New Jersey Agricultural Experiment Stations SB 9^45 A5H43 bulletin 328 1918 ENT ^^sm/'^/W 1 ^^ \^jl/M wT v 4 ^^H % «/ f" ^''^Pv i i at Sprayed Unsprayed Effect of proper spraying SOME important ORCHARD PLANT LICE New Brunswick, N. J. New Jersey Agricultural Experiment Stations SB A5H^3 1918 ENT BULLETIN 328 Sprayed Unsprayed Effect of proper spraying SOME IMPORTANT ORCHARD PLANT LICE New Brunswick, N. J. NEW JERSEY AQRICULTURAL EXPERIMENT STATIONS NEW BRUNSWICK, N. J. STATE STATION. ESTABLISHED 1880. BOARD OF MANAGERS. His Excellency WALTER E. EDGE, LL.D Trenton, Governor of the State of New Jersey. W. H. S. DEMAREST, D.D New Brunswick, President of the State Agricultural College. JACOB G. LIPMAN, Ph.D Professor of Agriculture of the State Agricultural College. Name Address County ^^'illiam A. Blair Elwood JNIiddlese.x Arthur Lozier Ridgewood Monmouth R. R. Lippincott Vincentown Morns Ephraim T. Gill Haddontield Ocean . ^^ ...„^ Charles X'anaman Dias Creek Passaic Cumberland Charles F. Seabrook Rridgeton Salem Essex Zenos G. Crane Caldwell Somerset Gloucester Wilbur Beckett Swede.sboro Sussex Hudson niedrich Bahrenburg Union Hill Union Hunterdon Egbert T. Bush Stockton Warren Mercer Josiah T. AUinson Yardville County Atlantic Bergen Burlington Camden Cape May A'a;j!c' Tames Neilson William H. Reid John C. Welsh Joseph Sapp Isaac A. Servcn Charles R. Hires Joseph Laroctjuc- Robert \^ .'\rmstronj John Z. Hatfield James I. Cooke Address New Bruns'k Tenncnt Ger'n \ alley Tuckerton Clifton Salem Bcrnardsville Augusta Scotch Plains Delaware STAFF. Jacob G. Lipman, Ph.D.... Frank G. Helyar, B.Sc... Irvi.ng E. Quackenboss. . . Carl R. Woodward, B.Sc. Hazel H. Moran . Director. .Associate in Station Administration. .Chief Clerk, Secretary and Treasurer. .Editor. .Assistant Librarian. Frank App, B.Sc Agronomist. Irving L. Owen, B.Sc. . .Associate Agronomist. J. Marshall Hunter, B.Sc, Animal Hushandmaii. Charles S. Cathcart, M.Sc Chemist. Ralph L. Willis, B.Sc Assistant Chemist. Archie C. Wark Laboratory Assistant. W. Andrew Cray Sampler and Assistant. Harry C. McLean, Ph.D. .Chemist Soil Res'h. William M. Regan, A.M. .Dairy Husbandman. Willes B. Co.mbs, A.m., Assistant Dairy Husbandmaii Thomas J. Headlee, Ph.D Entomologist. Chas. S. Beckwith, B.Sc, Asst. Entomologist. Mitchell Carroll, B.Sc, Asst. Entomologist. Maurice A. Blake, B.Sc Horticulturist. Vincent J. Breazeale, Foreman, Vegetable Growing. Charles H. Connors, B.Sc, Assistant in Experimental Horticulture. .Arthur J. Farley, B.Sc, Specialist in Fruit Studies. William Sciheferstein, ..Orchard Foreman. Lyman G. Schermeriiorn. B.Sc, Specialist in Vegetable Studies. H. j\I. Biekart Florist. Harry R. Lewis, M.Agr., Poultry Husbandman. Ralston R. Han n as, B.Sc, .Assistant in Poultry Research. Morris SiEGEL Poultry Foreman. El.mer H. Wene Poultry Foreman. JoH.N P. Helyar, M.Sc Seed Analyst. Jessie G. Fiske, Ph.B. . . . Asst. Seed Analyst. AGRICULTURAL COLLEGE STATION. ESTABLISHED 1888. BOARD OF CONTROL. The Board of Trustees of Rutgers College in New Jersey. EXECUTIVE COMMITTEE OF THE BOARD. W. H. S. DEM.AREST, D.D., President of Rutgers College, Chairman New Brunswick. WILLIAM H. LEUPP New Brunswick. JAMES NEILSON New Brunswick. WILLIAM S. MYERS New York City. JOSEPH S. FRELINGHUYSEN Raritan. J. AMORY HASKELL, Red Bank. STAFF. J.ACOB G. LIPMAN, Ph.D Director. HENRY P. SCHNEEWEISS, A.B. Chief Clerk. Byron D. Halsted. Sc.D Botanist. .Augusta E. Mesi:e. ... Stenographer and Clerk. John W. Shive, Ph.D. .. .Plant Physiologist. Melville T. Cook, Ph.D. ... Plant Pathologist. Earle J. Owen, M.Sc. .. .Assistant in Botany. Jacob G. Lipman, Ph.D., Frederick W. Roberts, A.M., Soil Chemist and Bacteriologist. Assistant in Plant Breeding. Augustine W. Blair, A.M., Mathilde Groth Laboratory Aid. .Associate Soil Chemist. Thomas J. Headlee, Ph.D Entomologist. Cyrus Witmer. Field and Laboratory Assistant. Alvah Peterson, Ph.D Asst. Entomologist. Staff list revised to June 30, 1918. NEW JERSEY STATE AGRICULTURAL EXPERIMENT STATION DEPARTMENT