Historic, archived document Do not assume content reflects current scientific knowledge, policies, or practices. Gniversity of Maine. Mame Aericultural Experiment Station ORONO BULLETIN No. 203 AUGUST, 1912 ELM LEAF CURL AND WOOLLY APPLE APHID. This bulletin contains a report of the migration of the woolly aphid from elm leaf curl to apple, with special reference to the economic significance of this discovery for nursery stock and young orchards. — A general account of this serious and wide spread apple pest is included. MAINE AGRICULTURAL EXPERIMENT STATION ORONO, MAINE. THE STATION COUNCIL. PRESIDENT ROBERT J. ALEY, President DIRECTOR CHARLES D. WOODS, Secretary CHARLES L. JONES, Corinna, FREELAND JONES, LL. B., Bangor, JOHN M. OAK, B. S., Bangor JOHN P. BUCKLEY, Stroudwater, Commissioner of Agriculture Committee of Board of Trustees EUGENE H. LIBBY, Auburn, State Grange ROBERT H. GARDINER, Gardiner, State Pomological Society RUTILLUS ALDEN, Winthrop, State Dairymen’s Association WILLIAM H. DAVIS, Augusta, Maine Livestock Breeders’ Association WILLIAM G. HUNTON, Readfeld, Maine Seed Improvement Association AND THE HEADS AND ASSOCIATES OF STATION DEPARTMENTS. THE. STATION STAFF. 5 CHARLES D. WOODS, Sc. D., Director ADMIN ae : BLANCHE F. POOLER, Clerk and Stenographer TRATION | GEM M. COOMBS, Siennarabher ( RAYMOND PEARL Pay Ds Biologist | MAYNIE R. CURTIS, A. M.,, Assistant BIOLOGY i CLARENCE W. BARBER, B. S., Assistant WALTER ANDERSON, Pouliryman | ESTELLA MORRISON, Computer JAMES M. BARTLETT, M: &., Chemist [gee H. HANSON, M. S., Associate , | ALBERT VERRILL, B. S., Assistant pe SRS : EDWARD E. SAWYER, B.S, Assistant | HELEN W. AVERELL, B. S., Assistant | BARRY C. ALEXANDER, Laboratory Assistant : OSKAR A. JOHANNSEN, Pus. D., Entomologist ENTOMOL- J EpITH M. PATCH, Pu. D., Benede OGY ALICE W. AVERILL, Raboratory, Assistant : WARNER J. MORSE, Pz. D., Pathologist PLANT CHARLES E. LEWIS, Pu. D., eee PATHOLOGY | VERNON FOLSOM, Laboratory Assistant HIGHMOOR WELLINGTON .SINCLAIR, Superintendent FARM GEORGE A. YEATON, Orchardist ROYDEN L. HAMMOND, Seed Analyst and Photographer ELMER R. TOBEY, B. S., Inspector EDGAR WHITE, é Inspector CHARLES S. Be \ Assistani BULLETIN No. 203. PUM EEAr CURL AND WOOLLY APPLE APHID* IByoree: IML) IPAaNerst. The dual personality of certain aphid species is a condition which, before it is detected, betrays the economic entomologist into many futile combative attempts; but on the other hand the same duality may reveal, when once discovered, the most vul- nerable point of attack. It is not necessary to go out of our own state for illustrations. The discovery that Chermes abieti- colens Thomas 1879 which makes cone-like galls on black and red spruce is the same species as Chermes pinifoliae Fitch 1858,** which lays eggs on new growth white pine for progeny that render the pine shoots weakened and unthrifty, gives the landscape gardener his clue. If he treasures the beauty of a group of white pines he would do well to exclude red and black spruces from the vicinity, or conversely if he wishes to grow black spruces with normal branches it is an indiscretion to place them near white pines. Again, when once it was ascertained that the common Alder Blight, Pemphigus tessellata Fitch 1851, was masquerading on the maple (Acer saccharium L.— dasvcarpum Ehrh. and cultivated varieties) as Pemphigus acerifolu Riley 1879,* the owner of ornamental cut leaved maples had a theretofore unstispected means of protecting their foliage by the control of the pest on its alternate food plant, the alder, which in many circumstances is an easy point of control. The economic application of the case in hand is apparently as direct and simple as the two just cited and since we are here concerned with one of the most serious of the apple tree pests, * Papers from the Maine Agricultural Experiment Station: Entomol- ogy No. 58. ** Bulletin 173 Maine Agricultural Experiment Station. + Entomological News, 1908, p. 484; Journal of Economic Entomology 1909, Vol. II, p. 35; Bulletin No. 195 Me. Agr. Exp. Sta., Feb. 13, 1912. SRO oe: rah, 236 MAINE AGRICULTURAL EXPERIMENT STATION. 