' f \S Circular No. 81 "" — ^_^' United States Department of Agriculture, BUREAU OK ENTOMOLOGY. L. O. HOWARD. Entomoiogiit »nd Chief of BuTcmu/t ,// "" l0 >*- THE kPHIDEH IFFECTING NIF^^Kt/ INTRODUCTION. V *■ " ,• tf*' V \?fa'' 'eVi' 1 Four species of aphides, or "plant-lice," coininoin£^fnz0MR!|t$ an^h in the United States, namely, the woolly apple aphis (Scfi ts enmtf t fiani- I [ausm. . the European grain aphis (Siphoeoryru •<>•■ na Fab. ). the apple : ij > 1 1 i - (Aphis mali Fab.), and the rosy apple aphis (Aphis mali- • Fitch). The first mentioned the woolly apple aphis- infests the roots of the apple, producing a knotted, distorted growth, and also the limbs and branches, where the colonies are quite conspicuous from the white, flocculent material which the insects Becrete. This species ha- been treated in Circular No. 20, second series, of tin- office, to which the reader i- referred. The other specie- above men- tioned infest the more tender growing shoots and leave- of the apple, and are especially injurious when occurring on young orchard or nur- sery tree-, which are more commonly infested than older trees, making comparatively little annual growth. Water -proiit- also are frequently infested, and the -hoot- of top-worked trees are especially subject to attack. The presence of these insects i- indicated by the curled and distorted condition of the more terminal leave-, and if a plant showing these symptoms be closely examined, -mall oval or pear-shaped soft-bodied aphides, greenish or pink in color according to species, will be found on the under surface of the leave-, along the tender- stem or elsewhere, often practically covering these part- (see figure 1). Each aphis is provided with a -mall beak, which is pushed down into the tissues of the leaf or stem and by means of which the sap i- sacked Up for food. When the in-ects are abundant, the drain upon the plant i- very great, interfering with it- proper growth and development, ami in extreme cases causing the death of the infested part-. The leaves and -hoot- of plants infested by these in-ects are fre- quently seen to be covered with a black substance, i- if dusted with N - 1 —07 soot. This is due to a black fungus which grows on the "honey dew" excreted b}' the aphides. This may be produced in such quan- tities as to coat the leaves, and is attractive to various species of ants and wasps frequently to be seen attending the aphides or frequenting plants infested by them. The black fungus noted is not in itself especially injurious, bat it usually indicates the presence of aphides, which mav be v^e>~>- the cause of ma- ^%^ terial injury. APHIDES IN GENERAL. The insects of the family Aphi- didse, or " plant- lice," are espe- cially remarkable on account of their mode of de- velopment. This will vary con- siderably accord- ing to the species, but at some time in the life of a species true sexes are produced, usually in the fall, the sexual female depositing eggs after the usual manner of insects. Eggs deposited in the autumn pass the winter in this condition, and Fig. 1. — Terminal shoot of apple infested with the apple' aphis [Aphis mali), f Lpj r hatch ill"' ill showing condition of leaves. (Original.) _ _ *» the spring is more or less coincident with the revival of growth of vegetation. From the winter eggs is produced a generation of females, usually wingless, which reproduce agamic-ally— that is. without the intervention of males, many species, as those under consideration, giving birth to living young. The adult aphides of this first generation are termed "stem-mothers." The offspring of the stem-mothers (second gener- ics, si] ation) may be winged or wingless, or both forma may occur; they reproduce agamically, some species being oviparous and depositing peeudoova, or eggs which do not require fertilization for develop- ment; while others are viviparous and bring forth young alive, the peeudoova developing within the body of the parent. There may be u succession of generations produced agamically, with most species this mode of reproduction continuing until the approach of autumn, when the true sexes appear and deposit eggs; <>i - a species ma\ be more or less biennial, some indh iduals producing true sexes only every second year. With -till other species, the true sexes of which are at present unknown, agamic reproduction possibly continues for a series of year* The same species of aphide