms will be furnished on application to the Bureau of Entomology, IT. s. Department of Agriculture. ™ Craighead, F. C, and Loughburough, W. K. temperatures fatal to larvae of THE RED-HEADED ASH BORER AS APPLICABLE TO COMMERCIAL KILN DRYING. JoUr. Forestry 19 : 250-2.54. 1921. Snyder, T. E.. and St. George, R. A. determination of temperatueeis fatal to THE POWDHR-POST BEETLES, LYCTUS PLANICOLLIS LEI C'ONTE, BY STEAMING INFESTED ASH AND OAK LUMBER IN A KILN. .Jour. Agr. Research 28 : 1033-1038, illus. 1924. ^Fisher, R. C. lyctus powder-post beetles. Dept. Sci. and Indus Res. [England], For. Prod, Res, Bui. 2, 46 p., illus, 1928. ORGANIZATION OF THE UNITED STATES DEPARTMENT OF AGRICULTURE June 21, 1929 Secretary of Agriculture Arthur M. Hyde. Assistant Secretary R. W. Dunlap. Director of Scientific Worh A. F. Woods. Director of Regulatory Work WAi^TEat G. Campbeix. Director of Extension Work, O. W. Warburton. Director of Personnel and Business Admin- VV. W. Stockbehujer. istration. Director of Information M. S. Eisenhower. Solicitor R. W. Wiluams. Weather Bureau Charles F. Marvin, Chief. Bureau of Animal Industry John R. Mohler, Chief. Bureau of Dairy Industry O. E. Reed, Chief. Bureau of Plant Industry William A. Tayi.or, Chief. Forest Service R. Y. Stuart, Chief. Bureau of CJiemistry and Soils H. G. Knight. Chief. Bureau of Entomology C. L. Marlatt, Chief. Bureau of Biological Survey Paul G. Redington, Chief. Bureau of Public Roads Thomas H. MacDonald, Chief. Bureau of Agricultural Economics Nils A. Olsen, Chief. Bureau of Home Economics Louise Stanley, Chief. Plant Quarantine amd Control Administration^ C. L. Marlatt, Chief. Grain Futures Administration J. W. T. Duvel, Clmf. Food, Drug, and Insecticide Administration Walter G. Campbell, Director of Regulat07-y Work, in Charge. Office of Experiment Stations E. W. Allek, Chief. Office of Cooperative Extension Work C. B. Smith, Chief. Library Claribel R. Babj^ett, Librarian. This bulletin is a contribution from Bureau of Entomology C. L. Marlatt, Chief. Division of Forest Insects F. C. Craighead, in Charge. 20 additional copies OF THIS PUBLICATION MAY BE PROCURED FROM THE SUPERINTENDENT OF DOCUMENTS U. S. GOVERNMENT PRINTING OFFICE WASHINGTON, D. C. AT 6 CENTS PER COPY V UNITED STATES DEPARTMENT of AGRICULTURE DEPARTMENT CIRCULAR 411 Washington, D. C. September, 1927 THE RELATION OF INSECTS TO SLASH DISPOSAL Prepared by the Division of Forest Insect Investigations, Bureau of Entomology * CONTENTS Page Slash a factor in forest protection 1 Few species of trees involved 3 Pine slash 4 White pine in the Northeast 4 Red pine and white pine in the Great Lakes region 4 Western white pine in the northern Rocky Mountain region 5 Sugar pine in the Pacific coast region 6 Western yellow pine 6 Jeffrey pine in California 8 Lodgepole pine 8 Page Pine slash— Continued. Monterey pine in California 9 The southern pines 9 Spruce slash 10 Spruce in the Northeast 10 Spruce in the Great Lakes region 10 Engelmann spruce in the Rocky Mountain region 10 Douglas fir slash 10 Conclusions 11 Literature cited 12 SLASH A FACTOR IN FOREST PROTECTION Does slash from cutting operations increase the insect menace to living timber? Many times this question has been asked by foresters and timbermen, but there has been little uniformity in the answers. Considerable confusion has arisen as a result, and a great diversity of opinion is found concerning the influence of slash upon insect out- breaks. Two widely divergent opinions are held by professional forest ento- mologists in North America. In Canada, Swaine (10, p. 18; 11, p. 762; 12, p. 25; 13, p. 4.7; U, p. 231; 15, p. 346^ and Hopping {6, 7) advocate on entomological grounds the necessity of slash disposal as a phase of forest protection. Workers in this country, Graham {2, p. 447), for example, almost unanimously take the opposite viewpoint, that under present economic conditions slash disposal can not be jus- tified on entomological grounds. Chamberhn {1, p. 23), however, 1 This circular was prepared by entomologists and collaborators of the Division of Forest Insect Investi- gations. Those primarily responsible for the information contained in the regional statements are as follows: F. C. Craighead, northeastern and southeastern frrest regions; S. A. Graham, Lake States region; J. C. Evenden, northern Rocky Mountain region; W. D. Edmonston and F. C. Craighead, southern Rocky Mountain region; J. E. iPatterson, north Pacific region; J. M. Miller, H. E. Burke, and H. L. Person, California region. F. P. Keen and F. C. Craighead are largely responsible for assembling the paper as a whole. In making reference to this circulai" it is to be understood that it is a product of joint authorship, as explained in the foregoing. ' Figures in italic in parentheses refer to "Literature cited," p. 12. 31991°— 27 1 2 DErAETMENT CIRCULAR 411, U. S. DEPT. OF AGRICULTURE recommends burning slash of western yellow pine for the control of bark beetles. In England, Munro (S, p. 27), entomologist of the for- estry commission, also recommends burning slash for control of bark beetles. It is fully reahzed, however, that broad statements applying indiscriminately to all forested regions are out of the question; the problem varies with each forest, region, and type. Not only must the species of tree and the character of the slash be considered but the various species of insects that may be involved must be taken into account. It is recognized that, under special conditions, slash disposal or seasonal timing of cutting operations is advantageous. Such cases are referred to in the general text. Hopkins discusses this question in many of his papers. His general conclusions are adequately supported by all the detailed investigations so far conducted by the Division of Forest Insect In- vestigations. As early as 1899 {3, p. 23) he called attention to the wasteful methods of lumbering in the Northwest and the attractive breeding places for forest insects provided by the scarred trunks and the debris left on the ground. Ten years later, in his monograph, (4, P- 25-26, 48), he suggests that the cutting of living timber for commercial purposes may offer favorable conditions for the multiplica- tion of some of the species, although in some cases it may serve as a protection to living timber, and suggests burning the slash after it has attracted beetles away from the living trees. In one of his later papers on forest entomology (5, p. 8) he broadly summarizes his opinions as follows: Since the problem of slash disposal is on the program of this meeting and, since it is pretty generally considered by foresters and some entomologists that slash is an insect hazard to the living timber, I want to say that the results of more than thirts^ years of observations and some detailed study of the problem indicate that as a rule, it is not. As in all rules, there are, of course, exceptions to this one. There are a few cases as related to certain types of forests, time of year, and cases of sporadic cutting, where the slash is dangerous, not so much from the insects that breed in the tops, logs, and stumps, as that it serves to attract the tree-killing insects to the locality and from thus being concentrated they attack and kill the living timber. Continued logging operations, after they are once started within a given area, provide continuous breeding places for the insects and their natural enemies and thus the slash serves as a protection to the living timber. The entomologists of the Division of Forest Insect Investigations feel that a paper setting forth what is now known about the entomo- logical effect of slash would help to clear the situation and stimulate more careful observation and compilation of further and needed data. In this, as in most scientific problems, the last word can never be said, and much investigative work is still needed to clear up many phases of the slash problem. However, considerable work has already been done, and certain tentative conclusions are presented in this circular. There are hundreds of species of insects which breed in the slash of forest trees, but few of these are capable of doing much injury to living trees. They attack the base, the trunk, the tops, the limbs, or the twigs of mature standing trees; others emerge from slash and attack seedlings, saplings, and poles. In addition to this, slash has a very strong attractive influence which may result in bringing thousands of insects into the general , slash area with a resultant varying damage to living timber. THE RELATIOISr OF INSECTS TO SLASH DISPOSAL 3 The direct result of insect attack upon the slash itself is beneiicial because the insects aid in bringing about decomposition. In this circular the direct influence of insects upon twigs, limbs, and tops can be ignored and only the role of slash need be considered in (1) supplying breeding material for insects which emerge and kill mature standing timber or seedlings, saplings, and poles, and (2) attracting insects from the surrounding forest and concentrating them in the vicinity of the slash, where they kill living trees. In general, the insects with which this discussion is concerned breed in the same parts of a fallen tree as of a living tree. Insects which attack the base of standing trees breed in stumps, those attacking the main trunk breed in cull logs, and those attacking limbs and twigs breed in the limbs and twigs composing the smaller portions of slash. There are, however, some important exceptions to this rule, such as certain species of Ips. Probably the heaviest losses of all are attributable to the effect of slash in attracting beetles from the surrounding temtory and con- centrating them in the vicinity, where they are able to do greater damage to the standing timber than if their attacks had been scat- tered over a wider area. This attractive influence has been noted many times. The felling of trap trees ^ has often concentrated attacks on adjacent healthy trees, even in some cases in which the felled trap tree has not been attacked. The beetle population is usually attracted to fire-scorched areas, even though the beetles are often unable to breed successfully in the trees weakened by fire. It is also usually attracted to places where heavy windfalls have occurred or to trees that have been broken down by snow. It is evident that this class of damage can not be minimized through slash disposal. In fact, burning the slash in the summer, which is the flight period of the beetles, may even increase the attractive influence and bring about a still greater concentration. FEW SPECIES OF TREES INVOLVED The problem can be further simphfied by limiting the discussion to such trees as are subject to primary damage from slash-breeding insects. Relatively few trees are thus involved. All hardwoods can be eliminated from the discussion, as practically no insects which breed in hardwood slash are of importance as tree killers. Among the conifers, the slash of fir (Abies), larch (LarLx), redwood (Sequoia), hemlock (Tsuga), cypress (Cupressus, Taxodium), cedar (Thuja, Libocedrus, Chamaecyparis), and juniper (Juniperus) either breeds insects of very little significance as tree killers, or the trees killed are so few or of so little value as to be of small economic importance. As a result of these eliminations the problem in the United States, viewed from an economic standpoint under present forestry practi- ces, resolves itself into a consideration of slash from pine (Pinus), spruce (Picea), and Douglas fir (Pseudotsuga) . Each of these three groups will be taken up in sequence. 'Living trees girdled or felled at the proper time to attract the flying beetles to them and away from healthy trees. 