1012. the significance of the recent discovery * that the elm leaf curl harbors the “wolf in sheep’s clothing” is an important factor to be taken into consideration in dealing with the woolly aphid of the apple. While working over some elm aphides several winters ago I found that I was unable to separate on structural characters certain collections of Schizoneura americana (causing and in- habiting elm leaf curl) from certain collections of Schizoneura lanigera (the troublesome woolly aphid of the apple). Collec- tions could be selected which showed apparently significant antennal differences but others could be selected which could only be separated by reference to the tree from which they had been taken. Notice in this connection antennal figures 449 to 459. (Asa study of the antennal variation in 1,000 individuals of this species is nearly ready for press, further discussion of this point is not necessary here.) This circumstance brought no real conviction, for lanigera (described in 1802) has been under economic surveillance for more than 100 years and Riley (1879) gives descriptions of seven consecutive generations of americana, from the stem mother to the true sexes inclusive, all on the elm. On the other hand spring and return migrants of americana had been re- corded from the widely separated localities of Idaho (Aldrich Ig01), Kansas (Sanborn 1904) and Maine (Patch 1910) and their summer residence was still a mystery. Moreover the overwintering of /anigera on the apple roots was, though con- fusing, no argument against another host for the winter egg, for, as was shown for the Alder Blight, the all year presence of apterous forms on the alder was coincident with a migration to the maple for the deposition of the true sexes and the winter eggs. (Bulletin No. 195 of this Station). Field observations were made during two seasons with this problem in mind but brought no solution, the summer occur- ence of rileyi which I consider to be an elm bark form of americana (See Me. Sta. Bul. 181, p. 237) complicated the situation, while the fact that both hosts were under out door conditions, not easy of control, left too much room for doubt. This past winter, however, material under control conditions was secured by raising seedling apples in the greenhouse where * Science, Vol. 36, p. 30. “Elm Leaf Curl and Woolly Aphid of the Apple.” BEM LBA CURT, AND WOOLLY APPLE APHID. 237 infestation from the woolly aphid was rendered impossible. Leaf curl from elm with pupae and alate forms were secured ‘rom the south some time before material at the same stage would be available here, and migration tests were made. The winged forms from the elm were caged over seedling apples, and their progeny, growing along creases where the thin bark is scaling back, in the axils of the leaves and on exposed roots of the apple seedlings, covered by typical flocculent white secretion, are unmistakably the woolly aphid of the apple. (Fig. 448). The colony in the figure just cited was started May 12-13, by migrants from elm leaf curl. Their progeny thrived from the first and the photograph was taken May 29, the day on which the first apterous generation on the apple began to give birth to young. On part of the seedlings similar tests were unsuccessful, the nymphs dying very soon or in one case after about two weeks tardy growth. This was probably due to aphid resistant seedlings, the ap- ples from which the seeds were planted being from several differ- ent varieties, and as is well known all apples are not alike susceptible to attacks from the woolly aphid. Hapits. 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 Fig. 438. Bark colonies i 3 of Woolly Aphid onapple. conspicuous. (Figs. 438 and 448.) (From Alwood.) On the roots its attacks induce enlargements or galls or swellings, and in the creases of these 238 MAINE AGRICULTURAL EXPERIMEN? STATION. I912. malformations the root ferm occurs in clustere1 masses. The in- jury to the trees is due both to the sucking up and exhaustion of the vital plant juices and to the poisoning of the parts attacked, as indicated by the consequent abnormal growths. Fig. 439. The damage is particularly seri- 4 ous in the case of nursery stock and young trees and is less often impor- tant after the tree has once become well established and of some size. 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 gowth of hard fibrous enlarge- ments with the results in a year or two of the dy- Fig. 439. Crown and root of young apple : - : tree. showing characteristic swellings or ing of the rootlets galls produced by the root lice. (From and their ultimate Alwoed.) decomposition with attendant disappearance of the galls and also of the lice, so that after this stage is reached the cause of the injury is often obscure. On the trunks the presence of the lice results in the roughen- ing of the bark or a granulated condition which is particularly 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 damage above ground, though commonly insignificant, is useful ELM LEAF CURL AND WOOLLY APPLE APHID. 