may present several forms, as wingless agamic females, winged agamic females, and the true sexual forms; in the last the male may be winged and the female wing- less, or both sexes may he wingless. The different generations of a given Bpecies may vary more or less, and in Borne instances this is the cas to such an extent that they appeal- to belong to distinct Bpecies. Aphides are enabled to increase with great rapidity by reason of the short time required by their young to reach maturity. Their powers of multiplication are so great that if unchecked the product of a single insect during one season would run up into the billions. Very fortunately, however, there arc many drawbacks to their increase, among which are certain weather condition-, parasitic and predaceous ts, and fungous diseases. When one or more of these agencies are in abeyance, aphide- may become very numerous and destructive locally or over a considerable ranee of territory. THE EUHOPEAH DRAIN \rill-. I ih.) The European grain aphis ( fig. 2) i- the common greenish apple aphis of the United State-, and i- the species erroneously considered by Fitch a- identical with the European Aphis iinili Fab., by which name until recently it ha- been very generally known in our literature. Two species, however, have been confused under thi- name, the present and the following 1 , which fact was recognized by Mr. Th. lViLrande-, and also by Or. .1. B. Smith. Prof. E. IV Sanderson in \'. { ^i described this inflect a- new under the name of Aphis v'-- ',:. I >ut Pergande ha- sub- sequently shown that the insect i- identical with the European grain aphisi Aj'/n's.- Fab.), and consider- that the species really belong- to the genus Siphocoryru of Passerini. Thi- species i- recorded from various widely separated localities, and i- probably very generally distributed throughout the United State-. Twenty-two plant- upon which it has been observed are recorded, comprising eight trees, four Is or herb-, and ten grains and grasses. < H orchard fruit-, apple, quince, and plum are food-plant-: and of grains, rye. oat-, and ten wheat are infested, the last, according to Prof. F. M. Webster, often being quite seriously injured by the aphides in the fall, the yourg plants being attacked at or just below the ground. Fig. 2.— The European grain aphis (Siphocorynt aveme), a common aphis on apple: a, migratory , sexual female; c, antenna of migratory female; (/, side view of end of body of winged male; < . under side of end of body of male: /, under side of end of body of sexual female. All greatly enlarged (from Pergand- NATURAL HISTORY AND HAHITS. This species has been well treated by Sanderson and Pergande. and has been found to present a very interesting life history. The shiny, jet-black winter eggs are deposited by the females in the fall around the buds of the more terminal shoots, at crotches of limbs, and in cracks [Cir. 81] and under scales of the bark. The eggs, are quite -mall. l>nt may be readilj detected with the unaided eye. These batch in spring, about the time the young leaves of the apple are pushing out, and the small, enish '■lire.'* often occurring in large numbers, at once attack these parts. These insects, when fully grown, are the Btem-mothers, and soon begin the production of living young, most oi which develop into the winged agamic form which migrates to other trees and toother localities, where new colonies are Btarted, the progeny of the third generation also being winged and wingless. In all, Borne five genera- tions of aphides develop on the apple, but by early July in the lati- tude of Washington the tree- are free from them, and the aphides have become established on grains and grasses <>r other host plants. Upon the approach of fall, apple trees are again infested by the return mi grants from the grasses and grains, the true females are soon produced, and the winged male- come from the grasses upon which they have developed. Winter e are deposited during September, October, and early v \ ember in the manner indicated. THE APPLE APHIS. In general appearance the apple aphis (fig. 1 1, or apple leaf-aphis, is much like the preceding, with which it has been confused. The body is pear-shaped, instead of oval as in S. aven '. the colors of both being yellowish green, greenish, or darker, varying considerably in detailed markings and in the several generations. ■ Aphis malt Fab. {pomi De Geer) is