¥7.C fA S 2 F Gniversity of Maine. | oy on tee : r 5.256 THE ROYAL CANADIAN INSTITUTE ological . Medical serials Maine Agricultural Experiment Station NH S BULLETIN 256 NOVEMBER, 1916 et ELM LEAF ROSETTE AND WOOLLY APHID OF THE APPLE. ISSUED UE mh pees : CONTENTS. : PAGE Nigas Pipa eee General Discussion. ..... 2.2... 0. ee eee 330 Se EN SS ay ey o's 2 a yee cmd ae dt eee lees 336 Life Cycle of Woolly Aphid of Apple.................. 338 os gc pee a ce e's oelel ele Sa wines 339 I gs cede a ine oie cere ee oe os 340 Preventive and Remedial Measures......:./........... 341 & gerbes 4 - MAINE AGRICULTURAL EXPERIMENT STATION ORONO, MAINE. THE STATION COUNCIL. PRESIDENT ROBERT J. ALEY, President DIRECTOR CHARLES D. WOODS, Secretary CHARLES L. JONES, Corinna, Committee of FREELAND JONES, Bangor, Board of Trustees WILLIAM T. GUPTILL Topsham, Commissioner of Agriculture EUGENE H. LIBBY, Auburn, State Grange WILSON H. CONANT, Buckfield State Pomological Society FRANK S$. ADAMS, Bowdoinham, State Dairymen’s Association LEONARD C. HOLSTON, Cornish, Maine Livestock Breeders’ Association WILLIAM G. HUNTON, Readfield, Maine Seed Improvement Association AND THE HEADS AND ASSOCIATES OF STATION DEPARTMENTS, AND THE DEAN OF THE COLLEGE OF AGRICULTURE. THE STATION STAFF. ( CHARLES D. WOODS, Sc D. Director ADMINIS- ; BLANCHE F. POOLER, Clerk TRATION }\ GEM M. COOMBS, Stenographer | JANIE L. FAYLE, Stenographer ( RAYMOND PEARL, Pu. D., Biologist | FRANK M. SURFACE, Pu. D., Biologist BIOLOGY | MAYNIE R. CURTIS, Pu. D., Assistant JOHN R. MINER, B. A., Computer | MILDRED REBECCA COVELL, Clerk JAMES M. BARTLETT, M. S., Chemist HERMAN H. HANSON, M. S., Chemist CHEMISTRY 4 JOHN H. PERRY, Assistant | WILLIAM H. RICH, B. S,, Assistant WALTER W. WEBBER, B. S., Assistant HARRY C. ALEXANDER, Laboratory Assistant ie EDITH M. PATCH, Pu. D., Entomologist ALICE W. AVERILL, Laboratory Assistant WARNER J. MORSE, Pu. D., - Pathologist PLANT +MICHAEL SHAPOVALOV, M. S. Assistant PATHOLOGY TGLEN B. RAMSEY, A. M., Assistant DONALD S. CLARK, Laboratory Assistant AROOSTOOK JACOB ZINN, Acr. D., Assistant Biologist FARM }< C. HARRY WHITE. Scientific Aid EREMIAH E. SULLIVAN, Superintendent HIGHMOOR ee SINCLAIR, Superintendent FARM34 ace E. CURTIS, Scientific Aid ROYDEN L. HAMMOND, Seed Analyst and Photographer CHARLES C. INMAN, Assistant / fIn collaboration with U S. Department of Agriculture. BULLETIN 256. ELM LEAF ROSETTE AND WOOLLY APHID OF THE APPLE.* Schizoneura lanigera (americana in part). EpitH M. Patcu. White masses looking like patches of thick mold often occur on apple trees, especially about pruning wounds or other scars on the trunk and branches and upon water sprouts. Beneath this substance are colonies of rusty colored or purplish brown plantlice known as “woolly aphids” on account of the appear- ance of white covering which is, however, really composed of waxen filaments. The species is common in Maine on hawthorn, mountain ash, and Baldwin and some other varieties of apple. It is one of the migratory aphids and passes part of its life cycle upon the elm,** as is explained in the following treat- ment. It should not however, be confounded with those woolly aphids found upon alder} and maple,f£ as the woolly aphid oi the apple cannot live upon those trees. *Papers from the Maine Agricultural Experiment Station: Ento- mology No, 91. The work upon which this bulletin is based was for the most part completed in 1913 and published by this Station as Bulle- tin 217, which is now out of print. As the interest in the insect con- cerned continues and as the discovery of its annual migration from elm to apple was first recorded by this Station, it seems desirable to print this revised edition of Bulletin 217, containing such changes as bring the subject down to date. Cuas. D. Woops, Director. **There are other elm aphids belonging to this same genus which do not migrate to apple. TPemphigus tessellata (acerifolit.) tPemphigus tessellata (acerifoli) and Pemphigus aceris. 330 MAINE AGRICULTURAL EXPERIMENT STATION. 1916. HABITS AND GENERAL DISCUSSION. The woolly aphid occurs upon the apple as a bark feeder and is found upon branches, roots, and tender places on the trunk. These insects are covered by a white flocculent waxy secretion given off as fine filaments through pores in the skin and their colonies are thus readily detected by the masses of white “wool” which renders them conspicuous. Figs. 58 and 67. On the roots its attacks induce enlargements and in the creases of these malformations the root form occurs in clus- tered masses. The injury to the trees is due both to the suck- ing up and exhaustion of the vital plant juices and to the poisoning of the parts attacked, as indicated by the consequent abnormal growths. Fig. 66. The damage is particularly serious in the case of nursery stock and young trees and is less often important after the tree has once become well