239 as an indication of the probable existence of the lice on the roots. A badly attacked tree assumes a sickly appearance and does not make satisfactory growth, and the leaves become dull and yellowish, 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 lice, not exceeding one-tenth of an inch in length, of a reddish-brown color, and abundantly covered, especially in those above ground, with a flocculent waxy secretion. (Fig. 441.) In autumn, among the wingless ones, winged females, Fig. 440, appear in abundance. They are little, clear-winged, gnat- Fig. 440. Fig. 441. Woolly Aphid. Winged and wingless forms. Greatly enlarged. (From Marlatt.) like objects, greenish-brown, almost ‘black in color, with the body covered with more or less of the cottony secretion. These are the fall or return migrants that seek the elm bark to give birth to the generation of true sexes,—minute wingless, beak- less creatures, the female of which deposits a single ‘‘winter ege’’ within a crevice of the elm bark. On the elm the stem mother, which hatches from the over- wintering eggs sheltered in rough crevices of the bark, appears early. in the spring and may be found in Maine before the mid- dle of May stationed on the partly opened leaf buds. By the last of May the earliest of these wingless stem mothers (Fig. 443) are mature and found in the leaf curl (Fig. 442) or 240 MAINE AGRICULTURAL EXPERIMENT STATION. I912. rosette (Fig. 462, when a group of terminal leaves are affected) which they cause, producing the next generation, which are also wingless. In the summer great numbers of winge! individuals are de- veloped. From the fact that Riley recorded 7 consecutive genera- tions on elm and the occurence of what seems to be the elm bark feeding generations of the same species (known as rileyi) during the summer on tender elm bark, it would seem either that the migration from the elm leaves of these summer migrants Fig. 442. Elm leaf curl, in which the alate spring migrants develop before taking flight to apple bark. is partly to apple bark and partly to elm bark or that elm bark colonies as well as leaf curl may be established by the first or second apterous generations. Such a life cycle is indicated, in the accompanying table. This does not account for the genera- tions resulting from the overwintering forms on the apple roots as their sequence yet remains to be studied. The fall migration of the woolly aphid from apple and the mountain ash I have observed but I have not yet from observation linked it with the true sexes on elm. That inference, however, from the evidence of the spring migration to apple is unmistakable. There are still several important details to be worked out for the woolly aphid of the apple and elm. _ Whether the elm bark BLM LEAF CURL AND WOOLLY APPLE APHID. 241 colonies are originated by the stem mother, or by migrants from the leaf curl or both; whether the mid June (in Maine) winged forms from the elm bark colonies migrate to apple or scatter to other elm bark, or both; the significance of the difference in antennal types of migrants from elm leaf curl (Figs. 451, 452, 454, and 458), whether indicating locality or conditional varia- tion; and complete sequence upon each food plant ;—are subjects for further study. These points can for the most part be watched only with colonies upon seedling stock of the food plants in confinement under such conditions that perfect control of the material can be secured. While I have further work along these lines already under way, some of the problems will need extended observa- tions and it ‘has seemed desirable not to wait until all tangles are straightened out before publishing the main fact. of the migration test from elm leaf curl to apple bark as this point has an important bearing for young trees in nurseries and new orchards and the economic significance of the migration data will not, so far as can be anticipated, be influenced by further detailed study of the different generations. Tur Sprinc Micratrion. The fact of the migration from elm leaf to apple and moun: tain ash under normal out of door conditions was established during the summer of 1912. The migrants from the elm leaves settle on the under side of the apple leaves of water shoots and there produce nymphs which seek the stem at leaf axils and there congregate in woolly masses. The mountain ashes (Pyrius americana and introduced species) are favorite summer hosts in Maine. From one native mountain ash at Orono more than 400 such migrants were removed July 2 to July 12 from the ventral surface of the leaves, and about 150 thriving clusters of woolly aphid nymphs, the immediate progeny of these migrants, were established on the shoots of this single tree.