4 DEPARTMENT CIRCULAR 411, U. S, DEPT. OF AGRICULTURE PINE SLASH The pines suffer more than any other group from the attack of bark beetles. It is not surprising, therefore, that pine slash should be viewed with the greatest suspicion as a forest menace. Upon study, however, the danger loses much of its alarming aspect. WHITE PINE IN THE NORTHEAST The only really serious bark -beetle enemy of the white pine {Pinus strohus) which breeds in slash in the Northeast is the Pales weevil {Hy- lobius pales Herbst). Studies by Peirson (9) indicate not only that this beetle breeds in stumps and cull logs but that the adult is also strongly attracted into slash areas for the purpose of feeding. It kills great quantities of small reproduction by gnawing off the bark until girdling results, and is frequently the limiting factor in obtain- ing white-pine regeneration. No satisfactory method of control has yet been devised. Burn- ing the bark of cull logs and thoroughly charring the stumps, or peeling the bark of logs and stumps (both of which are difficult and expensive processes), may lessen the damage to some extent, but will have no effect in lessening the attractive influence of the slash, which is, after all, probably the greatest source of danger. R. T. Fisher, in his experimental silviculture on the Harvard forest, has found that the only practical methods of preventing serious losses are (1) ob- taining such an abundance of reproduction through reproduction cuttings that there are still enough seedlings left to produce a stand after the destruction wrought by the weevil, and (2) clear cutting, and subsequent planting after an interval of three years. RED PINE AND WHITE PINE IN THE GREAT LAKES REGION Graham {2) reports that insect species that normally breed in the slash of the red pine {Pinus resinosa) and white pine (P. strohus) in the Great Lakes region have seldom been observed attacking or kill- ing healthy trees. The insects responsible for the few exceptions to this rule are all found breeding in the stumps and larger parts of the slash. The bark beetle Dendroctonus valens Lee. May occasionally kill trees, and is one of the most common of the species that breed in fresh pine stumps. It is almost never found breeding in parts of the tree more than 6 or 8 feet above the ground. All recorded cases of injury caused by this beetle to a standing tree have been associated with the attractive influence of logging operations, windfalls, fires, or logs in storage. Several species of Ips occasionally kill trees and these, like the Dendroctonus beetles, usually breed most abimdantly in the larger parts of the slash. The most common offenders of this group are Ips pini Say, a primary pest of red and white pines, and /. caUigraplius Germar, which breeds in white pine. In the light of present knowl- edge it is safe to say that in the Lake States only the larger parts of the trees constituting pine slash have any entomological signifi- cance so far as living standing trees are concerned. Just how impor- tant an entomological factor these parts are can not be said, but it is certain that the stumps provide the most favorable breeding places. THE RELATION OF INSECTS TO SLASH DISPOSAL 5 The ordinary method of slash disposal, by burning, destroys only the small, entomologically innocuous parts of the slash, and leaves the parts most favorable for insect breeding. Any method of slash dis- posal that will reduce the number of insects must take care of the larger material. Even burning slash piled over stumps does not as a rule sufficiently char the stump to prevent subsequent insect infesta- tion. Thorough charring can be accomplished only by keeping the fire close to the sides of the stump throughout the process of burning. Thorough charring of stumps is too expensive to be practical. Bark- ing is cheaper, but must be carried down to the mineral soil if satis- factory results are to be expected. Unpublished results of experiments in Minnesota indicate that heavy shade is unfavorable to most potentially injurious insect species. In one experiment, piling the small parts of the slash over the stumps very materially reduced the infestation. This experiment was on a small scale and only about 20 stumps were used, but the results were very clear cut. Pairs of stumps close together were selected; one of each pair was covered wdth the smaller parts of the slash, the other stump being left uncovered. The uncovered stumps were found to contain an average of 40 mother tunnels of Dendroctonus valens per stump, whereas the covered stumps averaged only 4 each. From the data at hand the writers are forced to conclude that slash burning in the Lake States is unnecessary from the entomological point of view. Covering the stumps and larger pieces of the slash with the smaller pieces promises satisfactory results at a minimum cost. WESTERN WHITE PINE IN THE NORTHERN ROCKY MOUNTAIN REGION The most serious insect enemy of the western white pine (Pinus monticola) is the bark beetle Dendroctonus monticolae Hopk. This species breeds successfully in cull logs from logging operations, and also kills living trees. General observations by Evenden indicate that during continuous logging operations the progeny of such beetles as breed in the cull logs are absorbed in the new material made avail- able, so that little damage results to standing trees. Because of the value of this timber species very close utilization is practiced, and ordinarily only a very small quantity of slash over 6 inches in diam- eter is left in the woods. Occasionally, however, where a certain quantity of such material is left in the woods at the close of a logging operation, and no fresh material is provided, the insects which emerge attack and kill standing trees in the vicinity, or seed trees left on the area occupied by the slash. As these beetles do not breed in the smaller tops and limbs the present methods of brush disposal by burning can have no possible eft'ect upon their number. And because of the close utilization of the larger material other measures for preventing injury by insects do not ordinarily appear to be justified. If, however, for any reason, any quantity of large slash material is left in the woods and no fresh material is provided to absorb the emerging broods, then as a pro- tective measure the bark should be peeled from the infested cull logs before the beetles emerge; otherwise some damage to standing trees may result. Two smaller species of insects {Pityogejies carinulatus Lee. and P. knechteli Sw.) breed in the smaller material from the tops. Occa- sionally they breed in sufficient numbers to attack and kill small 6 DEPARTMENT CIRCULAR 411, U. S. DEPT. OF AGRICULTURE white pine reproduction. These cases are of such sporadic occur- rence and of such minor importance that they are negUgible. SUGAR PINE IN THE PACIFIC COAST REGION Tlie bark beetle Dendroctonus monticolae Hopk. is also the principal enemy of the sugar pine (Pinus lamhertiana) in the forests of the Pacific coast. As in white pine, it breeds both in cull logs and in standing trees. This species of pine is not, however, subject to heavy epidemics of infestation such as occur in yellow pine, and no heavy killings have yet been traced to the slash of logging operations. On the Yawkey tract, near Fort Klamath, Oreg., in 1922 and 1923, Patterson, Keen, and Hauge noted a considerable increase in the numbers of standing trees killed shortly after many trees were blown down by a high wind. In general, the considerations applying to utihzation and slash disposal in the case of white pine apply to this species as well. WESTERN YELLOW PINE In California and Oregon the western pine beetle, Dendroctonus hrevicomis Lee, is the principal insect enemy of the western yellow pine (Pinus ponderosa) . Besides attacking living trees this insect breeds in the trunks of fallen trees which are more than 6 inches in diameter. In some cases it has been noted that heavy losses by insects have followed logging operations, whereas in other cases logging areas have been singularly exempt from such injury. Keen reports that on the southern Oregon-northern California project two of the cleanest areas were adjacent to areas where continuous logging had been in progress for several years; that one heavily infested area was adjacent to a logged area where operations had ceased; and that in one unit a reduction of 60 per cent in infestation, equal to the best obtained by artificial control work, followed the beginning of logging operations on adjacent ground. To determine if possible the reason for this condition, Person carried out some investigations in southern Oregon and central Cali- fornia. Eleven logging slash areas, two road slash areas, and one group of windfalls were studied. By bark counts made on 459 pieces of slash it was found that the average number of attacking beetles per square foot was 9.8, and the number of beetles emerging, 16. Similar studies were made by Patterson in southern Oregon. Five logging areas, one windfall area, and 24 miles of road slash were studied; the last named involved the examination of 1,425 pieces of slash, including the examination of 1 square foot of bark on each of 1,075 trees. Bark counts in this material gave 15.6 beetles per square foot attacking and 19 beetles per square foot emerging. Bark counts made on hundreds of standing trees near by showed an average attack of 23 Dendroctonus beetles per square foot, with 54 beetles emerging. It is evident that the attack and emergence on slash material is far below that for standing trees. In all of these studies checks on the surrounding infestation were made before, during, and for several years after the laying down of the slash. Usually the first effect of the slash was to increase the infestation in standing trees in the vicinity. In every case, however, this increase occurred simultaneously with the attack on the slash, instead of follow- ing the emergence of the beetles breeding in the slash. THE RELATION OF INSECTS TO SLASH DISPOSAL. / Numerous observations made by forest entomologists in the West- ern States point conclusively to the fact that the western pine beetle is strongly attracted to the vicinity of slash material, trees scorched by fire, trap trees, and windfalls. As long ago as 1906, Webb (17, p. SO) pointed out that storm-felled and lightning-struck western yellow^ pines became centers of infestation by this insect. If a concentra- tion of the beetles is brought about through the presence of some such material, they not only attack this material but go into the standing living trees in the immediate vicinity. From these investigations the conclusion is reached that the destruc- tion of standing trees by insects, consequent upon logging operations in adjacent territory, is not caused by the breeding up of insects in the slash, but by the concentration in the slash of beetles from the sur- rounding territory, and the failure of the slash to absorb them all. This strong attractive influence can not well be avoided. Since the western pine beetle breeds only in the slash material more than 6 inches in diameter, such as cull logs and butts, the present methods of slash disposal can be of little avail in reducing the numbers of beetles. Neither can the very strong attractive influence of the slash be avoided. The best way, therefore, to avoid injury to neighboring standing trees is to supply continuously a quantity of logs to absorb the broods of beetles, and, if necessary, to reduce, through artificial control, the total population of beetles on the area. Several species of Ips (/. emarginatus Lee, /. oregoni Eich., /. con- fvsus Lee, etc.) breed