established and of some size, though it may be troublesome then, too. Where this insect is abundant all the roots of a young tree to the depth of a foot or so become clubbed and knotted by the growth of hard fibrous enlargements with the results in a year or two of the death of the rootlets and their ultimate decomposition with subsequent disappearance of the galls and also of the aphids, so that after this stage is reached the cause of the injury is often obscure. On the trunks the presence of the aphids results in the rough- ening of the bark or a granulated condition which is particu- larly noticeable about the collar and at the forks of branches or on the fresh growth around the scars caused by pruning, which latter is a favorite location. On the water shoots, they collect, particularly in the axils of the leaves, often eventually causing them to fall, and on the tender growth of the stems. The dam- age above ground, even when insignificant, is useful as an indication of the probable existence of the aphids on the roots. A badly attacked tree assumes a sickly appearance and does not make satisfactory growth, and the leaves become dull and yel- lowish, and even if not killed outright it is so weakened that it becomes especially subject to the attacks of borers and other insect enemies. The common forms both on the roots and above ground are wingless aphids, not exceeding one-tenth of an inch in length, ELM LEAF ROSETTE AND WOOLLY APHID OF APPLE. 331 of a reddish-brown color, and abundantly covered, especially in those above ground, with a flocculent waxy secretion. Fig. 63. In August and later, among the wingless ones, winged females appear in abundance. Fig. 62. They are little, clear-winged aphids which look nearly black unless carefully examined when the abdomen is found to be dark yellowish red or rusty brown. These are the fall migrants that leave the apple and seek the . elm before giving birth to the generation of true sexes,—minute, wingless, beakless creatures, the female of which deposits a single “winter egg”’ within a crevice of the elm bark. The flight of the fall migrants away from the apple is appar- ently a common observation of all who have studied this species either in this country or abroad,* but it is only recently that the significance of this flight has been appreciated, it having been thought previously to be merely a dispersal from one apple tree to another. Where woolly aphid colonies are very thick, the true sexes and the winter eggs are sometimes found upon the apple tree. That such occurrences are accidental seems probable as fall migrants of most species will occasionally dispose of their pro- geny before reaching the appropriate winter host. A record of such an occurrence is to be found in the Report of the Entomologist of the United States Department of Agriculture for the year 1879 by J. Henry Comstock. On page 259 of this Report, Dr. L. O. Howard recorded his observations made in a little orchard of Russian apple trees then on the grounds of the Department of Agricul- ture at Washington, his statement concerning the winter egg being as follows: “The winter egg was found on several occasions during the winter in crevices of the bark over which a colony had been stationed during the summer. It was a rather long ovoid, measuring .322 mm. (.125 inch) in length and was very similar to the winter egg of Colopha ulmicola (Fitch), as described by Riley in Bulletin No. 1, Vol. V, Hayden's Survey. “This egg was laid, as Professor Thomas supposes, by a wingless female, differing from the ordinary agamic form to a certain extent. These females we only know from finding their skins around the winter egg, since they often die without depositing it. The males we have iiot seen.” *Dr. O. Schneider-Orelli records also the development of winged forms in June. ' Sonderabdruck aus Heft 7/8 des XII. Bandes der Mitteilungen der Schweizerischen Entomologischen Gesellschaft. 1915. 332 MAINE AGRICULTURAL EXPERIMENT STATION. 1916, Mr. A. C. Baker of the Bureau of Entomology wrote me (Nov. 20, I9g12): “I found that when the colonies are very thick the alate forms often stay on the apple and I have found on one tree a number of winged ones with the abdomen shriveled as it is after producing sexes. I saw some sexes crawling up and down the small twigs and though I have not yet seen any eggs which they laid they no doubt would lay eggs. On one occasion I found sexes on an apple leaf which had fallen to the ground.” That such occurrences are not a part of the ordinary life cycle is indicated by the usual wholesale flight of the fall mi- grants.