of European origin, and has only recently made it- appearance in this country, Mr. Pergande having first -ecu specimens collected in the United State- in L897. However, at I the the present time it is widely distributed, having been ipMi recorded from New Jersey, Delaware. New York. Con- tw * necticut, Colorado. Michigan, Alabama, and Georgia. The records of thi- Bureau -how it to occur in Kentucky. Louisiana, Oregon, Pennsylvania, Nebraska, and Arkansas. In this country the in-ect appear- to infest apple (fig. l) principally, if not entirely. though in Europe it infests in addition the wild crab( J f^n« pear, and white thorn {CratsegxiA oxyacanth* >. NATl'KW. HISTOKY AM' li The apple aphis has been studied by Dr. J. B. Smith and Trot E. Di Sanderson. Winter eggs (fig. 3) are deposited by the sexual females [Ox - in the fall, oviposition beginning somewhat earlier than but overlap- ping with that of the preceding species; they are placed in similar situations, and are not distinguishable from tho.-e of Siphocoryne Fig. i — Apple aphis (Aphis mali);. a, winged agamic form; 6, pupa; e, wingless agamic form; d, recently born aphis. All greatly enlarged (original). avenx. The}' hatch perhaps somewhat later in the spring, and after the foliage is further advanced and, like the species next considered, the aphides developing from them cause a greater curling of the leaves. The apple leaf TnamTTTr^ cs^gfea aphis infests the apple throughout the year and for this reason is capable of more injury than the other species herein treated. Upon the hatching of the winter eggs in spring a succession of agamic gen- erations is produced, the earlier ones, except the first, with numerous winged Fig. 5.— Apple aphis [Apkis mali): The true sexual forms: individuals which migrate a. male; b, female. Greatly enlarged (original). . , . , to other trees and estab- lish new colonies. In New Jersey, as found by Doctor Smith, there may be during the season seven agamic generations followed by the development of the sexual wingless male- and females (fig. 5) in the fall. [Cir. SI] Till ROM U'l'l.i: Mill-. Tin' rosy apple aphis (fig. ft), regarded by Pergande aa Aphis rnali- folia Fitch, and determined bj Sanderson a- Aphi*norbi Kaltenbach, i- readily distinguished from the preceding by its larger size, rounder body, and usual 1) rosj color, which, however, may \ar\ from sal n to tan or even to slat) gray or black, the bod) I >< ■ i i > -_ r covered with a whitish pulverulence. This species is verj general!) distributed in the United States, occurring in Buch widely separated States ;i- Illi- nois, Connecticut, New Jersey, Virginia, Washington, California, Sotiih Carolina, and West Virginia; it occurs also in Canada, rhe species is common on apple, hut has been taken by Sanderson on pear. born aphis. All L-rently enlarge I In Europe tin' food plant- <>f Aphis eorbi, in addition t.» apple, are yaccintha, S>>r ! >"s,/,i<'i/j>,i/->'i, S. domestica, ami S. /"/•/>"/" in e Hiarrom . The life history of this species i- but imperfectly known. Winter eggs an> deposited in tin- autumn by sexual females, and more often on tlio trunk and larger limbs than with the other spe< ies mentioned. They hatch in spring as the apple leave- are pushing out, and theyoung aphides infest the young leave* and later the tender -hoot- ami foliag the latter thus becoming usually badly curled. Three generations from the egg are said to occur on the apple in the spring, many individuals of the second and third generations developing wings ami migrating toother trees and toother host plant-. After the third generation the apple i- deserted by the insects until fall, when the return migrants appear ami give rise to the true sexual form-, the females deposil eggs a- described. • Ml NATURAL ENEMIES OF APHIDES. Aphides are attacked by various species of predaceous and parasitic enemies, and by fungous diseases, and under certain climatic conditions Fig. 7.-Two-spotted ladybird {Adalia bipunctala): a, larva, b, mouth parts of same; c claw of v ftme - rf. pupa; - . adult or beetle; /. antenna ol same, a common arboreal ladybird. All enlarged 'from Marlatt). these agencies exert a very important influence in their control. Species of ladybirds or Coccinellidaa (fig. 7). aphis lions— the larvse of Chryso- Pig. 8.