in the smaller pieces of the slash material as well as in some of the larger pieces. When they become sufliciently numerous, if there is a shortage of slash, they may kill young trees, and the tops and limbs of larger trees. This damage is very sporadic, and usualty follows the interruption of logging operations in the sum- mer months. Keen has reported three small areas on the North War- ner division of the Modoc National Forest, in California, where species of Ips have caused heavy losses of reproduction after the cessation of logging operations in the summer months. The conditions were com- plicated by extremely dry weather. Usually a supply of fresh slash, continuously laid down during the summer months, will absorb all of these beetles and prevent injury to neighboring living trees. In general it may be said that, in the light of present information, no special methods of slash disposal need be recommended to avoid insect damage to western yellow pine, except in the case of sporadic cutting or when logging operations cease. In such cases infested slash material should be destroyed before the broods of insects emerge. The same general considerations apply to western yellow pine in the northern Rocky Mountain region. In the southern Rocky Mountain and Colorado Plateau regions the Black Hills beetle (Dendroctonus ponderosae Hopk.) is the prin- cipal insect enemy of the western yellow pine (Pinus ponderosa var. scopulorum) . Edmonston has reported that in Colorado the forest areas showing least infestation are always those adjacent to places where logging operations are in progress, particularly where the oper- ations have been continuous for several years. Several officials of the Forest Service have reported similar observations. Recent studies by Craighead, Blackman, and Keen in the Kaibab National Forest in Arizona indicate that the felled logs and culls act as traps for the 8 DEPARTMENT CIRCULAR 411, U. S, DEPT, OF AGRICULTURE beetles during the flight period. "When the material is sawn, practi- cally all the beetles are destroyed, and in the logs that are left in the woods during the winter a very high mortality of beetles occurs, so that the emerging beetles are much fewer than those attacking. At the same time the cull logs and tops furnish good breeding material for certain borers (Acanthocinus) and predatory species which are detrimental to the development of the Dendroctonus broods. As these enemies increase with this abundance of breeding material they tend to concentrate on any standing trees which are attacked, and thus hold the infestation at a minimum. Under these conditions it is doubtful whether disposal of the larger slash would not in fact be more injurious than beneficial to neighboring standing timber. In both the Rocky Mountain and the Pacific regions Dendroctonus valens Lee. breeds in stumps and butt logs, and to a limited extent it attacks the base of live trees. This injury is not often severe enough to warrant the expense of special control methods, such as piling brush over stumps, prompt removal of logs, and barking of cull logs. In Arizona, New Mexico, and south of the Colorado Plateau, some outstanding cases of losses to reproduction resulting from insects breeding in slash have been called to our attention. Craighead reports that two species of Ips were found breeding in cull logs and larger tops of western yellow pine on timber sales. The spring generation of beetles is confined to this felled material, whereas the summer generations attack and kill pine reproduction in clumps of from one-tenth to 1 acre. At some places these repeated attacks have materially thinned out the stands of second growth. Modifi- cations of logging operations will be necessary to prevent these losses. JEFFREY PINE IN CALIFORNIA The Jeffrey pine beetle (Dendroctonus jefreyi Hopk.), although often a very destructive insect in living Jeffrey pine (Pinus jejfreyi) in California, is only weakly attracted to the slash of this tree. This species and other bark beetles, such as Ips, breed very freely in wind- falls and large pieces of slash material. On large windfall areas they may occasionally breed up to the point where they become very destructive to adjacent full-grown timber, saplings, poles, and the top of mature trees. Such epidemics are, however, characteristically spo- radic, and their control is not economically feasible at the present time except in cases where high timber values are involved. As far as injury by insects is concerned Jeffrey pine slash is usually of but slight importance. I.ODGEPOLE PINE The mountain pine beetle (Dendroctonus monticolae Hopk.) is a very serious enemy of lodgepole pine (Pinus murrayana), often killing hundreds and even thousands of acres of the standing timber. Here is another case, and a very striking one, of an insect which is strongly attracted to the vicinity of logging or clearing operations, yet rarely attacks the felled trees. Clearings for summer homes or hotels have often brought about such a slaughter of lodgepole pines in the vicinity as to mar the beauty of the site. Even control operations are not immune, and in one instance such a heavy concentration of beetles followed control cutting as entirely to wipe out the effect of the work. THE RELATION OF INSECTS TO SLASH DISPOSAL 9 Nevertheless, a felled tree is rarely attacked. Here, again, it is obvi- ous that slash disposal docs not reduce the number of beetles, and the concentration caused by the slash appears to be unavoidable. Another lodgepole pine i Jisect {Dendroctonus murrayanae Hopk.) has habits similar to those of D. vaJens Lee, discussed under yellow pine. Evenden has found this species of economic importance in crosstie operations in Wyoming. Breeding readily in the stumps, it subse- quently attacks the bases of the larger standing trees not included in the sales. Repeated attacks of this kind weaken the tree to such an extant that it succumbs to the attack of other bark beetles on the bole. MONTEREY PINE IN CALIFORNIA Several serious outbreaks of Ips on the Monterey pine (Pinusradiata) near Monterey, Calif., have been accounted for as caused by wood cut- ting and clearing, where the wood has been left piled in the forest. Other factors, however, enter into this problem, since similar cutting in other j^ears has produced no epidemics. The turpentine beetle (Dendroctonus valens Lee), which breeds usually in stumps, often becomes primary in its attack upon standing trees of this species. Because of the value of the Monterey pine as an ornamental and shade tree, special precautions in slash disposal may well be taken to help minimize insect damage to it, which occasionally becomes serious. THE SOUTHERN PINES The southern pine beetle (Dendroctonus frontalis Zimm.) and three species of Ips (/. calligraplius Germ., /. avulsus Eichh., and I.grandi- collis Eichh.) are the most important pine insects of the South. The first species mentioned rarely attacks anything but living trees, whereas the three species of Ips are more commonly found in tops, cull logs, and stumps than in standing pines. All these species are so intimately associated in the destruction of living trees that it is impossible to consider them separately. On the other hand, the infrequency with which the southern pine beetle attacks slash, cuU logs, or wind-blown trees immediately eliminates it as an argument for the disposal of such material. Very few reports of dying pine timber in the South that can be associated with slash as a factor have been called to the writers' attention, and extensive observations by several entomologists have not revealed any striking examples. In fact, experimental cuttings of timber, conducted throughout the year with the express purpose of furnishing the breeding material for these insects, have utterly failed to produce attacks in the surrounding standing trees. Never- theless, there are many examples which show that these species are all strongly attracted to areas where cutting is being carried on in the summer. If sufficient material is on the ground the}" invariably attack it, and occasionally small quantities of neighboring living tim- ber are killed. For example, a freshly sawn pile of lumber, brought to a home site for building purposes, attracted to that vicinity a suffi- cient number of these insects to kill a number of trees adjacent to the pile. It is therefore reasonable to conclude that slash serving as breeding material for these insects is not a menace, but that because of the attraction which it exerts on them local logging or clearing opera- tions in the summer should be avoided. 10 DEPARTMENT CIRCULAR 411, U, S. DEPT. OF AGRICULTURE SPRUCE SLASH SPRUCE IN THE NORTHEAST Several species of bark beetles breed in the stumps, logs, or tops of spruce (Picea canadensis, P. rubens and P. mariana), and attack and kill living trees. The eastern spruce beetle {Dendrodonus piceaperda Hopk.) is a particularly destructive species which breeds in stumps and cull logs. It has destroyed large areas of mature spruce forests in the past, and active epidemics are now in progress in Canada, even in second- growth stands. Recent observations by Craighead indicate that it is most destructive only when accompanied by one or more species of Ips, which combine with it and attack the upper stems. Several species of Ips (/. horealis Sw., /. perturhatus Eichh., and /. cliagnoni Sw.) have in tw^o cases been observed by Craighead breed- ing in slash, and in the following year attacking and killing near-by living trees. From these, however, scanty broods developed, and in the third year the outbreaks completely died out. Special methods of slash disposal do not appear to be justified from the entomological standpoint, but cull logs and larger debris should not be left in the woods {16, p. 85). The increasingly closer utilization practiced in this region with the development of the pulp industry will undoubtedly tend to minimize such losses. SPRUCE IN THE GREAT LAKES REGION There is no specific evidence to prove that spruce slash in the Lake States has any entomological significance, although there is justification for suspecting that the larger pieces may be of some importance. Most of the spruce {Picea canadensis and P. mariana) cut in this region finds its way to pulp mills, a fact which makes for close utilization. A comparatively small quantity of material suitable for the breeding of potentially injurious insects is left in the woods after logging operations. ENGELMANN SPRUCE IN THE ROCKY MOUNTAIN REGION The Engelmann spruce beetle {Dendrodonus engelmanni Hopk.) breeds in the culls and stumps of the Engelmann spruce {Picea engel- manni) and also attacks and kills living trees. The small quantity of timber of this species which is now being cut makes of small importance the danger from this source. No opportunity has yet presented itself for the study of the efi'ect of extensive logging on this insect. DOUGLAS FIR SLASH There are several insects which breed in the large pieces of slash of Douglas fir {Pseudotsuga taxifolia) and are capable of killing liv- ing trees, though they rarely do so. The more important of these are Dendrodonus pseudotsugae Hopk., Scolytus unispinosus Lee, and Melanopliila druminondi Kirby. In the region along the Pacific coast reports on observations of the death of Douglas fir "from the attack of insects that breed in slash are so infrequent that they can be disregarded. This fact may be due to THE REI^VnON OF INSECTS TO SLASH DISPOSAL 11 the extensive and continuous character of the logging operations. Recently, however, reports from the British Columbia Forest Service indicate heavy killing of Douglas fir adjacent