* On the elm the stem mother, which hatches from the over- wintering eggs sheltered probably in rough crevices of the bark, appears early in the spring and may be found in Maine before the middle of May stationed on the partly opened leaf buds. The beak punctures on the rapidly expanding new leaves cause an unevenness of growth which forms a protection for the aphid. By the last of May the earliest of these wingless stem mothers are mature and found in the deformed elm leaves (Fig. 59) producing the next generation. The antenna is shown in Fig. 68. These nymphs, like the stem mother, are a wingless form and they become fully developed about the tenth of June. They have wax glands, of the type shown in Fig. 61. Their progeny are the third generation and attain wings. These winged aphids are known as the spring migrants. It takes three weeks or slightly more or less, beginning about the twentieth of June, for all the individuals of this third gen- eration to get their growth so that the migration covers a con- siderable period. The deserted rosette or leaf cluster at this time looks like Fig. 60. During this time these winged aphids may be found alighting on the leaves of apple, mountain ash, *1904. Alwood, Wm. B. Circular in Relation to Some Injurious Insects and Plant Diseases. Special Bulletin (C. P. C. 45), Va. Exn. Sta. 1908. Gillette, C. P. Notes and Descriptions of Some Orchard Plant Lice, of the Family Aphidide. Journal of Economic Entomology, Voi. I, pp. 306-308. 1909. Borner, Carl. Kaiserliche Biologische Anstalt fiir Land-und Forstwirtschaft, August. 1913. Reh, L. Der Praktische Ratgeber im Obst—und Gartenban, February 2. ELM LEAF ROSETTE AND WOOLLY APHID OF APPLE. 333 and hawthorn. They creep to the under side of the leaf and remain there while they give birth to their progeny (i. e., the fourth generation). These young, before they feed at all, crawl ‘to the stem of the water-shoots, or to some tender place on the bark often near a pruning wound, and there start the colony on the summer host plant. Such a young colony shown in Fig. 67, was on a mountain ash in Orono of which I kept a record during the season of 1912. The main trunk of this tree was dead nearly to the ground, but I2 vigorous shoots had grown up measuring about 5 feet each. On June 28 this mountain ash had about 150 woolly masses of nymphs grouped on the stem at the leaf axils. These nymphs ranged from very tiny ones to half grown insects, none being mature at that date. One such woolly mass contained 155 individuals of various sizes. (See Fig. 67). On the ventral surfaces of the leaves of this mountain ash were stationed many elm leaf migrants producing there their broods of nymphs which could be seen, with the hand lens, to be augmenting the woolly masses on the stem. Collections of these migrants thus stationed were made as follows :—July 2, 88 migrants; July 3, 211 migrants; July 5, 92 migrants; July 8, 54 migrants; July 9, 80 migrants; July 10, 33 migrants; July 12, 14 migrants; July 12, 3 migrants. Only living individuals were collected, dead ones being brushed off and discarded in the counts. Microscopic examination showed them to be identical with winged forms collected in elm leaf. Two large elm trees with leaves well stocked with this species stood about a rod distant.* In this connection it may be of interest to record a forced migration test. On June 21, 1912, I placed several hundred elm leaf migrants at the base of water shoots of an uninfested mountain ash on the Campus. As the migrants are much more docile about sundown than earlier in thie day this was done about 7 P. M. They moved but little, most of them creeping to the ventral side of a leaf and remaining there; and during the night producing nymphs which sought the leaf axils of the water shoots so that by the afternoon of June 22, the tiny nymphs had already fed enough and secreted enough white wax to give the typical “woolly” appearance to the young colonies. These and the progeny thrived on the mountain ash in a perfectly normal way. On June 17, 1913, a laboratory cage check was started with migrants from an elm rosette. The winged forms ready to desert the elm leaves were caged with a seedling mountain ash. Their progeny settled in woolly masses on the stem of the seedling and are shown in Fig. 58. By July 2 these had matured and were producing young which in turn had matured and were producing nymphs on July 26. This third moun- tain ash generation (sixth generation beginning with the stem mother) *Previously recorded in Journal of Economic Entomology, Vol 3, No. 5, 1912. 