OF AGRICULTURAL EXTENSION ORGANIZED 1912 AND NEW JERSEY STATE AGRICULTURAL COLLEGE DIVISION OF EXTENSION IN AGRICULTURE AND HOME ECONOMICS ORGANIZED 1914 Alva Agee, M.Sc., Director and State Superin- tendent of County Demonstration. Frank App, B.Sc, Acting State Leader of Farm Demonstration.. Victor G. Aubry, B.Sc, Specialist, Poultry Husbandry. John \V. Bartlett, B.Sc, Specialist, Dairy Husbandry. RoscoE W. DeBaun, B.Sc, Specialist, Market Gardening. J. B. R. Dickey, B.Sc, Specialist, Soil Fertility and Agronomy. William B. Duryee, B.Sc, Specialist, Farm Management. Marjory Eells, D.S., Home Demonstration Agent. Ed.n'a Gulick, Home Demonstration Agent. William H. Hamilton, B.Sc, Assistant State Leader of County Demonstration. M. Anna Hauser, B.Sc, Home Demonstratioo Leader. Arthur M. Hulbert, State Leader of Boys'' and Girls' Club Work. Sara T. Jackson, B.S., Assistant State Club Leader. Nelle Johnson, M.A., Assistant Home Dem- onstration Leader. Ethel Jones, M.A., Asst. State Club Leader. William F. Knowles, A.B., Assistant State Club Leader. William M. McIntyre, Assistant Specialist, Fruit Growing. Helen E- Minch, Specialist, Home Economics. Charles H. Nissley, B.Sc, Specialist, Fruit and Vegetable Growing. Carl R. Woodward, B.Sc, Editor. Paul B. Bennetch, B.Sc, Demonstrator for Sussex County. Frank A. Carroll, Demonstrator for Mercer County. Elwood L. Chase, B.Sc, Demonstrator for Gloucester County. Bertha Cold, B.Sc, Home Demonstratioii Agent for Jersey City. Louis A. Cooley, B.Sc, Demonstration Agent for Ocean County. Herbert R. Cox, M.S. A., Demonstration Ageni for Camden County. Josephine C. Cramer, Home Demonstration Agent for Middlesex County. Lee W. Crittenden, B.Sc, Demonstrator for Middlesex County. Ellwood Douglass, Demonstrator for Mon- mouth County. Irvin T. Francis, A.B., Demonstration Agent for Essex County. Harry C. Haines, Demonstration Agent foi Somerset County. Margaret H. Hartnett, Home Demonstration Agent for Paterson. William A. Houston, Assistant Demonstration Agent for Sussex County. Lauretta P. James, B.Sc, Home Demonstra- tion Agent for Mercer County. Philip F. Keil, Demonstration Agent for Bur- lington County. Harvev S. LiPPiNCOTT, B.Agr., Demonstrator for Morris County. L. F. Merrill, B.Sc, Demonstrator for Ber- gen County. Adelia F. Xoble, Home Demonstration Agent for Princeton. Warren W. Oley, B.Sc, Demonstrator for Cumberland County. Ethel Osmond, B.Sc, Home Demonstration Agent. Lena R. Pierce. B.Sc, Llome Demonstration Agent for Trenton. REGINE i'orges, B.Sc, Home Demonstration Agent for Passaic. Caroline R. Simons, Home Demonstratioi. Agent for Camden. James A. Stackhouse, B.Sc, Demonstrator for Cape May County. Eunice Straw, B.Sc, Home Demonstration Agent for Monmouth County. Walter C. Vail, B.Sc, Demonstrator for Salem County. Louisa VanuxEm, Home Demonstration Agent for Newark. XoRiNE Webster, Home Demonstration Agent for Bayonne. Harold E. Wettyen, B.Sc, Demonstration Agent for Passaic County. Carolyn F. WetzEl, Home Demonstration Agent for Bergen County. .\lbert E. Wilkinson, M.Agr., Demonstration Agent for Atlantic County. CONTENTS Introduction 5 Recognition Marks 6 Nature and Extent of Injur.v 8 Life History and Habits lo Control 13 Determining Whetiier Control ^Measures are Necessary 13 The Problem 13 Destroying the Aphis in the Fall 14 Destroying the Aphis in the Egg Stage 14 Destroying the Aphis in the Spring and Sinnmer 15 Conclusions 26 ILLUSTRATIONS Effect of proper si.Mayint;, Cover First stage of the green, tlie rosy and the oat aphis 6 Injury to foliage 8 Injury to fruit 9 Trees not properly sprayed for aphis 22 Trees properly sprayed for aphis 23 Stages in bud development 25 Fig. I Fig. 2. Fig. 3- Fig. 4- Fig. 5- Fig. 6. (4) New Jersey Agricultural Experiment Stations BULLETIN 328 FEBRUARY 15, 1918 / Some Important Orchard Plant Lice BY Thomas J. Hkadlhi;, Ph.D. In zvinter. small {i/jO of an inch long) shining-black oTal eggs on the roughened places or close to the buds of the small tender twigs of the apple tree: in spring and early summer, small variously colored lice congregated on the undersides of the leaves causing them to curl up, die, and fall off, dwarfing the fruit and sometimes ruining the crop. Introduction Four species of plant lice are usiialh- listed as commonly rittacking the foliage and to some extent the fruit of the apple tree. All winter in the egg stage on the smaller loranches and twigs of the trees. All hatch from the eggs and develop one or more generations on the tree. .