* In this connection it may be of interest to record a forced migfation test. On June 21, t912, | placed several hundred elm *A more detailed account of this occurrence is to be published in the October issue of the Journal of Economic Entomology. 242 MAINE AGRICULTURAI, EXPERIMENT STATION. Igi2. s 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 the 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. SEQUENCE OF GENERATIONS. DESCRIPTIVE. Eqg 0.5 mm. long, gamboge- yellow, inclining to brown in color, with no especial external sculpture. In crevices under elm bark. Stem mother: Pale yellowish- red, with black members when first hatched; the red deepening and becoming purplish or livid with age. When mature, aver- aging 3.5 mm. in length, globose or pyriform, with subobsolete Fig. 443. Stem mother. honey-tubes and six dorsal rows (Brom! Riley) of darker piliferous and tuber- culous spots. Antenna 5-jointed, joint 3 more than equaling 4 and 5 together in length. Causing and inhabiting elm leaf curl. Second generation. Apterous viviparous forms which do not become so large as the stem mother. The antenna is normally 6-jointed (Fig. 461). Inhabiting leaf curl and giving birth to migrants. Third generation. Winged viviparous female: Body dusky, the abdomen slightly reddish; legs either dusky or yellowish red. Antenne as long as head and thorax together, dusky, rarely yellowish, not pilose, but with a few short setous points; 6-jointed. The annulation of the joints in-different collections and from different localities varies greatly. Figs 451, 452, 454. ELM LBAE CURL AND WOOLLY APPLE APHID. 243, and 458, cover the ordinary range. The absolute size of this generation is subject to considerable variation. These develop within and mi- erate from the elm leaf curl, and settling on apple produce young which inhabit ap- ple. Fourth genera- ton. That from the first winged females: Differs from the preced- Fig. 444. © Third generation. oS toate, es (From Riley.) muscis being much longer. The antenne have 6 joints, with no annulated constrictions. The color is sometimes decidedly orange. When newly hatched, the thickened end of the promuscis often extends one-half the length of the body beyond caudal extremity. It is born with an enveloping pellicle or pseudovum, and though of a bright red with pale legs at first soon becomes brownish, with dark mem- bers. Deposited on apple by the spring migrants and developing there in flocculent masses. Fig. 448. When mature, if the colony is crowded, some of the individuals move to a new cite on the apple bark before giving birth to the nymphs which settle near and establish thus new colonies. In other cases the nymphs themselves scatter to new cites. Fifth generation. ‘The second apterous generation on apple bark. Practically like the fourth generation. Sixth? generation. From about the first of September until frost the winged fall migrants develop in the woolly colonies on apple, mountain ash, and Crataegus whence they migrate to elm bark to deposit their progeny, the true sexes. Figs. 455, 450, 457 and 459 give the antenne of the fall migrant. Together with these in the same woolly colonies develop apterous viviparous females that give birth to nymphs which seek the roots of the trees and hibernate there, surviving the winter if the conditions are favorable. 244 MAINE AGRICULTURAL EXPERIMENT STATION. IQ12. True sexual individuals: Born within an egg-like pellicle; the antenne 5-jointed, with the jcints subequal. Orange in color. Undergoing one molt, and then being at once distinguished from the other forms by the brighter orange-yellow color, the rudi- mentary mouth, the more simple eyes (composed of three facets), by the shorter, 5-jointed antennz, the joints subequal in length, by the shorter legs, with smaller claws to the tarsi,’ and more distinct terminal capitate hairs or pulvilli. The skin is transparent, the body filled more or less with fatty globules. The female is nearly pyriform, and averages 0.4 mm. in length. A single egg is visible through the translucent skin and occupies nearly the whole of the body. The male is narrower and smaller. Figs. 446 and 447. This generation seems to have no object in life except the deposition of eggs, since they can not eat or fly. The eggs are placed in the deepest crevices of the bark, especially those that are tangential to the tree, and are not easy to find. The small lice perish after depositing eggs leaving only the latter to sur- vive the winter. Economic STATUS.