334 MAINE AGRICULTURAL EXPERIMENT STATION. IQI6. proved too much for the little seedling which was so nearly dead by August 10 that the last of the aphids perished at that time. Schigoneura americana is a name which until recently has been com- monly applied to two distinct species by American entomologists. One of these species inhabits the leaf cluster or aphid rosette of the American Elm (Figs. 59 and 60). This migrates to apple, several varieties of mountain ash (Pyrus sp.) and to hawthorn (Crataegus), where it was familiar as lanigera long before its identity with the aphid of the elm rosette was suspected. The life cycle of this species so far as personally ascertained by the writer is recorded in the present paper. This species is found in Maine, Missouri, Colorado* and doubtless all the way between. Like other aphids it is fluctuating in its abundance, being conspicuous some years and comparatively rare during other seasons. *That Messrs. Gillette and Bragg were mistaken in their opinion ‘hat the rosette aphid in Colorado did not migrate to the apple in accord- ance with its habit in Maine (Journal Economic Entomology, Vol. &, p. 100) is shown by the observations of Mr. Maxson (Entomological News, Vol. 26, pp. 367-368). Although Professor Gillette has not vet published his later observations, so far as we know; that they agree with those of Mr. Maxson is indicated in a letter from him to the writer under date of June 25, 1915, from which the following paragraphs are quoted: “You will be interested to know that the rosette form of the elm Schizoneuran is very common about Fort Collins this year, and the winged forms are now leaving the leaf clusters in great numbers, and for the first time since we began the study of this insect, we find the lice locating in considerable numbers upon the under side of the leaves of apple trees. “In many instances we are able to find the young that they are depos- iting, and in many instances, also, it seems probable that a colony of young lice in the axils of the leaves are the product of these winged lice from the elm. So it begins to look as though we shall have to admit that there is a natural migration of this elm Schizoneuran to our apple trees. “We had been able, repeatedly, to get these lice to take in small num- bers in our breeding-cages, and I find that last year Mr. Maxon of Longmont had found this louse going to the apple in the field, but until a few weeks ago, he had not communicated the fact to me. It really — looks now as though our observations here would fully confirm your observations in Maine.” The experiments of Mr. Baker proved that in the socalities in which he worked the elm is the winter host of lanigera (Report No. ror, U. S. Department of Agriculture, Office of the Secretary. 1915). The life cycle of this aphid, therefore, as discovered for Maine by the writer, does not seem to be exceptional for America. ELM LEAF ROSETTE AND WOOLLY APHID OF APPLE. 335 The other species to which the name Schizoneura americana has beeit commonly applied is the aphid discussed in Bulletin 241 of this Statiou. Since the name lJanigera takes care of the rosette species on elm as well as on apple, S. americana seems to be left conveniently for the aphid curling or rolling the leaf of the American Elm (Fig. 45 of Bulle- tin 241). Riley’s description of the leaf deformations caused hy S. americanay indicates clearly enough that he originally applied this name to both these species as his successors have certainly done unr) recently; and the synonomy “Schizoneura lanigera (americana in pact, of authors),” correctly designates the “rosette aphid” of the elm. There are apparently 3 summer generations of progeny of the elm leaf migrants upon the apple in Maine,—two apterous gen- erations followed by a generation part of which, the fall mi- grants, become winged and leave the apple and part develop into apterous forms and remaining on the apple give birth to nymphs which while still young seek protection at the base of the tree for the winter and are known as the hibernating nymphs. It is the function of the migrants to seek the winter host and there give birth to the true sexes. These are the tiny yel- lowish brown egg-laying females and the still smaller pale yel- low males. Both sexes are wingless and with rudimentary mouth parts which are apparently functionless. One compara- tively large yellow egg occupies nearly the whole abdomen of the female and with the deposition of this the cycle of the spe- cies closes,—or begins. It is too complicated a performance to follow easily but the outline on page 338 will be useful as a ~ summary. Such a cycle with the annual migration to and from the apple with the elm serving as host for the first three spring generations is undoubtedly typical for lantgera. The hibernat- ing nymphs which remain protected about the crown of the apple over winter and ascend to tender places on the bark before feeding in the spring give what looks like a “closed cycle” of apterous viviparous females persisting on the apple. How long “Curling and gnarling the leaves of the White Elm (Ulmus ameri- cana), forming thereby a sort of pseudo-gall. The curl made by a sia- gle stem-mother in the spring takes the pretty constant form of a rather wrinkled roll of one side of the young leaf, but according as there is more than one stem-mother, or as several contiguous leaves are affected, the deformation assumes various distorted shapes, sometimes involvinz quite large masses of the leaves.” 