\11 except one — the green apple aphi.s — migrate from the apple to other plants. All return to the apple either the first or second fall following and lay the over-wintering eggs. The species concerned are the green 'ipple aphis (Aphis pomi DeG. ), the rosy apple aphis (Aphis sorbi Kalt. ), the oat aphis iSiphocoryne aveme Fah. ) and the clover aphis (ApJiis bakeri CoAvsen). In New Jersey the clover aphis has not hecn recorded. L'nlil two years ago the green apple aphis was the onK s])ecics re- garded as a pest. In the season of 1015 the ro^\- a])ple aphis appeared in large numbers in almost all parts of the state and (5) 6 Bulletin 32S did much damage. The faihire of the usual methods of aphis control when this species appeared necessitated a study of the problem, and in the follovx'ing account it is attempted to set forth the most important of the results obtained. Recognition Marks The stage in which the aphis is found throughout the winter and early spring is a small shining-black egg fastened to the bark of the twigs and smaller branches. They are likely to be laid on the tender ends of water sprouts, in the depressions about bud and pruning scars, or partly or completely inserted ])etween the buds and the stem. The eggs of green apple aphis have in our experience been more commonly found on the water sprouts than those of either of the other species. Fig. I. First stage of the green, the rosy and the oat aphis (After Parrott, Hodgkiss and Lathrop) The newly-hatched lice of the green, the rosy, and the oat aphis are very small, dark-green in color and look much alike. Parrott, Hodgekiss, and Lathrop^ have discovered differences by which one species may be told from another, and Dr. Alvah Peterson has found that the characters cited by them hc^ld for New Jersey conditions. The length of the antennas, or feelers, and the size and shape of the cornicles, or honey tubes, are the points that we have found most useful in distinguishing the dift'erent species. As these young develop into wingless stem-mothers, their characteristic differences become so distinct that recognition of 'Parrott, P. J., Hodgekiss, H. E., and Lathrop, F. H., 1917. Phintlice injurious to apple orchards. II. Studies on control of newly-hatched aphides. N. Y. (Geneva) Agr. Exp. Sta. Bui. 43i- Some Important Orchard Plant Lice i-t \'cry dark ^ re o ■5 S o re >r OJ ^ > 5= - - o >> 1 c o V3 S S n -0 5< c S" «i OJ ■" bo 3 > rt 9 c S Sis S"" -^^ bo ~ OM-. bc" 2 ^ ^ « J ^'^ lis: bi^^ .s ° r "^ 1! re -a « 6 V u IS II li u 're a. 1^ re 3 _j- « 1 ^ ? -^ re C "3 O o u -a _>> o J; nl :5 > & -c .«^ c s S 2-3 a «.^ c >. j:~ o « „ !" 1- '■'' 0-- r- D ^ 5 c 1- bi) 1 re ij a >. 1 D. t/5 o re o 8 Bulletin 328 the species Ijecomes eas}'. The aduk stem-mother of the oat aphis is pale yellowish green, with a darker streak along the mid- dle line of the back, while that of the green apple aphis is bright green, and that of the rosy aphis has a slaty cast and is covered with powder. Nature and Extent of Injury As soon as each species hatches from the egg it attacks such of the young unfolding foliage as may be out. It works its mouth parts through the rind of the plant and sucks out the sap. As the liower Ijuds are exposed by the development of the tree, thc\' in turn are attacked. Fit liiiur\' tn foliage The wounding of the tissue and the withdrawal of sap upsets the rate of growth of the part attacked in such a fashion as to cause curling of foliage and distortion of the fruit. The activitv of the oat aphis causes little