to certain logging operations on the coast of British Columbia. In the northern Rocky Mountain region conditions are somewhat different. The Douglas fir beetle (Dendroctonus pseudotsugae Hopk.) is apparently much more aggressive in these less humid sections. In receat years it has been causing considerable damage, and coming more and more to be considered a serious insect. Evenden believes that several local outbreaks under his observation are clearly attrib- utable to slash which has resulted from logging operations, con- struction of rustic buildings, spruce-budworm defoliation (resulting in the death of many trees), or windfalls. Two small bark beetles, Scolytus unispinosus Lee, and Pseudosy- lesinus nebulosus (Lee.,) occasionally multiply in slash, and when no more material is available they cause damage to reproduction and to young trees. The question of the destruction of Douglas fir by insects needs much more thorough study and more systematic observations before smy conclusions can be ventured. CONCLUSIONS The outstanding conclusions which have been reached to date in regard to the entomological aspect of slash disposal are given here. As far as is now known, pine, spruce, and Douglas fir are the only species of timber to which insects associated with slash are of any important economic significance. Comparatively few species of insects are capable of adapting themselves to breeding in slash and killing living trees. The great majority of the important tree-killing insects which attack slash breed largely in the cull logs and butts. It follows that the present methods of brush burning can have little influence on their control. Where logging operations are continuous, and a constant supply of slash is provided, the potential danger from insects need cause no concern. Slash attracts from the surrounding forests insects which often concentrate in standing timber in the vicinity of the cutting. No method of slash disposal will avoid this effect. In special cases where the value of the surrounding timber is greatly enhanced, either from an sesthetic standpoint as a building site or for scientific purposes such as experimental thinnings in sample plots, extreme caution should be exercised in felling green timber. In such cases the attraction of the felled timber for insects is more important than its service as a breeding ground, and all such work should be done in the fall or winter, at least two months before the growing season. A large number of insects of secondary importance breed in the twigs, limbs, and trunks of fallen trees, and sometimes become so numerous as to kill reproduction, pole stands, and occasionally even mature trees in the vicinity. vSuch outbreaks are, however, sporadic in nature and of short duration, and, under present economic con- ditions, do not warrant special methods of slash disposal. 12 DEPARTMENT CIECULAR 411, U. S. DEPT. OF AGKICULTUEE LITERATURE CITED (1) Chamberlin, W. J 1920. THE WESTERN PINE BARK BEETLE. OrCg. Agr. Expt. Sta. Bul. 172, 30 p., illus. (2) Graham, S. A. 1922. SOME ENTOMOLOGICAL ASPECTS OF THE SLASH DISPOSAL PROBLEM. Jour. Forestry 20: 437-447. (3) Hopkins, A. D. 1899. preliminary report on the insect enemies of FORESTS IN THE northwest. U. S. Dept. Agr., Div. Ent. Bul. (n. s.) 21, 27 p. (4) (5) 1909. practical information on the scolytid beetles of north AMERICAN forests. I. BARKBEETLES OF THE GENUS DEN- DROCTONus. U. S. Dept. Agr., Bur. Ent. Bul. 83, pt. 1, 169 p., illus. 1922. budworm INFESTATION VS. PULPwooD PRODUCTION. Amer. Paper and Pulp Assoc, Woodlands Sect. Proc. 2: 7-8. (6) Hopping, R. 1915. THE entomological aspect of SLASH DISPOSAL. Soc. Amer. Foresters Proc. 10: 183-185. (7) 1921. THE CONTROL OF BARK-BEETLE OUTBREAKS IN BRITISH COLUMBIA. . Canada Dept. Agr. Ent. Branch Circ. 15, 15 p., illus. (8) MUNRO, J. W. [1920]. SURVEY OF FOREST INSECT CONDITIONS IN THE BRITISH ISLES, 1919. [Gt. Brit.] Forestry Comn. Bul. 2, 35 p., iUus. (9) Peirson, H. B. 1921. THE LIFE HISTORY AND CONTROL OF THE PALES WEEVIL (hYLOBIUS pales). Harvard Forest Bul. 3, 33 p., illus. (10) Swaine, J. M. 1914. FOREST INSECT CONDITIONS IN BRITISH COLUMBIA. Canada Expt. Farms, Div. Ent. Bul. 7, 43 p., illus. (11) (12) (13) (14) (15) 1917. SHADE TREE AND FOREST INSECTS IN MANITOBA. Agr. Gaz. Can- ada 4: 755-763. 1918. CANADIAN BARK-BEETLES. PART II. Canada Dept. Agr. Ent. Branch Bul. 14, 143 p., illus. 1919. SOME INSECT INJURIES IN WOODLOT8. Quebec Soc. Protect. Plants Ann. Rpt. (1918/19) 11: 46-48, iUus. 1919. THE BALSAM INJURY IN QUEBEC AND ITS CONTROL. Agr. Gaz. Canada 6: 227-233, illus. 1921. SPRUCE BUDWORM INJURIES IN EASTERN CANADA. IllUS. Canad. Forestry Mag. 17: 345-346, illus. (16) Craighead, F. C, and Bailey, I. W. 1924. STUDIES ON the SPRUCE BUDWORM [CACOECIA FUMIFERANA CLEM.] Canada Dept. Agr. Bul. (n. s.) 37, 91 p., illus. (17) Webb, J. L. 1906. SOME INSECTS INJURIOUS TO FORESTS. II. THE WESTERN PINE- DESTROYING barkbeetle. U. S. Dept. Agr., Bur. Ent. Bul. 58, pt. 2, p. 17-30, illus. additional copies OF THIS PUBLICATION MAY BE PROCURED FBOU THE SUPERINTENDENT OF DOCUMENTS GOVERNMENT FEINTING OFFICE WASHINGTON, D. C. AT 6 CENTS PER COPY V U. S. DEPARTMENT OF AGRICULTURE FARMERS' BULLETIN No. 1472 PREVENTING DAMAGE BY TERMITES OR WHITE ANTS THROUGHOUT the United States native termites, or white ants, cause serious damage to the foun- dations and woodwork of buildings and articles in the buildings, as well as to living fruit and other trees, crops, and other vegetation. Such damage can be prevented by the proper construction of buildings and by chemical treatments of wood, and injury to growing vegetation by clean culture and the use of insecticides. This bulletin describes the habits and activities of subterranean and nonsubterranean ter- mites and sets forth in detail the precautions to be taken against them and the remedies available for damage which they have inflicted. This bulletin supersedes Farmers' Bulletin 1037, White Ants as Pests in the United States and Methods of Preventing Their Damage. Washington, D. C. Issued April, 1926; revised June, 1930 II PREVENTING DAMAGE BY TERMITES OR WHITE ANTS By T. E. Snydesr, Senior Entomologist, Division of Forest Insects, Bureau of Entomoloyy CONTENTS Page 1 Termites and their habits Distribution and forms Location of colonies or nests Termites which are subterranean in habit Termites which are nonsubterranean in habit The colonizing' swarm The reproductive forms Preventing and remedying damage to woodwork of buildings Destruction of breeding places about the building site Proper construction of buildings Modifications of city building codes. Locating and temporarily arresting the damage 15 Indications of infestation 16 Page Preventing and remedying damage to woodwork of buildings — Contd. Killing the winged adults will not stop the damage 16 Disconnecting wood from the ground 17 Replacing with concrete 17 Replacing with metal ' 17 Spraying and poisoning 17 Preventing and remedying injury to living vegetation 18 Fruit, nut, shade, and forest trees 18 Young plantations or nursery stock- 18 Vineyards 19 Field and truck crops 19 Flowers and greenhouse stock 20 Summary 21 TERMITES AND THEIR HABITS DISTRIBUTION AND FORMS T ERMITES, or '' white ants." are destructive native insects of which 44 species occur in the United States. They are dis- tributed throughout the country, although in the southern, south- western, and Pacific coast regions, where both the subterranean and nonsubterranean kinds occur (fig. 1), they are more numerous and injurious than elsewhere. These so-called white ants are not true ants, although they are superficially antlike and live in colonies made up of different forms or castes. In these nests or colonies both wingless and winged ma- ture individuals are produced. The brownish or blackish, elongate, slender, antlike, colonizing, sexual adults (fig. 2) with long white wings, unlike the other forms, have functional eyes and their bodies are able to endure full sunlight. These migratory males and females appear normally once a year during a short period. There are three stages in the life of white ants : The egg, the immature form (nymph), and the mature individual (including sterile workers (fig. 12, 6), soldiers (fig. 12, «), and the various fertile reproductive forms) . Farmers' Bulletin 1V72 LOCATION OF COLONIES OR NESTS The nests of some species of termites ^ are in the earth and in dead and decaying wood. These species are of subterranean habit, timber and trees being attacked by the workers only through the ground. The nests of some other species,^ however, are excavated in wood and trees by the winged forms, there being no workers and no under- ground hfe. With the clearing of land and the consequent destruction of their natural breeding places in the dead trees, decaying stumps, and logs of the forests, termites become increasingly destructive to the woodwork and contents of buildings (figs. 3-9), telephone poles, fences, or any timber in contact with the ground, as well as to living vegetation, including not only fruit and shade trees, shrubs, and flowers, but also truck (fig. 10) and field crops and, in California, Fig. 1. — Map showing Cline AA) the northern limit of damage by subterranean termites in the United States; BB, the northern limit of damage by dry-wood or nonsubterranean termites grapevines. The principal food of termites is cellulose, which they obtain from either dead or hving vegetation. Termites in the United States are mainly species of subterranean or wood-boring habit and are not so spectacular or common as the mound-making or tree-nesting termites of the Tropics. Very few termites in this country have habits which make them conspicuous, or come above ground into the sunlight, except during the annual colonizing swarm; hence they largely escape notice until they become injurious. TERMITES WHICH ARE SUBTERRANEAN IN HABIT Subterranean termites live in forests, building their nests in the wood of standing timber, logs, or stumps, in cleared land, any wood 1 Genera Reticulitermes Holmgren, Leucotermes Silvestri, Amitermes Silvestri, etc. 2 Genera Termopsis Ueer, Kalotermes Ilagen, Neotermes Holmgren, Cryptotermes Banks, etc, Preventing Damage by Termites or Wliite Ants in contact with the ground or, in the plains, in a labyrinth of underground passages in the earth, usually underneath wood or vegetation. Termites are soft-bodied and always conceal themselves within wood, in the earth, or within their earthlike carton shelter tubes (fig. 11). The grayish-white, soft-bodied, wingless, sterile "workers" (fig. 12, below) are in reality the destructive form. These workers make the excavations occupied by the colony and enlarge and extend them as the colony increases. They live underground or within the wood, are blind, and shun the light; as a result they are rarely seen. In burro ^^'ing through wood the workers often com- pletely honeycomb it, usually following the grain and eating out the softer, thin-walled, larger-celled spring or new wood. They are able to penetrate the hardest of woods, pro- vided they have access t o moisture in the ground . In extending their gal- leries in wood and vege- tation, subterranean spe- cies carr}" moisture with them by means of moist excrement mixed \\iih. earth. TERMITES WHICH ARE NONSTJBTERKANEAN IN HABIT The nonsubterrancan termites which are injuri- ous attack wood directly; but, instead of follo^^■ing the grain continuously, they excavate through it longitudinal chambers of limited length. The sex- ual adults, after they have lost their ^\'ings, and the young or m^mphs, are the destructive forms. Their pellets of excrement (fig. 13) are regularly impressed, and sometimes