330 MAINE AGRICULTURAL EXPERIMENT STATION. IgQI6. such a colony could maintain itself on the apple without fresh material from the elm I do not know.* I am certain that in Maine the natural enemies of the woolly aphid would cut its career short and that it would not assume the status of a pest of consequence if it did not shift its food plant. As it is, a two days quest in the vicinity of Orono early in September, 1913, failed to locate a single colony which was not well nigh demolished by chalcid parasites and the colonies of 1912 met a similar fate the preceding year by virtue of syrphus maggots. Lady bird beetles are also very active some seasons. While in the elm leaf this aphid is preyed upon by syrphus maggots, capsid bugs and lady birds. As if the hibernating nymphs were not enough to bewilder one, the case of the woolly aphid of the apple is still further complicated by the root colenies which although hidden in their operations are really often much more pernicious than the colo- nies on trunk and branches. These root colonies ordinarily remain underground all the year round, apparently until the roots become too badly demolished for feeding purposes. Economic STATUS. “ The danger from the woolly aphid is greatest to nursery stock and young orchards. Mr. Marlatt (Journal of Economic ‘Entomology, Vol. 4, pp. 116-117) in recording the use of American-grown apple seedlings says:—“Mr. F. W. Watson, of Topeka, Kans., in an article in the National Nurseryman for January, I910, p. 437, on ‘American-grown Apple Seedlings,’ states that from twenty to forty million of American-grown apple seedlings are used in this country every year, the pro duction of about a dozen nursery firms. The bulk of the seed used comes from France, and therefore is of the same stock as the imported French seedlings.” Mr. Lohrenz (1911) in recording observations on two-year- old nursery stock made at three nurseries containing respectively *We have an exact parallel in Pemphigus tessellata or the woolly aphid of the alder with a cycle including a spring migration from the maple leaf to alder and a fall or return migration to the maple and also a generation of hibernating nymphs remaining under leaves about the base of the alder during the winter and ascending to the stem hefore feeding in the spring. ELM LEAF ROSETTE AND WOOLLY APHID OF APPLE. 337 about 30,000; 45,000; and 300,000 trees, states that he found from 20 per cent to 25 per cent of the trees infested by the woolly aphid. In circular No. 20, Bureau of Entomology U. S. Department of Agriculture (revised edition 1908) the woolly aphid of the apple is characterized as “one of the worst enemies of the apple.” Mr. Alwood (1904) of the Virginia State Crop Pest Com- mission in his excellent account of this insect states “On nur- sery stock the woolly aphis is a most serious pest, and under some circumstances it ruins a large percentage of the apple trees in the nursery.” On page 5 of Bulletin 133 of the Colorado Experiment Sta-~ tion the following statement is made: “Tf Colorado orchardists should vote their opinion as to what ought to be called the worst orchard pest in the state, it is very doubtful whether the codling moth, or the woolly aphids, would carry off the honors.” Although it would be easy to compile testimony of this char- acter against the woolly aphid as an enemy to young apple trees from numerous and widely separated parts of our country, they would be chiefly a repetition of what has already been said. During those seasons when the species is abundant it is also a serious pest on American elm. Some springs in the vicinity of Orono practically every branch of many trees is tipped with an unsightly cluster of deformed leaves or “rosette” gall. Such an infestation, to say the least, mars the beauty of a large tree and is a heavy handicap for a young one. 338 MAINE AGRICULTURAL EXPERIMENT STATION. IgI6. LIFE CYCLE OF WOOLLY APHID OF APPLE. (Exclusive of root forms.) ELM: Primary Host. Apple: Alternate Host. EGGS. NYMPHS. (Under bark all winter) (Hibernating young mi- —_———————_ grating to trunk or branches in early spring) STEM-MOTHER. (first generation in leaf. Apterous viviparous females). SECOND GENERATION. SEVERAL GENERATIONS. (apterous viviparous females in leaf). SPRING MIGRANTS Migrates to apple (third generation. Alate viviparous). ‘ FOURTH GENERATION. (apterous viviparous females). FIFTH GENERATION. (apterous viviparous females). Migrate to elm . ay SOL TLL MGR RES APTEROUS VIVIPAROUS (Alate viviparous PARTHENOGENETIC parthenogenetic FEMALES, mature in females, mature Aug.-Sept. Aug.-Sept. APTEROUS OVIPAROUS FEMALES sexuparae. ) AND APTEROUS MALES. HIBERNATING NYMPHS EGGS. (protected during winter (under bark all winter). about crown of tree). ELM LEAF ROSETTE AND WOOLLY APHID OP APPLE. 