curling of the foliage, and as the second l)rood develops wings and leaves the tree by the time the fruit has well set, the troul)le is soon past. To what extent the feeding on the Inids and tiower clusters may so weaken them as to ])revent setting, we do not know, 1)ut it is possible that such an injury takes place. Some Important Orchard Plant Lice 9 The green apple aphis, hke the preceding species, causes Httle curHng of the fohage at the Ijeginning of the season. Later its activity resuhs in the most pronounced curhng. The rosy apple aphis, on the other hand, produces much curl- ing of the foliage, probably Ijecause it devotes its attention more exclusively to the leaves. Ijoth the green apple aphis and the rosy, especially the latter, have done very serious injury to fruit, causing it to be knotted and gnarled and never to reach a salal)le size. Recently it has been shown that plant lice can and do spread fire l)light.- It is thought that such of them as hatch from eggs which were laid in Ijlight cankers may carry the blight germ to other parts of the tree. Fig. 3. Injury to fruit The extent of the injury depends upon the abundance of the lice. When very plentiful the tree mav l)e almost defoliated and the crop utterly ruined. In 191 5 the injury was general throughout the state and orchards everywhere showed the work of plant lice. The season of 19 16 showed a smaller amount of 'Merrill, J. H., IQ17. Further data on ihc relation of aphides and fire hlisht ( Bacillius aiiiyloronis ) . In jour. Ivcon. luit., v. 10, p. 45-47. lo Bulletin 328 injury, and there was an epidemic of fire blight. As seen by the writer, there is no necessary connection between the epidemic and the aphis, l)ecause the aphis was worse in 1915 and 191 7 than in 19 16, while the fire blight was limited in these two years. In 191 5 Mr. John Barclay, of Cranbury, estimated the damage done his orchard l)y apple aphis at $40 an acre. This occurred in spite of the practice of w^hat was then thought to be careful spraying for the insects. Life History and Habits All species pass the winter in the egg stage attached to the l)ark of the twigs and smaller branches of the trees. The green apple aphis appears to be partial to water sprouts, while the eggs of the other species are likely to be found in depressions about pruning, bud and fruit scars, or thrust almost or quite out of sight between the bud and stem. The oat aphis w^as the first species to hatch at New Brunswick and vicinity in the spring of 19 17. They w^re discovered on the buds on March 31. Then (about April 12 to 14) came the rosy aphis and green apple aphis almost coincidently. The dif- ference in the time of hatching of the first two species was suf- ficiently great for the oat aphis to have hatched and reached the buds, and to have been destroyed by insecticides, while the rosy, at that time in the egg stage, hatched later and seriously dam- aged the foliage. The oat aphis reached the buds as they were swelling and before any leaves were yet projecting, while the rosy came on only after the tiny leaves w^re projecting from forward buds like squirrel ears. The rosy aphis hatched at the same stage of bud development as in 191 6. Inasmuch as the experience rela- tive to time when the rosy aphis hatches differs in different parts of the country, the writer will quote from his notes in 1916: "Early in the forenoon Mr. Barclay called me over the telephone and told me that the aphis began emerging in his orchard in enormous numbers on the preceding afternoon (April 15, 1916). The day was clear and warm and the personal examination, which I made later in the morning, showed aphis present every- where in large numbers. Nearly every flower bud on unsprayed trees showed at least one-half dozen specimens, while the buds on trees treated with 'Scalecide' or with winter-strength lime-sulfur in dormancy rarely exhibited more than one specimen to the bud. * * '■'''- At this time the most advanced cluster buds showed the first green leaves separating from the cluster, and the young leaves projecting from the opening l)uds like squirrel ears were Som;-: I:\rr()R'i.