completely fill or block up the burrows in a compact ^mass; thej^ are often expelled as dry droppings from the infested wood. These termites are destructive to the woodwork and furniture in build- ings (figs. 14, 15), as well as to living trees. Apparently they can exist without the great amount of moisture necessary to the life of termites which are subterranean in habit. Fig. 2. — Winged sexual adults of eastern subterranean termites; upper, Reiiculitermes tnrginicus, nearly 3ii times natural size; lower, R. flavipes, enlarged 3 times THE COLONIZING SWARM At certain seasons, usually spring or fall, but varying with the species and the locality, the winged, sexual individuals migrate in large numbers from the parent nests. They then lose their wings and breed new colonies. In the case of the subterranean termites, wood and trees are usually entered indirectly through the ground, Farmers' Bulletin U72 although sometimes these insects enter trees under bark loosened by sunburn, etc., or through scars or borer holes, provided sufficient moisture is present. Nonsubterranean termites enter the wood directly, or, in the case of trees, through wounds or borer holes or under loose bark; moisture is not neces- sary. In the new quarters eggs are laid, the young develop, and in a few years the colony increases in numbers, and the " workers " are able to feed and care for the repro- ductive forms — the " king " (title page, left) and "queen" (title page, right) — as well as the soldiers (fig. 12, a), Avhich are sterile forms adapted to protect the colony from insect enemies, notably the true ants. In recently formed young colonies the rate of egg laying is slow, but mating is repeated, and, al- though there is at first a gradual increase, later the increase in the numbers of the broods is rapid. In old colonies there are thousands and tens of thousands of indi- viduals. Egg lajdng occurs over a considerable ]:)eriod during the warm months in col- onies out of doors. .„ . In infested buildings artihcially heated, where an even temperature is maintained, the insects are active and may lay eggs every month of the year. The number of eggs laid depends on age. Fig 3. — Damage to oak flooring hv tlic ((ininion vastcvn subterranean termite Reticulitermes flavipes. Note that damage is not apparent on upper surface Preventing Damage by Termites or White Ants 5 THE HEPEODTJCTIVE FORMS Owing to the increasing number of eggs that develop within her, the queen becomes enlarged, but never loses the power of locomotion. It was once believed that, since the queen mother was the source of the colony life, the termite colony would be exterminated if she were destroA'ed, but this has been disproved by more recent studies. In addition to the forms that have shed their wings, several different tvpes of reproductive forms occur — forms with wing pads (the un- developed wings of the nymphs) and wingless reproductive adults. The winged forms, however, are the normal type and occur as a single pair, whereas there may be hundreds of the other forms head- ing colonies. The reproductive forms with wing pads and the wholly wingless type usually have little color to the body, and the eyes are small. These forms rarely come above ground or leave the burrows in wood. Fig. 4. — Quartpi-ed-onk flooring damaged by the suliterranean termite_ iee^cMii- tcrincs fluripes in an infested Iniilding-, Wasliington, D. C, IJlo The location of the queens in the colony depends upon the seas(m of the year. During periods of intense heat or drought in the plams or in arid or prairie regions the subterranean termites burrow deeply below ground or to a less depth under stones, cow chips, etc. During winter in the colder climates they burrow below the frost line. Whole colonies of subterranean termites migrate when conditions become unfavorable. The nonsubterranean termites, on the other hand, are not able to leave the wood in which they have excavated their nests. Farmers' Bulletin U72 PREVENTING AND REMEDYING DAMAGE TO WOODWORK OF BUILDINGS DESTRUCTION OF BREEDING PLACES ABOUT THE BUILDING SITE Fig. 5. — Tube of coarse yarn from l)ali' of eottim on floor of building infested by subterranean termites, Green- ville, S. C. If buildings are to be constructed on recently cleared woodland, decaying logs and stumps should be removed from the soil in the vicinity and burned. If, because of the presence of decaying wood and humus, the sub- terranean termites are numerous in the earth, the soil should be deeply p 1 o av e d or otherwise broken up and t r e a t e d with chemicals to kill the insects. Effective poisons for this purpose are sodium cyanide ; ^ a 10 per cent solution of sodium arsenite;'^ kerosene oil; 1 part coal - tar creosote and 3 parts kero- sene oil (this mixture should be strained through burlap before use) ; carbon-disulphide emulsion, w^hich is on the market ready for use ; orthodichlorobenzene ; lye ; or other contact poisons or gases. Live steam forced into the soil will serve the same purpose as the gases. Decaying fence posts, sidewalks, etc., should be removed and re- placed with treated wood, concrete, stone, or other resistant substances ; such de- caying material w^ould facilitate the formation or perpetu- ation of the termite colonies. PROPER CONSTRUCTION OF BUILDINGS Termites will in- fest not only old buildings but also im- properly constructed new buildings, and these are often badly infested. It is not the age of the building but the manner in which it has been constructed that renders it liable to attack. Insulation. — Complete insulation from the ground of all untreated woodwork of buildings is the only effective permanent remedy 3 For each acre to be treated, dissolve ICO pounds of granular sodium cyanide in 12,000 gallons of water. " This poison is caustic and should not be used near living vegetation. Fio. G. — Cotton jacket of rubber-lined fire hose from in- fested building in Missouri, damaged by subterranean termites (Rcticulitermcs sp.) Preventing Damage by Termites or White Ants Fig. 7. — Revenue stamps damaged by the subterranean termite Rcticulitcnnes ftavipes on infested flooring in tlie Bureau of Engraving and Printing, ^Yaslnngton, D; C, 1921 ) COUNTY B ISSUES >/ ROAO IMPROVEXIENIB^ ) -•o4>^ ( h / is; Fig. 8. — Correspondence and advertisement regarding issue of county bonds ; dam- aged by subterranean termites infesting the building lu Virginia in which they were stored 113247'— 30 2 8 Farmers' Bulletin 1^72 against attack by subterranean termites, and the onl}' relief from their presence. These insects must maintain contact with the ground to obtain the moisture necessary for their existence. When contact with their moisture supply in the earth is cut off, the subterra- nean insects in the damaged Avood, no matter how numerous, soon dry up and die. Foundations, supports, etc. — To prevent subterranean termites fi'om reaching the woodwork of buildings from their nests in the ground, the foundations of buildings should be constructed, if possible, entirely of stone, brick, concrete, or concrete and steel,* including the pillars in the basement or cellar. The Avails, partitions, and flooring in the ground floor, basement, or cellar should also be of con- crete. Wooden floor- ing can be laid over this concrete floor if desired. If the floor- ing is to be of con- crete, the concrete should be laid on a gravel base. In buildings where stone, brick, or con- crete foundations are impracticable, timber impregnated with coal-tar creosote should be employed, and no imtreated wood should come in contact with ground which may be infested with termites. Wood to be protected from termites should be im- pregnated with coal-tar creosote by either the cylinder-pressure or the " open-tank " process. Full details regarding these processes can be obtained from the United States Forest Products Laborator}^, Madison, Wis. The open-tank process is simpler, can be made to give satisfactory results where pi'operly used, and can be operated by unskilled labor. If for any reason neither of the foregoing processes can be used, three coats of hot coal- tar creosote brushed on the wood, with sufficient intervals betAveen brushings to permit each coat to dry, Avill be fairly effective. This Fig. 9. — Damage by the sul> terranean termite Rcticuli- termcs fiar.lpcfi to shoe stored on infested wood- work in a building in New York Cltv Fig. ]0. — In.inry to onrrots by the sui)terr;inean ter- mite Rcih-nUlvvutcs clari- pcnnis, at Dallas, Tex. * In the Southern States, especially in the subtropics, the more valuabh buildings should be constructed entirely of steel and concrete. permanent Preventing Damage by Termites or White Ants 9 method, liowevcr, is not generally recommended, since it will preserve the wood for onl}^ a few years. The supports of porches or steps should never be laid directly on the o-round, but should rest on rock or concrete. WindoAv sills and frames in the basement or cellar should be laid over concrete and the woodwork should not come in contact with the ground. The supports of the woodwork of coal bins in basements or cellars should not be set in the ground, but should rest on concrete, not extending through the concrete into the soil. Concrete flooring. — Even in permanent stone or concrete and steel buildings the concrete flooring is often constructed improperly. Fill. 11 1 .niMii. oarthlike, shelter tubes constructed by the eastern ijpiJlliUiiLllliean termite I'rtieiiUitermes flavipes over brick wall in dark, heated, damp Ibasemient ; these tubes are used in passing over impenetrable substances. Inset, near view of tubes to show texture Usually the base of the concrete floor is a loose combination of coarse gravel or cinders and cement grout. This very rough con- glomerate, even if several inches thick, has many cracks and large holes running through it. Over this is laid a layer of solid concrete about 2 or 3 inches thick, of fine texture, in Avhich untreated wooden sleepers are laid while it is still moist. These sleepers nearly or quite reach the coarse, open conglomerate in contact with the earth, and to them is nailed the wooden flooring. (Fig. 17, A.) It will be seen that this is faulty construction. Termites have free access from the earth, in which they have galleries, through the porous conglomerate, to the untreated beams and flooring. There should be a layer of solid concrete at least 1 inch thick betiveen the grout and the icood. (Fig. IT, B.) 10 Farmers' Bulletin i^72 Among the commonest means of infestation are wooden sleepers or stringers laid in concrete while the latter is still soft, or placed before the concrete has been poured in. Ter- mites enter through these wooden beams. Other common means of infestation are sup- ports of coal bins ex- tending through con- crete and through the disintegrated lime mor- tar of brick walls. Termite shields, guards, or metal caps. — The most injurious termites m this country are subter- ranean in habit and re- quire constant access to the earth in order to attack wood which is either in contact with the earth or which they reach through cov- ered, earthlike shelter tubes constructed over the face of stone, con- crete, or brick founda- tions. In consequence they can be kept out of buildings by means of metal barriers. By Fig. 12. — Mature soldiors («) and mature worker.s (h) of the eastern subterranean termite Reticiiliterrncs fiavipas. Sligbtly more than six times natural size simply inserting a sheet of noncorroding metal to serve as a mechanical bar- rier or " termite shield " into the masonry and turning the projecting edges downward at an angle, communication of termites with the earth, where they obtain mois- ture, can be cut off. In less pretentious frame build- ings, metal caps are placed over the tops of construc- tion stone piling or pil- lars, or wooden supports. This is a similar method to that used in rat-proof- ing corn cribs. It is effec- tive and practicable where untreated timber is placed over masonry foundations. Fig. 13. — Impressed pellets of excrement of non- subterranean termites (Kalotermes sp.), which drop from infested wood. Greatly enlarged Preventing Damage hij Termites or White Ants 11 Again, in the case of stone and steel buildings, the steel or stone pillars or piping extending down through the concrete floor to foun- dations in the earth often make infestation possible, OAving to the fact that the concrete floor does not fit tightly about them. Over- lapping strips of metal extending horizontally several inches from the pillars or pipes should be imbedded in the concrete floor in order to obtain a tight joint (flg. 17, B) ; or liquid (adhesive) asphalt should be poured in to plug up the crevice or frame. ^ .