339 STRUCTURE KEY. Woot_ty APHID OF APPLE. A. Apterous forms. Antenne without annulations. B. Females. C. Viviparous. D. Antenna typically 5-jointed, Fig. 68. Wax glands not of type shown in Fig. 61. First spring generation hatched from over-wintering egg and found in elm soseite cariye.im! June. ..12. 3 vowedew avs Stem Mother. DD. Antenna 6-jointed. Fig. 68, No. 80. Wax glands as shown in Fig. 61 and Fig. 68, No. 80. Progeny of stem mother developing in rosette in June EE Eee hia lee oa Second Elm Generation. DDD. Antenna 6-jointed. Fig. 68, No. 82. Wax glands of same type as those shown in Fig. 61. On apple bark or WFAFOE SHOOTS |. Galas Su nd. eb. tice Summer Generations. DDDD. Structure about as with summer generations On appie FOOTS all times -Of (Wear s055% 56-5 Root Generations. DDDDD. Young born late in fall and living over. winter about crown of tree, apparently without feeding until spring, when they ascend to apple bark and attain their CEE 1b alewidiscde Cetin w aie Jig cla hls ons Hibernating Nymphs. CC. Oviparous. Antenna 5-jointed, Fig. 64. Minute beakless form which deposits the over-wintering egg. Rarely seen but easily obtained by imprisoning fall migrant in vial.. True Female. BB. Minute beakless form smaller and more slender than true female. Antenna 5-jointed. Fig. 65. Rarely seen but easily obtained, by imprisoning fall migrant in vial................ True Male AA. Alate forms. Antenne with annulations. B. Antenna typically with III as long as or longer than IV+-V-+ VI. VI typically without annulations. Fig. 68, No. 81. Developing in June-July in elm rosette and migrating to apple, hawthorn and mountain ash. Progenitor of summer generations ers Serenata S.C wie albany, dines « aolaeom eet ete amee do ao Spring Miarant BB. Antenna much as in spring migrant, though usually shorter. VI typically with 2 or more annulations. Fig. 68, Nos. 83, 84, 85. Developing in fall in woolly colonies on bark of apple, haw- thorn and mountain ash. Fig. 62. Progenitor of true males RAVER ERRERME SC. i's uty lt Rates oir a a edanl ord ak Sigtemincamwis Fall Migrant 340 MAINE AGRICULTURAL EXPERIMENT STATION. I9QI16, HABITAT KEY. WooLty APHIDS OF THE ELM. A key to aid in distinguishing the woolly aphid of the apple from the other elm species with which it may easily be confused in the spring of the year. A. Conspicuous woolly colonies on bark of Ulmus americana. Throughout the summer on young elms. No alternate hest known. Widely distributed in America............... S. riley. AA. Spring generations in elm leaves, causing various types of deformation. B. Large baggy gall on Ulmus campestris. Alternate host un- known. European species. Taken in Connecticut in 1913 SES LT © ON a ee ee oe ae me Perera S. lanuginosa. BB. Terminal leaf cluster or rosette (Figs. 59-60) on Ulmus ameri- cana. Spring migration to apple, mountain ash, and haw- inet weatwne to Colorado...4)000s.. 72.9 eit 5 ee wtceeetc ae. S. lanigera (americana in part, of authors). BBB. Leaf curl or roll type of deformation, C. Leaf roll of Ulmus scabra and U. campestris. Antenna of winged generations with V and VI without annulations. Spring migration to gooseberry and currant. European species. In America found in California, Oregon and ON) ELE, Be 3S 2 ta arr rr S. ulmi (fodiens). CC. Leaf roll of Ulmus americana, Second apterous spring gen- eration with wax gland distinctly unlike those of Fig. 61. Spring migrant with antenna typically with III not longer than IV+V-+VI. Alternate host Amelanclier the roots of which are infested.* Maine to California Be Catttanicee aks ies % S. americana in part, of authors. *Bulletin 241. Maine Agricultural Experiment Station. ELM LEAF ROSETTE AND WOOLLY APHID OF APPLE. 341 PREVENTIVE AND REMEDIAL MEASURES. The foregoing account of the habits and characteristics of the woolly aphid will suggest certain measures to control it. The protection of seedling apples from infestation by the woolly aphid while still in the nursery has heretofore been an exceedingly difficult matter it would seem from the amount of infested stuff that is yearly condemned. But with the know}- edge that the source of danger lies in the migrants from the previously unsuspected elm leaf, it is seen to be possible to con- trol the nursery stock by establishing nurseries at a safe distance from susceptible elm trees or clearing out the elms from the vicinity of large nurseries. As there are many places in the country where the elm is not at all abundant this would often be entirely practicable and where so would be the simplest and most effective method of protection. As it is the seedling trees that are most susceptible to injury and when attacked most seriously damaged by the woolly aphid a method of protection for the young trees while in the nursery is the most desirable. The raising of the elms and apples in the same nursery is thus seen to be a hazardous proceeding and should be avoided. Again young orchards of clean stock set in parts of