\xT Orchard Plant Lick ii very common everywhere throughout the orchard." It is thus seen that for two years in the Barclay orchard, the rosy aphis hatched after the leaves began to emerge from the buds and at a time when shelter from spraying materials could be had. The second generation of the oat aphis developes wings and migrates from the apple to various grasses (species of Poa). Here they breed throughout the summer. It is thought that they pass the winter on grains and grasses and do not return to the apple until the second fall. At any rate, in the fall ( late September or early October) winged forms of this species begin to appear on the apple, males and females are produced, and fertilized eggs are laid on the tree. Egg-laying may continue until December. The species mav l)e found la}'ing eggs on pear, ([uince, haw- thorne, and plum trees. The third generation of the rosy aphis is winged and migrates from the trees about the middle of June to plantains, where it remains throughout the summer, returning to the apple in late October and earlv X^ovember. ]\Iales and females are produced bv the returned migrants and fertilized eggs are laid to pass the winter. The green apple aphis lives on the apple, pear, ([uince, and hawthorne, especially the first, throughout the summer. The winged forms seem merely to spread the species to other parts of the tree or to other trees. In the fall (October) males and females are produced and fertilized eggs are laid for winter. \\'hen the eggs are first laid they are yellowish in color and gradually become darker until they assume the normal shining- black appearance. It thus appears that the apple suffers from the oat and the rosy aphis during the early stages of fruit production onl) ; the former leaving when the apples are just well set and the other in June. The green aphis, on the other hand, is on the trees continuously throughout the season. Perhaps the most puzzling phase of the aphis problem is the fact that the plant lice are bad one year and hardly noticeable the next. The explanation for this puzzle appears to lie in the eft'ect of the weather upon the aphids and their natural enemies. The natural enemies of apple plant lice may be placed in i\\ ^ general groups — the parasitic enemies, which usually lay their eggs inside the body of the aphid, from which comes a grub that eventually destroyes the aphid, and the predaceous enemies, that attack, kill and consume the lice. The principal members of the first group belong to the / 1 yiiiriin/'tcra. or the group of bees, ants and wasps. These parasitic forms are usually very small and very greatly influenced by weather conditions. 12 Bulletin 328 The elements of climate which, because of their large varia- tions, influence insect life to a great extent, are temperature and .moisture, especially the former. It is therefore, to be expected that if weather has anything to do with the matter, temperature and moisture must be playing a large part. Perhaps the influence of these factors upon the relation existing between the plant lice and their natural enemies has been best illustrated by a study of Lysiphelbus tritici, a small hymenopterous (the order which in- cludes the bees, ants and wasps) parasite of Toxoptcra grauii- num, one of the most injurious of the plant lice attacking wheat and oats. Under a constant temperature of 50" F. and an atmospheric moisture ranging from "j^ to 100 per cent, 43 days were required for the parasite to develop from egg to adult. Furthermore, at this temperature, the number of healthy young produced is gieatly reduced, in fact the insect hardly reproduces itself. On the other hand, under a temperature of 50° F. and the same atmospheric moisture the louse requires 24 days from birth to maturity and reproduces, once that stage has been reached, nearly one young a day for 2"/ days. At a temperature of 70 F. the parasite can