* The danger from the woolly aphid is greatest to nursery stock and young orchards. Mr. Marlatt (Journal of Economic Ento- mology, Vol. 4. pp. 116-117) in recording the use of American- grown apple seedlings says:—“Mr. F. W. Watson, of Topeka, *“NMr. W. S. Griesa, proprietor of Mt. Hope Nurseries, Lawrence, Kan., has established the Griesa Research Fellowship in Entomology in memory of his father, the late A. C. Griesa. In establishing this fel- lowship it was the wish of the founder that the holder should devote himself to a fundamental investigation of one of the several entomolo- gical problems ever present with nurserymen. “Upon consultation, it was decided to select for the theme of this research the Woolly Aphis. Mr. H. W. Lohrenz, A. B., McPherson College, and a graduate student at the University of Kansas, was elected by the regents of the university to this fellowship. “The purpose of this research is, after careful experimentation in remedy and prevention, and investigation into the life cycle of this Aphis, to devise a practical means whereby nurserymen can properly deal with this economic problem in such a way as to eliminate the losses now attending the existence of this insect on nursery stock. * * * * * XS * * * “Tt is worthy of note as showing the interest of nurserymen generally in foundations of this nature that the Western Nurserymen’s Associa- tion, an organization of nurserymen of the Middle Western States, passed resolutions commending the founder of this fellowship for the ge he has instituted.’ Journal of Economic Entomology. Vol. 4, p. 161. > BLM LEAF CURL ‘AND WOOLLY APPLE APHID. 245 Kans., in an article in the National Nurseryman for January, 1910, 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 production 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 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. Fig. 445. Fore wing of migrant from elm leaf curl to apple. Third Generation. 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 Commis- sion in his excellent account of this insect states “On nursery stock the woolly aphis is a most sertous 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 246 MAINE AGRICULTURAL EXPERIMENT STATION. IQ12. doubtful whether the codling moth, or the woolly aphis, 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 cf what has already been said. That the elm leaf curl renders the foliage of this stately tree unsightly during years of heavy infestations is well enough known in all parts of the country where the American elm is grown. Professor Gillette (Journ. Ec. Ent. Vol. 2, p. 356) Female. Mate. Fig. 446 and Fig. 447. Mature sexual individuals of the Woolly Aphid—the oviparous female and male. (From Alwood. states of this insect——‘This louse is a real pest upon white elm nearly everywhere that this tree is grown in Colorado.” In Montana where the white elm (U/mus americana) is being established as a shade tree the insects of the elm leaf curl have taken up their- abode but have found no cordial welcome for Professor Cooley says of them (Cooley 1904, p. 44). “Altogether they are a decidedly obnoxious pest. Not only do they distinctly injure the trees but they disfigure them as well and furnish an attraction for ants, flies and other insects which visit them for the sweet liquid.” BEM LEAR CURL AND WOOLLY APPLE APHID. ZAG; Pipe CviCLEY OF WOOLEY APHID, OF APPLE. ERLM: Primary Host. EGGS. (Under bark all winter) STE M-MOTHER. (first generation in leaf curl. Apterous viviparous females). SECOND GENERATION. (apterous viviparous females in leaf curl). SPRING MIGRANTS Migrate to apple (third generation. SUMMER GENERATIONS. ON ELM BARK. Migrate to elm <—_. Alate viviparous parthenogenetic females, Sept.-Oct. APTEROUS OVIPAROUS FEMALES AND APTEROUS MALES. EGGS. (under bark all winter). Alate viviparous). FALL MIGRANTS. APPLE: Alternate Host. NYMPHS. (From hibernating forms on roots, etc.) migrating to trunk or branches in early spring. SEVERAL GENERATIONS.. FOURTH GENERATION. (apterous viviparous females). FIFTH GENERATION. (apterous viviparous females). APTEROUS VIVIPAROUS: PARTHENOGENETIC FEMALES, mature in Sept.-Oct. mature sexuparae, HIBERNATING FORMS ON APPLE ROOT. 248 MAINE AGRICULTURAL EXPERIMENT STATION. IQ12- 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 knowledge that the source of danger lies in the migrants from the pre- viously unsuspected elm curl, it is seen to be possible to control 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 practi- cable. 