the coun- try where the elm is not grown should be successfully protected by excluding elms from the choice of shade trees. Indeed, the matter of alternate hosts of the aphid enemies concerned should always be borne in mind in planning the trees for an estate, and only one of the two hosts necessary for the life cycle of a migratory aphid planted, where the pest is a serious one. It is desirable that data concerning the relative susceptibility of different varieties of apple should be accumulated with a view to using the more resistant for root stock, if otherwise practicable. In dealing with infested apple trees the aphid masses on trunk and branch present no especial difficulty, and can be very readily exterminated by the use of any of the washes recommended for plant-lice, such as tobacco decoction, kerosene emulsion, a strong soap wash (Formulas A, B, C, D), the only care necessary being to see that the wash is put on with sufficient force and thoroughness to penetrate the covering and protecting cottony secretion. If the wash be applied warm, _ its penetration will be considerably increased. | 342 MAINE AGRICULTURAL EXPERIMENT STATION. Ig16, An August spray to kill out colonies before the migrants flv and the hibernating young are produced is particularly desirable. The much more important root feeders, however; are more difficult to reach and exterminate. The common recommenda- tions are of applications of strong soap or tobacco washes to the soil about the crown, or soot, ashes, or tobacco dust buried about the roots; also similarly employed are lime and gas-lime. Badly infested nursery stock should be destroyed, since it would be worth little even with the aphids removed. Some nurseries are said to make a practice of “puddling” roots of infested stock, that is packing mud about the roots to conceal their condition. Before purchasing puddled nursery stock, the buyer should insist that the mud be washed off thor- oughly so that the roots are exposed for inspection. Proper cultural methods can hardly be overestimated in their value as a protection of young trees, as neglected orchards not only suffer heavily but serve as a breeding ground, dangerous to the neighboring trees. ForMuULA A—Tosacco DeEcocTION. Tobceo’ stems or tobacco} dust.SSe).\. ls tee 2 pounds NLC I ae ani fis we orcs Sitetele-< ec gine od Rl 4 gallons Put the tobacco in the water, enough to cover, which may be either cold or hot. Place over the fire and when the water has reached the boiling point, remove some of the fire and allow the water to simply simmer for fully one hour, when the liquid is ready to be drained off, diluted to the above proportions and applied. Boiling violently drives off the nicotine. If whole-leaf tobacco is used, prepare as above, using one pound ot tobacco to each four gallons of water. No lime of other alkaline substance should be added to the tobacco while cooking. Apply at once, or within a few days after making if possible. Certain reliable extracts such as “Black Leaf,” “Black Leaf 40,’ and “Nikoteen” are on the market and can be secured through local drug- gists. (The Black Leaf preparations are manufactured by The Ken- tucky Tobacco Product Company, Louisville, Ky., and are carried by the Collins Hardware Company, 97 Friend St., Boston, Mass. Nikotcen is manufactured by The Nicotine Manufacturing Company, St. Louis, Mo., and can be secured from Joseph Brick & Sons, 47-54 N. Market St., Boston, Mass.). Directions for use come with the products. There is nothing to do in the preparation of these extracts except to stir the contents of the ELM LEAF ROSETTE AND WOOLLY APHID OF APPLE. 343 can before pouring out any quantity for dilution. In most cases one gallon of the Black Leaf will be found sufficient for each seventy gal- lons of water. But if in the treatment of any louse this does not seem sufficient it may be used in preparation of one gallon to sixty or sixty- five gallons of water. Careful sprayers have usually succeeded in killing plant lice with this preparation in the proportion of one gailon to each one hundred gallons of water. Thoroughness of application is of as much importance as the strength of material used. Nikoteen is a more concentrated abstract, 1 part being used with from 400 to 600 parts of water. Black Leaf 40 is a concentrated solution of nicotine-sulphate and is widely and successfully used in large western orchards, at the rate of I part to 800 or goo parts of water. It is the common practice to add soap,—whale oil soap or good !aun. dry soap at the rate of 2 bars to 50 gallons. This is to lessen the formation of drops, causing the spray to cover surfaces more in the form of thin film. Better success is obtained by some by using a little lime instead of soap, the inert solid in suspension aiding the extract to “wet” and “stick’ to the bodies of the aphids. For this purpose rt pourd oi stone lime, slaked and strained into 50 gallons of tobacco extract as prepared for application, is sufficient. ForMULA B.