complete its life cycle in 10 days, and the average number of young ones from a single pair of parents amounts to 56. This means that in one month the offspring of a single pair would be more than 46,000. On the other hand, at a temperature of 70° F. the louse reaches maturity in 9 days and produces in the 1 1 days following about 29 young. At this rate in one month a single louse would pro- duce less than 14,000 young. It is thus seen that while with a low temperature the lice can carry on their activities practically unhindered by the parasite, the advent of high temperature is likely to be followed by their destruction by reason of the greater reproductive power of the parasite. The studies of the efi:'ect of moisture are extremeh' limited, but such evidence as has been collected indicates that so long" as the atmosphere is not too dry to prevent the vigor of the food plant and not wet enough to encourage the attack of parasitic fungi, \-ariations in atmospheric moisture have little efl-'ect upon either the louse or its parasite. No studies have been made to show the eft'ect of climate upon the predaceous enemies. The lady-bird l>eetles and their larvcX are the only important forms that attack the lice under low temperatures and they are only rarely suftncienth- al)undant to prevent an outbreak. Some Important Orchard Plant Lici-: 13 In summing up the meager knowledge at hand relative to the effect of climatic conditions on the abundance of plant lice, we may say that a late cool spring is likely to show a serious attack of these insects, while an earl}- warm one is likely to show^ few of them. On the other hand, it is quite possible that a late cool spring might not be accompanied l:)y a plant louse outjjreak be- cause of the destructive effect of a late low temperature, or the activity of lady-bird beetles, or still other agencies less well understood. It is also quite possible that an early warm sprmg might be accompanied by a plant louse pest by reason of an earlier reduc- tion of the parasite. Control Detcnnining JJ'Jicflicr Control Measures Arc Xcccssary In view of the facts just presented showing the uncertainties of aphis outbreak, the first pro])lem of the grower is to determine whether the conditions in his orchard render control measures necessarv. If, as spring approaches, the water sprouts, twigs and smaller branches bear no aphis eggs, treatment for lice is un- necessarv, for there will not be sufficient migration from ad- jacent orchards to create an infestation in the first half of the season. If, on the other hand, as spring approaches, aphis eggs are present on the water sprouts, twigs and smaller branches, treatments should l:>e made as a matter of insurance against damage. The small black eggs are rather inconspicuous and sharp eyes are required to find the first ones. After the grower lias become familiar with their appearance he can pick them out without difficulty. The Problem When the eggs are present the jiroblem of contrcilling the various species of apple aphis appears to involve the destruction of the specimens on the trees before they have a chance to do the damage to fruit and foliage. The aphis appears on the trees in the fail (October and Noveml)er), and eggs laid by them carry over the winter until Inid-opening time. The aphis nnist be attacked just before or during egg-laying in the fall, or while still in the form of the egg resting on the bark of the tree, or in the spring as a nymph that has just hatched. 