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 thorough- ness to penetrate the covering and protecting cottony secretion. If the wash be applied warm, its penetration will be consider- ably: increased. ELM LEA CURI, AND WOOLLY APPLE APHID. 249 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 aphides removed. 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. Formuta A—Tosacco DEcocTION. ihobaccoustems= or tobacco! dust: asec... ssces-- 2 pounds WAVEMNCTE: = aig oe crerocc e ae uT REECE ce Sc Caer hr ae 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 of tobacco to each four gallons of water. No lime or 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 “Nikoteew’ 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. Nikoteen 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 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 stfficient 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 gallon to each one hundred gallons of water. Thoroughness of application is of as much importance as the strength of the material used. 250 MAINE AGRICULTURAL EXPERIMENT STATION. IG12- Nikoteen is a more concentrated abstract, I 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 700 or 900 parts of water. It is the common practice to add soap,—whale oil soap or zoed laun- 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 ae a little lime instead of soap, the inert solid in suspension aiding the extract to “wet” and “stick” to the bodies of the aphides. For this purpose 1 pound of stone lime, slaked and strained into 50 gallons of tobacco extract as prepared for application, is sufficient. ForMULA B.—KEROSENE EMULSION. lard ® Soap Saas eece eo cists ot reel eet ee I-2 pound Boiling: (Witenes accnt seen Setar eee eee I gallon Kerosene: 26 $s Scenes cee sates Siete eee 2 gallons To prepare, dissolve one-half pound of soap in one gallon of soit 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 forcefully 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 top. In such cases, if the last in the barrel or tank is pumped out upon the 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. ; FormtuLta C—Miscrsre Ors. There are several miscible oils upgn 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” ELM LEAF CURL AND WOOLLY APPLE APHID. 251 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. FormuLta D.—WHALE-oll, OR FISH-orL, 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. In recent years tobacco extracts have rapidly taken the place of other remedies for aphides, 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. i) 252 MAINE AGRICULTURAL, EXPERIMENT STATION. IQ12. InsEct ENEMIES OF THE WooL_Ly APHID. So far as the natural enemies of this pest are concerned its residence in the elm leaf curl is a vulnerable period strongly sub- ject to attack. Very abundant in Maine working on the aphides while in the elm leaf curl are a predaceous capsid, (Campto- brochis nitens), flocculent larve of a Coccinellid and syrphus maggots. So numerous are all these insects in certain years that it has sometimes been difficult for me to secure enough of this aphid for experimental purposes——a search through many ‘emptied leaf curls being necessary before aphides could be found. In other parts of the country also this.aphid is preyed upon while in the elm leaf curl and frequently the only living arrivals in material sent me from other states has been the predaceous insects within the leaf curl. Riley (1879) records as follows:—“Among the more promi- nent of the natural enemies of this species I have noticed, of Coleoptera, Coccinella 9-notata, Coccinella sanguinea (munda) Say, Hippodamia convergens, and several species of Scymnus. I also found feeding upon them the perfect beetle of Podabrus modestus, and the Hemipierous Cyliocoris scutellatus Ubhler, and Capsus linearis Beauv. A Lepidopterous inquiline, name- ly, the larva of Semasia prunivora Walsh is also quite common within the curled leaves, feeding both on the lice and on the substance of the leaf. A large green Syrphus larva and several Chrysopa larve also prey upon them.” While on the apples the woolly aphid is subject to the attacks of a number of insect enemies, those recorded by Marlatt (1897) including “the parasitic chalcis fly, Aphelinus mali Haldemann, and the larva of a syrphus fly, Pipiza radicum Walsh and Riley, and also the larva and adult of several species of lady birds, the larve of lace-wing flies, and spiders, etc. In the East a very small brown species of ladybird, Scymnus cervicalis Muls., is often present in some numbers, and the common nine-spotted ladybird, Coccinella 9-notata Hbst., is also an active enemy of the woolly aphid. BRAD LEA (URI, AND