^:,fm^,^:..,.,V9^ Fig. 14. — Bottom of bureau drawer daiiiaged by the uonsubterranean wood-boring' termite Cryptotcrmes hrcvis, which occurs at Key West, Miami, and Palm Beach, Fla. Avoiding" dampness. — Complete dryness of foundation timbers and basement walls and flooring is an important aid in rendering build- ings safe from attack by termites. Dampness, warmth, and dark- ness attract these insects. A deep air space should be left between the ground and wooden flooring, unless, as in factories, heavy truck- ing is to be used over the floor, in which case this is impracticable. An air space should be left between the concrete floor and the wooden floor laid over it. Concrete floors should be laid on a gravel 12 Farmers' Bulletin U72 base, which will prevent dampness and cracking. The points of juncture between concrete walls and wooden flooring should be filled in by rounding off the concrete at these places, since cracks often occur Avhere the wall and floor join at right angles. (Fig. 17, Fig. 15. — Funiiture damaged by the nonsubtcrranean, wood-boring termite Crypto- tcrmes hrevis. Key West, Fla. B.) Termites often come up through cracks between walls and flooring. By mixing a heavy mineral residual oil with Portland cement, a material is formed almost perfectly nonabsorbent of water and therefore excellent for use in damp-proof construction. Where the Preventing Damage by Termites or White Ants 13 various patent or noiseless floorings are used on the ground floor they should always be laid oyer a concrete base, especially if they contain wood fiber as a constituent. In no case should untreated beams be completely surrounded with mortar or brick; there should be a space around them sufficient to permit air circulation. Beams should not be set in earth or in moist concrete, but on rock or dry concrete, or in grooves in the latter. Bungalows or frame buildings which have no cellar should be raised from the ground on stone, concrete, or brick foundations to a height whicli will allow light and air to penetrate beneath. Lime mortar. — In brick walls, where lime mortar is used, this some- times disintegrates after a few years and termites penetrate through the spaces thus left between the bricks, especially where the brick- work is below the ground level. (Fig. 16.) Such walls should be faced with Portland cement 1 inch thick, especially if untreated wood is to come in contact with the bricks. Fici. 16. — Interior view of portion of wliitewaslied In-ick foniulation wall of builil- ins, bolow srounrt level, showing! sliplter tubes of onr common subterranean termite (ReticuUtermrs sp.) penetratiuR the disintegrated lime mortar. These termites cam(^ through the earth banked up against the exterior wall. To remedy this condition the exterior wall will have to be faced with concrete for some distance below the ground level Use of chemically treated wood for interior woodwork, furniture, etc. — In the Southern States, especially in the subtropics, in the more A'aluable permanent buildings the interior woodwork, furniture, etc., should be impregnated with preservatives, since nonsubterranean termites that attack wood directly are common in those regions. Zinc chloride, bichloride of mercury,^ sodium fluoride, and chlori- nated naphthalene*^ are effective preservatives. ^ The extremely poisonous character of mercuric chloride renders its use dangerous. It is slowly volatile, and there is a possibility that it will be given off continuously in small quantities from the treated wood. However, it has been extensively used in Germany and apparently without serious consequences. '■' This preservative is usually referred to as tricblornaphthalene and, as compared with other chemicals, it is reallv comparable to a technical product having naphthalene, mono- chloronaphthalene, dichlor'naphthalene. and probably some of the higher chlorinations as impurities. Its melting point ranges between 190 and 210° V. — the specification under which it is sold. 14 Farmers' Bulletin U72 Wood-pulp products, such as the various wood-fiber processed or composition boards, for interior finish and substitutes for latli (fig. 18), or for exterior use, can be protected from attacl^ by termites by adding certain poisons, such as crude carbolic acid, to the i^ulp or laminated boards in the course of manufacture. Available poisons Fig. 17. — A, Impioperly constnicted concrete flooring : a, Gravel or cinders loosely cemented with coarse concrete, 3 inches thick, but with many crevices and holes ; b, .'folid, den,se concrete, '2 inches thick : r, 2 by 4 inch untreated wood sleeper set in moist concrete over the srout ; d, %-inch pine flooring nailed to sleepers. U, Prop- erly constructed concrete flooring : a, Gravel or cinders loosely cemented with coarse concrete, but with many crevices and holes; h. asphalt waterproofing 14 inch thick; c, dense concrete. '1 inches thick ; (f^ 2 by 4 inch treated wood sleeper .set in a groove in concrete which insulates it from termites in the earth ; r-, %-inch flooring nailed on sleepers; f, metal collar around pipe which runs down through the concrete (this collar should be soldered to the pipe and embedded in the concrete) ; ff, shoulder of concrete at point of wall and concrete floor to avoid a right-angle connection and consequent cracking for this purpose are crude carbolic acid at the rate of 1 gallon to 1,000 square feet; bichloride of mercury at the rate of 49 ounces per 1,000 square feet; or copper sulphate at the rate of 113 ounces per 1,000 square feet. Chlorinated naphthalene is a suitable poison for cane-fiber boards. Preventing Damage by Termites or White Ants 15 MODIFICATIONS OF CITY BUILDING CODES One of the simplest and most effective means of prevention of at- tack would be to modify the building regulations or codes of various cities so as to include a few simple rules to protect houses from dam- age by termites. As the principal object in view is to keep all un- treated wood from contact with the ground, where the termites live and from which they get their moisture, the regula- tions should stipulate that no floors, sills, beams, clapboard, etc., of untreated wood may be laid on or in the earth and that untreated beams may not be laid in con- crete without at least 1 inch of concrete underneath and sep- arating it from the earth; that in founda- tions or in cellar walls in contact with the earth a special grade of hard mortar should be used, since lime mortar^ after some years' service disinte- grates; that all brick- work extending below the surface of the ground shall be faced and capped w^th con- crete at least 1 inch thick; and, where nonsubterranean as well as subterranean termites occur, that only woodwork impregnated with preservatives be used for exterior and interior construction, unless it is impracticable to obtain such treated wood. LOCATING AND TEMPORARILY ARRESTING THE DAMAGE Although it may be difficult to eliminate termites and stop further damage by them, when once these insects have become established in the woodwork of a building, the approximate point of entrance should be sought at once by careful examination of all woodwork in contact ' The Bureau of Standards of the United States Department of Commerce recommends a mortar composed of 1 part Portlarid cement to 3 parts of sand graded from fine to coarse, with no grains hirger than will pass through the No. 10 sieve, to which may be added 10 per cent by weight of tlie cement of some workability agent, such as hydrated lime, for use in locations wheif^ termites abound. Such a mortar, it is believed, will have the desirable properties of both cement and lime mortars and, furthermore, will contain a suflScient quantity of cement to prevent the penetration of it by the termites. (See fig. 16.) Fig. 18. — I'ressed wood-pulp tile mined by subterranean termites infesting the building, Biloxi, Miss. 16 Farmers' Bulletin U7^ with the ground. To do this, it may be necessary to tear 1143 the foundations, flooring, and some other woodwork. The foundation timbers and interior woodwork found damaged shoukl be removed, and the ground where they were set should be broken up and drenched with some liquid which will kill or at least temporarily pre- vent the furtlier activity of termites at that point. Any of the in- secticides ^ mentioned under the heading " Destruction of breeding places about the building site " (p. 6) will meet the need. INDICATIONS OF INFESTATION The annual emergence of large num- bers of the flj'^ing termites is an indica- tion as well as a warning that the wood- work is infested, and tlie point of emer- gence indicates the approximate location of the infested timbers. Even if the in- sects are not observed '' swarming," large numbers of the dead winged adults or of the discarded wings usually will be found near by. Frass and earth thrown out of crevices through which the insects emerge are also evidences of their presence. Another Avarning is the presence of branching shelter tubes of small diameter, made of earth mixed with finely powdered wood, on founda- tion timbers or other woodwork, or over the stirface of stone, brick, or other im- penetrable foundation material (fig. 11), through which the insects travel from the grotmd to the woodwork. These tubes should be broken off and the groimd where they originate broken up and drenched with one of the liqitids named in the paragraph under the head- ing, "Destruction of breeding places about the building site " (p. 6). In the case of the nonsubterranean termites, which infest wood directly, evidences that they are damag- ing wood are the impressed pellets of excrement (fig. 13) Avhich are expelled from the wood. Other evidences are the holes, similar in size to BB shot, where the insects entered the wood. (Fig. 19.) Ficj. 10. — Entrance holes of sex- ual, colonizing adults of a non- subterranean termite {Kalo- tenncs hnbhardi) in wood of dead cottonwood tree in Ari- zona KILLING THE WINGED ADULTS WILL NOT STOP THE DAMAGE When efforts are made to prevent fttrther damage by termites in buildings, it slioidd be realized that the numbers of these insects may be constantly recruited from some undiscovered, outside, central colon}'. The destruction of the winged colonizing adults with house- * If sodium cyanide is used, a strong solution, 1 ounce to a gallon of water, is desirable. Preventing Damage by Termites or White Ants 17 hold ammonia, etc., at the time of emergence, although beneficial in preventing the establishment of new colonies, will not eradicate the insects infesting the woodwork. The most destructive forms are the white, wingless workers, which remain within the wood. DISCONNECTING