— The golden-eyed lace-wing lly (Cftrysoj :utata): a, eggs; b, full-grown larva; e, foot of same; l>- OF O IMTROL. /' \ming. As l»:i~- been stated, the aphides under consideration pass the winter in the egg stage od the apple, the eggs being deposited more <>r less promiscuously over the more nearly terminal twi With young trees especially, which are seen to be heavily stocked with tin' eggs, the latter may be largely removed during the work of pruning, and the pruninga should be collected and burned. The insects in the egg condition are frequently distributed on nursery stock; therefore, it' in planting trees this stock be well pruned and the pruninga destroyed, the establishment of the aphides in young orchards may be often prevented or delayed. Winter spraying for destruction of eggs. — Several -pray-; have been at various times more or less used for the destruction of the e<_ r !_ r - on the trees; among these are strong lye water, whale-oil soap, and kero- -ene and crude petroleum in soap or mechanical emulsions with water or evt 11 undiluted. On the whole, very little of practical good seems to have followed these treatments, the eggs being largely resistant to Buch insecticides as are not bo strong as to injure the trees. In the experience of Prof. .1. M. Aidrich, however, excellent results have followed the 086 of lime-sulphur wash, most allot' theeggsof the apple aphis having been destroyed by one thorough application in spring shortly before the buds opened. The use of this wash for the eggs of aphides would also control the San Jose scale when present. Spring and summer truitmriit*. Ktl'ective work in controlling these insects may be done in the spring just after they have hatched from eggs and have collected on the expanding foliage. Tree- Been to tie badly infested at this time should be thoroughly -prayed, taking pain- to wet as completely a- possible all part- of the leaves, twigs, and branches. However thoroughly the work may be done, some of the "'lice " are almost sure to escape destruction, owing to the difficulty of forcing the spray between the unfolding leaves, more or less covered with hair-, where some of the in-ect- will have penetrated. A -u quent treatment in the cour-e of a week should usually lie made, espe- cially if the first application i- -.en to have been unsatisfactory. After the foliage is well out and more or less distorted from the presence of the aphide-. effective Bpraying is quite difficult, - [Cir.Mj 10 many of the insects on the lower surface of the curled leaves will not be hit by the spray. Repeated applications must be made, therefore, as necessary to keep the insects under control. It will often be found practicable to bend over and immerse the terminal shoots of badly Infested young- trees in a bucket of the spray solution, and *'us treatment will be very effective. Spray misatures. — The lime-sulphur wash for the destruction of win- ter eggs is made according to the usual formula for the wash, namely, lime 20 pounds, sulphur 15 pounds, water to make 50 gallons, and boiled for one hour. After the trees are in foliage, a more dilute contact insecticide must be employed, as strong tobacco decoction, 15 or 20 per cent kerosene emulsion, 15 per cent crude petroleum emulsion, or whale-oil soap at the rate of 1 pound for each -1 gallons of water. Since aphides secure their food b} r sucking up sap from within the plant, none of the arsenical poisons would be effective. Tobacco decoction may be made from tobacco stems and other refuse tobacco by boiling at the rate of 1 pound for each 1 or 2 gal- lons of water, sufficient water being added to make up for that lost in boiling. A 20 per cent kerosene or crude petroleum emulsion is made as follows: Whale-oil or other soap pounds.. 2 A Kerosene or crude petroleum gallons. . 10 Water to make gallons. . 50 The soap is dissolved in 5 gallons of hot water, which is at once poured into the spray-pump barrel. The 10 gallons of kerosene or crude petroleum is next added and the whole thoroughly emulsified by pumping it back through the hose into the barrel for 6 or 8 min- utes. After the oil has become thoroughly emulsified, the barrel ifi filled with water, and the preparation is ready for use. When a less amount of emulsion is desired than the quantity above indicated, it may be reduced as desired by observing the proportions given. Approved : James "Wilson, Secretary of Agriculture. Washington, D. C, December 18, 1906. [Cir.81] o WASHINGTON „ )VC sv t s UNIVERSITY OF FLORIDA 3 1262 09216 4499