WOOLLY APPLE APTI: 253 “The most active natural enemies of the woolly aphis in Colorado have been predaceous insects. We have reared no parasite from it, but, Aug. 21, 1908, Mr. L. C. Bragg brought into my office a female Aphelinus mali busily ovipositing in apterous females of this louse. Among the Coccinellids, Hip- podamia convergens is by far the most abundant destroyer of this louse both upon the eastern and western slopes of the mountains. Mr. E. P. Taylor also took AH. sinuata, Coccinella g-notata, C. monticola and C. transversalis feeding on this louse in the orchards about Grand Junction, and we have noted H. transveralis, C 9-notata, C. monticoia, C frigida, and C. 5- notata (transversalis and transversoguttata) feeding upon it in eastern Colorado. — “Mr. Taylor also reared two syrphus flies at Grand Junction on this louse, namely, Catabomba pyrastri Linn, and Eupeodes volucris O. S. “Lace-wing flies are also very destructive to Schizoneura lemgera in Colorado, and especially upon the western slope in the Grand Valley, where Mr. Taylor concluded that they did more than all else to subdue the unusually severe outbreak of this louse in that valley during the early summer of 1907. The Capsid, Camptobrochus nebulosus Uhl, we have found a com- mon feeder upon this and some other plant lice in Colorado.” (Gillette 1908). Foop PLAN’s. Crataegus Crus-galli (lucida). Schizoneura crataegi Oestlund. Davis, IQIO, p. 412. Crataegus punctata Jacq. Schizoneura crataegi Oestlund. Oestlund, 1887, p. 28. (Now considered lanigera by Professor Oest- lund). Crataegus tomentosus L. Schizonewra crataegi Oestlund. Williams, IQIO, p. 20. Crataegus sp. Schizoneura lanigera. Patch, 1912a, p. 236. Pyrus malus L. Schizoneura lanigera Hausmann. Alwood, 1904. Gil- lette and Taylor, 1908, p. 28. Pyrus -gitchensis. Schizoneura lanigera. Patch, 1912a, p. 236. (Also on two other cultivated species of mountain ash). Ulmus americana L. Schizoneura americana. Riley and Schizoneura rileyi Thomas (Eriesoma ulmi Riley). Patch, 1910a. Wil- liams, IQro. 254 MAINE AGRICULTURAL EXPERIMENT STATION. I912. Ulmus campestris L. Schizoneura ulmi L. (americana Riley). Gillette, 1909. p. 356. * * o* * % % * * * * * * *% *% * * * * * * x * Ulmus campestris L. Schizoneura ulsmt (Linn). (A. foliorum De Geer) (S. americana Riley?) Buckton, Vol. 3, pp. 98, 100. Ulmus sp. Schizoneura ulni Linn (fodiens Buckton) Tullgren, 1900. 7 p. 169. Ribes sp. Schizoneura ulmi Linn. (fodiens Buckton) Tullgren, 1909, p. 1609. ELAL LEAR CURL AND WOOLLYs APPLE APITID: 255 SYNONYMY AND LITERATURE. A complete bibliography for this species is not desirable here as the accounts which throw original light upon the life his- tory would be lost in a mass of publications compiled for eco- nomic purposes. 1802. Aphis lanigera, Hausmann, Beitrage zu den materialien fur eine kunftige Bearbeitung der Blattlause. Illigers Magazine. T. I. Coccus mali. Bingley (Thomas 1879, p. 126). Eriosoma mali. (Leach MSS.) Samouelle. (Lhomas, 1879, p. 126). Myzoxylus mali. Blot. (Thomas, 1879, p. 126). 1841. Eriosoma (Aphis) lanigera, Harris. Report on the Insects of of Mass. injurious to vegetation, p. 193. 1841. Schizoneura lanigera, Hartig, Germar’s Zeit. Ent. III, p.-359. 1851. Eriosoma pyri, Fitch. Fourth Report of the N. Y. State Cabinet of Nat. Hist. A. D. 1851, p. 68. 1856. Pemphigus pyri. Fitch. First Report on the Noxious, Beneficial and other Insects of the State of New York, p. 5. An account of the work upon the roots and a description of the young nymph and winged individuals, the latter evidently either with abnormal venation or an accidental migrant of a different species as this form is described with the venation of a Pem- phigus. 1858. Pemphigus americanus? Walker. List of the specimens of Homopterous Insects in the collection of the British Museum. 1862. Eriosoma (Aphis) lanigera, Harris. Insects Injurious to Vege- tation, p. 242. 1869. Eriosoma (Pemphigus) pyri, Riley. Insects of Missouri I, p. 118. Economic account of work on apple roots. 1869. Eriosoma ulmi, Riley. Insects of Missouri I, p. 123. Descrip- tion of winged forms and nymphs, and account of work on elm bark. 1879. Schizoneura americana, Riley. Bul. U. S. Geol. and Geograph. Survey, Vol. V, No. 1, pp. 4-9 and Plate T and Fig. 2. Descrip- tion of seven generations on elm, with an account of the work on elm. 1879. Schizonevra americana, Thomas, (III), Report of the State Entomologist Il]. VIII, p. 202. Quotes Riley’s description of seven generations, and concludes (p. 204): “This as admitted by Professor Riley is very closely allied to Schizoneura ulmi,