—KEROSENE EMULSION. ia eiee SO yh ee are ct ie SPSS: ceca ees. kes I-2 pound Pe EOL. 3) Dye ee RS RE eo nM Lu. 1 gallon ERT VE ESS OSA RI SO ne) Re a 2 gallons To prepare dissolve one-half pound of soap in one gallon of soft water by boiling; when well dissolved and still boiling hot, remove from the fire and add two gallons of kerosene, and agitate at once as briskly as possible. The emulsion is more readily made if the Kerosene first be heated by immersing the vessel containing it in a larger vessel of boiling water. Never heat the kerosene over a direct fire. If large quantities are being made, a good way to emulsify is to use a force pump and spraying nozzle and pump the mixture as forceiully as possible back into the vessel containing it. If the emulsion is prop- erly formed, the whole mass will appear much like whipped cream and will mix readily in water without a film of oil rising to the top. As soon as emulsified, add twenty-seven gallons of water and use at once. This will make thirty gallons of the mixture, and such an emul- sion will be one-fifteenth oil (or a 7 per cent emulsion). This is the strength ordinarily used for the destruction of insects upon plants. For larger or smaller quantities, prepare in the same proportions. Sometimes the emulsion is not perfect and a little oil rises to the tep. In such cases, if the last in the barrel or tank is pumped out upon the 344 MAINE AGRICULTURAL EXPERIMENT STATION. Ig16, foliage, it is likely to burn it. So it is advisable, unless the emulsion is of good quality, to throw out the last few gallons, making no use of it. It is best to dilute and apply kerosene emulsion as soon as it is pre- pared. Avoid using alkali or any hard water in making the emulsion, as it will cause the oil to separate and rise to the top. Any clean, soft water will usually give good results. FormMuta C.—Miscrsrte O1ts. There are several miscible oils upon the market which may be added directly to water forming a milky emulsion at once. In the preparation of any of these, such as “Scalecide,” or “Target Brand Scale Destroyer” or “Killoscale,’ add the oil directly to the water with a little stirring. One gallon of the miscible oil in 30 to 50 gallons of water will make a mixture, which in most cases will be strong enough to kill plant lice, if thoroughly applied. FoRMULA D.—WHALE-OIL oR FISH-oIL SOAPS. The so-called whale-oil or fish-oil soaps which are quite extensively used for the destruction of plant lice, will usually be effective if thor- oughly applied in the proportion of one-pound of the soap to each six or eight gallons of water. There are numerous brands of these soaps upon the market. Among those that have been used quite successfully are Good’s Whale-Oil Soap and Bowker’s Tree Soap. 2 * * * * * k * * In recent years tobacco extracts have rapidly taken the place of other remedies for aphids, and well informed apple growers are using them almost to the exclusion of other insecticides. It should be remembered that this is a contact: insecticide and kills only the insects actually touched. It is, therefore, necessary to be very thorough in the spraying Fic. 58. Seedling mountain ash photographed June 25, 1913 to show colony of woolly aphids which are the progeny of migrants from elm leaf rosette caged with mountain ash, June 17, 1913. Two apterous generations matured on this seedling, but the third generation proved too much for the little tree which was so nearly dead by August 10 that the last of the aphid colony perished at that time. Fic. 59. Young rosette photographed June 6, 1913. Small picture at right. Fic. 60. Old rosette photographed July 17, 1913. Cc D Fic. 61. Dorsal wax gland of rosette aphid, second generation. A & B,a pair on head. C & D, a pair on prothorax. Notice that the sections are not uniform in number as is often the case. Fics. 62 and 63. Woolly Aphid. Winged and wingless forms. Greatly enlarged. (After Marlatt.) Female. Male. Fics. 64 and 65. Mature sexual individuals of the Wooliy Aphid,—the oviparous female and male. Real size shown in circles at right of figures. (After Alwood.) Fic. 66. Apple root, showing knotty growth caused by Woolly Aphid. Fic. 67. Nymphs of the Woolly Aphid, Schizoneura lanigera on water shoot of mountain ash, Pyrus americana,—the immediate progeny of migrants from elm leaf rosette. Photographed at Orono, June 28, 1912. Enlarged. Fic. 68. Nos. 79-85. Antenne of Woolly Aphid. No. 79—Stem mother from rosette June 5, 1913 (33-13); No. 80—Second genera- tion from rosette June 12, 1913; No. 81—Spring migrant from rosette and progenitor of summer generations on Pyrus (57-13); No. 82— Apterous viviparous form on apple bark (98-08); No. 83—Fall migrant from apple (115-06 ; No. 84—Fall migrant from bred colony on apple; No. 85—Fall migrant from Crataegus.