WOOD FROM THE GROUND Subterranean termites infesting beams or other wood will die out if the wood is disconnected from the ground. Knowdedge of this fact will save time and expense, especially in the case of old frame build- ings, where extensive repairs would be unwarranted. Disconnecting untreated foundation timbers from contact with the soil will also cause the death of subterranean termites in the other woodwork, furniture, and stored material in the building, even if they have penetrated to the second or third floors. These timbers need not be removed or replaced unless seriously weakened structurally. How- ever, if tlie wood is kept moist by some other means, such as water leakage, the termites will continue to work and thrive. This applies especially to damp corners of basements near outside water pipes, bathrooms, kitchens, and the like. Wooden floors laid directly on the ground or on stringers on the ground, or set in concrete, should be removed. There should be a layer of concrete between the earth and the wooden floor (fig. 17, B). Wooden baseboards should be removed. REPLACING WITH CONCRETE Concrete floors and concrete baseboards should be substituted for wood. Untreated beams penetrating through concrete floors into the earth and the lower parts of door jambs and casings should be cut off at least 6 inches above the ground or floor and replaced with ce- ment plinths, which should project one-quarter inch beyond the jambs and casings. Metal strips should be sunk down from the w^oodwork into the concrete. Wooden thresholds, wainscoting, window sills, subsills, and stools in the basement or ground floor should be removed and placed on concrete (a layer of concrete between the earth and wood) or replaced with concrete. REPLACING WITH METAL In basements and cellars steel rails or other structural metal work can sometimes be economically used to replace weakened timbers. SPRAYING AND POISONING Fumigation, poisons, and spraying are of no permanent value against subterranean termites in buildings, since, while they may kill the flying insects and some of those in the wood, others will continue to come up from the ground. In the case of termites which do not live in the ground, however, but attack wood directly, it is advisable to remove and replace the wood if the damage is slight and localized. Where the wood has been seriously damaged, but not structurally weakened, saturate the infested wood with orthodichlorobenzene. The wood should be thoroughly saturated with this chemical, a rag or mop being used, 18 Farmers' Bulletin iV72 dripping wet, or the liquid can be applied as a spray. Several appli- cations may be necessary to kill the insects. If orthodichlorobenzene is used as a spray, it is advised that the house be opened up before and for some time after treatment, since there is quite an odor to the chemical which may prove disagreeable in a closed room. Also, in spraying timbers overhead care should be taken not to let the liquid drip down, since it might slightly burn the face and hands and w^ould be painful if it got into the eyes. If the orthodichlorobenzene treatment is not practicable and the wood is too thick for the solution to penetrate, blow dry Paris green by means of a bellows into holes bored with an auger into the infested Avood; these holes should penetrate to the galleries of the termites. If, because of moisture, the Paris green becomes caked, the treatment should be repeated. Wood structurally weakened should be removed and replaced with treated wood, discussed in Department Bulletin 1231, or strengthened with structural steel. By far the greater and more serious damage to timber in the United States is caused by termites of the subterranean type. De- partment of Agriculture Leaflet 31, on the prevention of damage by termites in buildings, discusses in detail the control of subterranean termites. PREVENTING AND REMEDYING INJURY TO LIVING VEGETATION FRUIT, NUT, SHADE, AND FOREST TREES Termites cause occasional but serious injury to living trees, shrubs, nursery stock, and grapevines. A wise preventive measure is the removal of all loose wood which may afford them shelter, such as prunings, dead and dying trees and the like, and untreated fence posts and similar material. Cleanliness in orchard and forest man- agement is important. Since termites render unmerchantable the forest trees which have been killed by insects, fire, or disease, all timber from such trees should be utilized or removed as promptly as possible. Covering scars and pruned areas. — To prevent infestation, care should be taken that the trees do not become scarred, especially near the base. Scars and all pruned areas should be treated Avith a mix- ture of one-fourth creosote and three-fourths coal tar. This mix- ture should not be allowed to come in contact with the living tissues at the edges of the bark ; to protect them a shellac should be applied. Commercial fertilizers. — Soil heavily manured will attract subter- ranean termites, since they can obtain food from the animal manure ; commercial fertilizers should be used in preference in regions where termites are common in the soil. YOUNG PLANTATIONS OR NURSERY STOCK Injury to nursery stock will be more serious on recently cleared land, to stock from 1 to 3 years old, and where decaying wood is abundant. Any debris in which the insects breed should be removed. In general the use of recently cleared land should be avoided in planting nursery stock. Earth used in banking should be free from rotten wood. Care should be taken not to allow the roots to dry out before planting, as weakened stock is specially susceptible to attack; particular care should be given grafted stock. In the case Preventing Damage by Termites or White Ants 19 of the pecan it is recommended that two or three cereal crops be grown on newly cleared land before the young trees are set out. Tree surgery. — Properly executed tree surgery ^^ sometimes is ef- fective in repairing injury by termites to valuable old fruit and shade trees. Insecticides. — When valuable trees are infested but not yet dying, subterranean termites can be killed in the soil, if it is moist and not too compact, by breaking it up near the tree and pouring carbon disulphide on the earth at a distance of about a foot from the trunk, then covering the liquid over with earth. The gas from this liquid will penetrate the subterranean galleries of the termites. It is some- what dangerous to plant life and very large doses should not be used. Cai'e should he taken in handling this volatile fluid^ as the gas or vapor from it is highly iivfiainmable and explosive when mixed icith air in. certain proportions; no f..ame should he hrought near it, and the fimws should not he inhaled^ as they are poison/ms. There are indications that an emulsion of carbon disulphide, which is on the market ready for use, may prove more effective than carbon disulphide alone; as in the case of the disulphide itself, the earth is loosened up and the emulsion jDOured on, at least a foot from the tree. Carbon tetrachloride,^- the gas from which is neither explo- sive nor inflammable, can be similarly used but is apparently not so effective as carbon disulphide. The gases from carbon disulphide and carbon tetrachloride, being heavier than air, will not readily rise. If tree trunks or branches are infested, they must be treated with poisonous liquids, such as kerosene emulsion poisoned with sodium arsenite.^^ Orthodichlorobenzene is probably useful in the same way. When treating the infested portions, which are usually in the dead heart wood, these liquids must not be permitted to come in con- tact with living plant tissue. Where nonsubterranean termites are infesting living trees, they can be poisoned with dry Paris green in the manner discussed on page 18. VINEYARDS In vineyards all dead or diseased vines should be removed. All exposed areas left by pruning should be painted with preservative coatings and the prunings should be burned promptly. Near-by stands of tree windbreaks should be carefully cared for and kept free from infestation by termites. Trellis posts should be creosoted. FIELD AND TRUCK CROPS Deep fall plowing. — Deep, late, fall plowing will be of value in breaking up the galleries and nests of subterranean termites on ground planted to field or truck crops. Irrigation of the land, where practicable, will be effective; this can be done before planting the crop. "For information on this subject the reader is referred to Farmers' Bulletin 1178, " Tree Surgery," which may be obtained on application to the United States Department of Agriculture. ^ Carbon tetrachloride is a thin, transparent, colorless, volatile liquid, which forms a gas with a pungent, aromatic odor. Like carbon disulphide it is heavier than air. Although it is only about one-half or one-third as effective as carbon disulphide when used at the same do.sage rate, it has the great advantage that its gas is neither explosive nor inflammable ; there will be no fire risk attending its use in buildings. 13 In each gallon of the water used for diluting kerosene emulsion or miscible oil, dis- solve 1 ounce of sodium arseuite. 20 Farmers' Bulletin U72 Burning stubble. — Care should b8 Kerosene emulsion is made as follows : Kerosene. 2 gallons ; fish-oil soap, one-hnlf pound ; water, 1 gallon. Dissolve the soap in hot water and pour in the oil slowly, with constant stirring to emulsify. Dilution : If 37 gallons of water be added to the above stock emulsion it will give 40 gallons of 5 per cent kerosene emulsion. 22 Farmers' Bulletin U72 attack. Provide for air spaces between the ground and wooden flooring and lay concrete floors on a gravel base. In regions where nonsubterranean termites are common (see map, fig. 1) woodwork should be treated with preservatives. To eliminate termites already established in buildings, examine the foundation timbers and other woodwork in tiie basement to determine the ajjproximate point of entrance and the extent of damage already accomplished. After removing the damaged wood, drench the ground with insecticides or poisonous solutions. Then replace the damaged timber with rock, brick, concrete, or metal work, or substitute, for the foundation, timbers impregnated with coal-tar creosote. Since subterranean termites always require access to damp earth, shut off this source of moisture. The insects will then be unable to extend their galleries farther and will perish. Nonsubterranean termites can be killed in infested wood by the use of insecticides. Injury to living vegetation is occasionally serious, especially in the Southern States, the Southwest, and the Pacific Coast States."