14 BuLi.t;TiN ;^2H Destroying the Af^his in the Pall In the fall the return of the aphis usually covers a considerable period. In the late fall shining black eggs, immature yellowish eggs and adult aphids are found on the same twig. Anything short of several sprayings would seem to be doomed to failure as a method of control. Destroying the Aphis in the Egg Stage Throughout the winter and earl}' spring the eggs remain on the tree, open to attack, and this would seem to be the logical time to compass their destruction. Alaiiy efforts have Ijeen made to find a substance which Wijuld destroy the aphis egg, not harm the tree, and sell for a price that would not prohibit its use. It can truthfully be said that up to the present time no such sulv stance has been given to the pu1)lic. During the winter and spring of 1917, Dr. Peterson made a preliminary study of the egg and of the effects of certain chemicals upon it. He found that the egg envelope exhibits at least two layers — an outer semi-transiiarent brittle envelope ( glu- tinous wdien the egg is first deposited ) and an inner pigmented elastic meml)rane. A third layer may l)e seen as the nymph hatches, but this is probal)ly the first-cast skin of the nymph. The outer layer appears to exercise a protective function, resisting strains and stresses and retarding evaporation of the body fluids. The fact that this transparent layer encloses the pigmented layer leads one to suspect that, like the jelly on a frog's egg. it may keep the egg warm hv transnntting the sun's rays and retaining the heat into whicli thev are transformed b\- the pigment. Sometime l>efore hatching, the ])eriod ranging from two to thirty days, the outer layer splits along the median line, exposing the pigmented layer, and the egg is thereafter very sensitive to weather (dry air particularly) and insecticides. In the course of his experiments. Dr. Peterson found that the eggs were strongly affected Ijv carljolic acid and l)v winter- strength lime-sulfur. He found that the carbolic acid appeared to soften the outer brittle layer in such a fashion that the egg soon shriveled, while the lime-sulfur appeared to harden it and to prevent hatching. Table T, taken from Dr. Peterson's work, will serve to show the effect of our common sprays upon the eggs and to indicate some sul)stances worthy of further trial. The table is the sum- mary of a large series of experiments. The percentage killed is SoMK Important Orchard Plant Lick 15 determined on the assumption that only that percentage of the total number would hatch which did hatch in the lots laid aside as checks and not treated with an\" suljstance in an)- wa}'. Table I EFFECT OF SPRAYS ON APHIS EGGS PrufDrfioii Kill.'d Materials Used Per cent Lime-sulfur, i-8 or 1-9 85-100 Lime-sulfur, 1-8 plus "Black Leaf 40," 1-500 97 ''Black Leaf 40," 1-500 plus laundry soap, 2 Ih. to 50 gal. . . 45 Laundry Soap, "Fels Naptha," j lb. to 50 gal 5-33 "Scalecide." 1-15 25-65 *'Mechling's Sca!e Oil,'' 1-19 79-90 Sodium Sulfocarbonate. 1-19 85 Sodium Chloride, i gm.* to 5 cc.** water 26-35 Sodium PLvdrnxide, 2 pt. to 98 cc. water 85-95 Crude Carbolic Acid (100%), 2 cc. to 98 cc. of solution, plus soap, 2 \h. to 50 gal. water 93-100 * gm. — gram. ** cc. — culjic centimeters. Several important facts stand out in this table. The deadly quality of lime-sulfur is increased by the addition of 40 per cent nicotine. "Scalecide" is much less effective than lime-sulfur alone. "Scalecide," in which we are assured there is no car- bolic acid, is much less effective than "Mechling's Scale Oil," in which, according- to the makers, is found a percentage of carbolic acid. The great efficiency of a 2 per cent crude car- bolic acid solution to Avhich soap has been added is shown. In the present stage of knowledge none of the su])stai:ces can be recommended for the destruction of the eggs during dor- mancy, but the prospects for the development of such a s]>ra\- seem encouraging. It can be said, however, that the studx- points to the idea that an application of the lime-sulfur ar.d tobacco mixture at the green bud stage, even if not all of the eggs have hatched, is likely to give control l)y reason of the destruction of the unhatched eggs as well as the newly-hatched nymphs. Destroying the Aj^liis in the Sf'i'ing ami Si ininier In the spring, when first hatched, the }()img nvmphs are \-erv delicate, and, consequently, very susceptible to the effect of spraying mixtures. This led investig^ators to place reliance on spring and summer spraying as a means of