^ It can be prevented by clean cultural methods, deep fall plowing, and the use of insecticides. U. S. GOVERNMENT PRINTING OFFICE: 1930 For sale by the Superintendent of Documents, Washington, D. C. - - - - Price 5 cents Reprinted from Journal of Forestry Vol. XXVIII, No. 6, October, 1930 TREE DAMAGE BY THE RED SPIDER BY GEORGE S. PERRY TREE DAMAGE BY THE RED SPIDER' By GEORGE S. PERRY Senior Research Forester, Pennsylvania Forest Research Institute Fine webs spun over leaves or leaves appearing gray and dusty or yellowish, may indicate the presence of the Red Spider, whose life cycle, habits, distribution, detrimental activities and control are here discussed. HARVEST mites and red spiders, at times serious pests to trees and plant life, are minute Ara- chnid creatures with a world-wide dis- tribution. They are not really insects, although commonly so considered be- cause of the similarity of their life his- tories and relations to the plant and animal world. Probably the species most frequently met in the eastern United States are Tetranychus telarius with general host habits and often a serious green-house pest, and Bryobia pratensis, the clover mite, which also at times attacks fruit trees. There are, however, numerous species of harvest mites and allied forms with food habits and gen- eral structure like these two. All attack vegetation in about the same way and may be combatted by similar measures. Relatively few of the species are com- monly recognized as pests, chiefly be- cause their very small size enables them to escape notice. Distribution and Abundance The red spider (1) and all of its relatives are contained in the Order Acarina or Acarida, which included 133 genera with 450 species listed in the United States in 1907. In the Order are found species which are parasitic on both plants and animals. Birds are com- monly attacked by mites. A human trouble commonly termed "itch" is caused by a minute Acarid mite. Al- though the red spider is now generally recognized as a nursery pest, it is prob- able that most foresters are even more familiar \n\h "red bugs" or "chiggers," which are the larvae of a small red spider form. The ticks that attach them- selves to dogs, cattle, and sometimes to man are among the largest representa- tives of the group, which feed by suck- ing sustenance from their host. Some very serious diseases of both men and animals are now known to be spread by these relatives of the red spider. Warm and sunny climatic conditions seem most favorable to the order. Among the trees recorded as attacked by red spider in Pennsylvania State Forest nurseries are Colorado blue spruce, Norway spruce, white spruce, Engelmann spruce, arborvitaes, catalpa, honey locust, persimmon, tulip poplar, chestnut, and American elm. The spruces and elm probably suffer the worst. Citrus fruit trees in the South are often severely injured by red spiders and mites. Since this report is written in the in- terests of forestry in Pennsylvania, the 90 -il Toon^"^^'^ ^^ Conference of Pennsylvania Foresters, Mont Alto, Pennsylvania, January 864 TREE DAMAGE BY THE RED SPIDER 865 term red spider will be used hereinafter to designate those species that may feed on the leaves and succulent parts of trees and plants, while the term Acarid will refer to the general group. European forest entomologists for some years past have made accurate determinations of the number and kind of insects hibernating in the forest soil and litter during the winter. By com- parative studies over a period of years, it is possible to know which pest forms are on the increase, and to predict which ones may develop in hordes and become a serious plague. The remarkable fact emphasized by all such census work has been the high representation of red spiders and related life forms ( Acarids) . In practically every instance these made up from 44 to 92 per cent of the total counts on all sorts of sites, from sphag- num and lichen covered tundras of the North to the desert sands of the Sahara. It is reasonable to believe that red spiders and their relatives are just as universally distributed in America as in Europe and Africa, yet only under ex- ceptionally favorable conditions do they become a pest demanding active control measures for the protection of trees and other crops. Almost every year forest nursery in- spectors in Pennsylvania have reported the occurrence of red spiders in the nurseries of the State. In practically every forest tree nursery it is possible to find on needles and leaves the minute pale brown spots or dots that show the work of these creatures, even if they themselves have apparently disappeared. True red spiders (4) spin a dense fine web on the twigs and foliage on which they feed, if present in damaging num- bers. The spiders are so small, however, that even under such conditions, a mag- nifying lens is required to see them. Damage by Red Spiders The life history of T. telarius is well understood, as this species has been known since before the time of Linnaeus. The female of the species over-winters on the lower part of various plants such as moss and grass, or hides in the litter on the ground. In spring it ascends growing plants and lays eggs at the rate of five to ten per day for a period of eight to twelve days. During hot, dry weather these eggs hatch in about four days and the young are fully developed ten to fourteen days later. This life cycle permits about six generations dur- ing a summer season, and if weather and all other conditions were favorable, a single mother might have offspring to the number of 750,000,000,000 by the end of the growing period, if the sexes were equally distributed. This explains why the red spider often becomes very injurious during a protracted drought, when plants are least able to resist the pest. Because of the limited water sup- ply at such times, they cannot replace the sap withdrawn by countless minute but extremely greedy mouths. Under such conditions entire plants and even trees may be defoliated or killed, espe- cially in nurseries where clean culture forces the pest to concentrate on single specimens. Red spiders apparently pre- fer to live and feed in colonies, in which condition they are afforded maximum protection from the fine mesh of webs they spin. Although red spiders are not men- tioned by Dr. E. P. Felt in his "Manual 866 JOURNAL OF FORESTRY of Tree and Shrub Insects," and are either not listed or only casually dis- cussed in other publications on tree pests, they certainly deserve more con- sideration. Pennsylvania has had seven large forest tree nurseries within its borders. In four of these it has been necessary at times to take active control measures against spiders. The necessity would probably been more frequent and acute if good irrigation and shad- ing facilities were not usually provided. The dependence of red spiders on hot, dry weather, is helpful to the nursery- man, since he need not fear trouble under other conditions. This character- istic, however, has probably caused these small pests to be seriously underesti- mated and generally overlooked, since trees that suffer more or less severely from spider attacks at such times are commonly assumed to be suffering from drought. Closer examination would re- veal the red spider as an important con- tributory factor in their failure. District Forester H. M. Nicholas re- ported a very definite case of plantation loss from the red spider during the dry summer of 1929. This occurred in a plantation of 15,000 white pine trees planted in Roaring Brook Township, Lackawanna County, in 1915. In 1929 the trees averaged 10 feet in height, and some of them were 20 feet tall. Eight per cent of all the trees were killed out- right by the red spider attack, and 7 per cent were injured to the extent that their foliage turned yellow and sickly in appearance. When trees, especially evergreens, are planted, either for forestry or orna- mental purposes, there is often injury and loss from spider damage. The danger is greatest when trees are set on warm, dry south slopes, or on the sunny, south and southwest sides of buildings. Many trees die during their first year on such sites because red spider colonies develop and work seri- ous injury before the trees recover from the shock of transplanting. Neglected lawns and abandoned fields often harbor the red spider, where it is ready and waiting to attack any new and favorite host that may be introduced. Sometimes the pest is present on nursery stock when shipped. In the tree nursery operated by the Pennsylvania Department of Highways near Lewisburg there has been considerable trouble with the red spider. It is possible that the infesta- tion originated in the Mont Alto Nurs- ery, as it was first noticed on stock that was transferred from the latter nursery, where the pest recurred over a period of five successive years, whenever weath- er favored it. Control Measures This emphasizes the necessity of keep- ing nursery stock free of these mites. They can be combatted easily in the nursery or on individual ornamentals, but the forester can do little in a prac- tical way to protect extensive planta- tions, if the pest is generally established, because of the excessive cost. A hard, driving summer rain is most effective in controlling infestations of red spiders. Planted trees and shrubs on lawns can be often satisfactorily treated with water, applied at high pressure with a hose, so as to destroy the spiders or wash them away. However, water treatment should not be considered sufficient in a nursery. All infested nursery stock should be thoroughly sprayed to guar- TREE DAMAGE BY THE RED SPIDER 867 antee that the pest is eliminated and will not be scattered far and wide to places where it may do much damage — often before its presence is known. Any contact insecticide is effective against red spiders. Kerosene emulsion, other miscible oils, lime-sulphur and nicotine sulphate are all good. They should be applied twice, with an inter- val of about ten days between applica- tions. Powdered lime, wood ashes, flowers of sulphur, and soot sifted over trees when covered with dew, have been some of the measures used in the State Forest nurseries of Pennsylvania. The results have been beneficial, but careful spray- ing with insecticides is undoubtedly better. The extent to which birds eat the red spider and mites is not known definitely. The pest is always worst on low growth in the open and on such trees as spruce, whose prickly needles discourage bird visitation. The United States Biological Survey (5) has made some very careful studies of the foods of birds based on stomach contents, yet only rarely are these life forms listed. This is explained by their extremely small size and fragile structure which renders identification impossible. There is little doubt that wrens, warblers, kinglets, chicadees, creepers, nuthatches, and vireos eat these pests. Such birds deserve pro- tection for they are of the greatest im- portance in keeping under control nearly all kinds of injurious insects, as well as red spiders. Summary It is probable that the red spider is doing more injury to trees in Pennsyl- vania than is generally realized. It is ad- visable that foresters, nurserymen, and gardeners be informed about this minute pest and learn to recognize its presence. Sometimes the naked eye can detect the fine webs spun over the leaves or needles of host species, or they may look gray and dusty or yellowish, particularly after a period of dry weather. Such trees or shrubs should be carefully in- spected with a good hand lens or read- ing glass, and in a surprising number of cases the pale pin-point feeding dots will be found. If the pests are still pres- ent, their pearly eggs or their remnants will be noticed, together with the busy eight-legged reddish mites. A twig or leaf which appears to be attacked by the red spider, if sent to the Department of Forests and Waters at Harrisburg, or to the Pennsylvania Forest Research In- stitute at Mont Alto, Pennsylvania, will permit of verification and will bring specific recommendations for helpful control measures, when requested. References 1. Comstock, John H. The Spider Book, Doubleday, Page & Co., New York City, 1920, pp. 85-88. 2. Russell, John. Microorganism of the Soil, London, 1923. 3. Tragardh, Ivar. Svenska Skogsv&rds- foreningens Tidskrift, 1928, pp. 795- 809. 4. Insects Injurious to Deciduous Shade Trees and Their Control. United States Department of Agriculture Farmers' Bulletin 1169, p. 93. 5. Food of our Important Flycatchers United States Department of Agricul ture Biological Survey Bulletin 44 p. 63. Chapin, E. A,, Food of Vireos United States Department of Agricul ture Bulletin 1355, p. 28.