controlling the i6 Bulletin 328 species. Unfortunately, several years of experience have demon- strated for the rosy louse, at least, that an attempt to control it after the foliage has been curled is sure to fail, and that an attempt to control it after the buds have reall_\- opened is almost certain to fail. The period in the spring when all three species can be brought under control has been thought to be very short, and was thought to extend from the hatching of the egg to the opening of the buds. The problem was further complicated by the fact that the eggs of the rosy aphis hatched, in some cases, coincidently with the opening of the early buds. Table 2 effect of nicotine sprays on rosy aphis Number of leaves Treatment Percentage living at end of experiment 2 Water only 100 2 "Black Leaf 40" (I part) + water (goo parts) 60 'Black Leaf 40" (i part) + water (goo I arts) j -p cuap V- "-< = • "•>j r-" s"-^- 1 2 "Black Leaf 40" -f- soap (2 lbs. { I part) + water to 50 gal.) (700 parts) I 2 'Black Leaf 40"' ( I part) + water (500 parts; 10 'Black Leaf 40"' (i part) + water (500 parts) I + soap (2 His. to 50 gal.) ! In 191 5 Parrott and Hodgkiss^ recommended the delay of the usual winter-strength lime-sulfur, to which 40 per cent nicotine has been added at the rate of ;>4 of a pint to 100 gallons, or about I part of nicotine to 1,000 parts of the spraying mixture, and the application of the mixture at the green bud stage. In 1915 one of our best apple growers almost completely failed to obtain control of aphis by adding nicotine to his pink-bud or cluster-cup sprav at the rate of i to 800, while another claimed perfect control by adding the 40 per cent nicotine to the same spray at the rate of i to 500. To discover the strength of nico- tine necessary for a complete kill of all ages of the rosy ai)his, which has seemed more resistant to spraying solutions than either of the others, the experiment recorded in table 2 was made. * Parrott, P. J., and ilodgkiss, H. E., igi5. Controlling plant lice in aiiple orchards. N. Y. {(icneva) .\gr. Exp. Sta. Bnl. 402. Some Important Orchard Plant Lice 17 Thus it appears that even \\hen used with soap, which seems to give to it the maximum kilhng strength for aphis, i part of the nicotine to 500 parts of water was required to give a com- plete kill. This suggested a numljer of points that needed clearing up, such as : 1. To what extent in comparison with other treatments does winter-strength lime-sulfur effect a control when applied during dormancy and before the eggs have hatched ? 2. To wdiat extent will winter-strength lime-sulfur ap- plied at the green bud stage just after the lice hatch effect a control? 3. To what extent is the combination of winter-strength lime-sulfur and 40 ])er cent nicotine at the rate of 500 to I superior to a combination at the rate of i.ooo to i ? 4. To what extent would a winter-strength lime-sulfur treatment before the lice hatch, followed by an extra treatment of nicotine and soap just after the lice hatch, prove eft'ective? This point was considered because of the fact that in 191 5 the hatching of the rosy aphis was thought to have occurred after the buds opened. 5. To what extent would Scalecide (for which claims have been made ) serve as a control ? In 19 1 6 experiments were planned to answer these questions. They were located on the farm of Mr. John Barclay, of Cran- bury. Mr. Barclay made all the applications according to schedule, and the quality of the spray coatings given by him could not be bettered. The trees were seven years old and very thrifty. The plan of the experiments follows: Bulletin 328 « T4 xx>;xi> •3 5 _-; _-: OJ _r; ^ ^ ^ S'c « tSt c P3 > c >. a s ^^ (U u v W CO iH >^ !:'id 'C s r=; « % H H 3, p. t^ !< K y y X y y y X X X X 6 ;< y y y y y y y X X X X •/. y. y y y y y y y X X X 6 y^ y y y y y y y y. y X X X ^ Vh ^ X 3 y\ y '^ 2 y y y y y y y y y y X X [ d y^ y y y y y y y y y y y y y y y y y y X X X X X X y y y X y y y y. 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