rttwtf of ihe Uniied Stales Governmiii. 
 
 i No 20, Revised Edition 
 
 United States Departmenl of Agrj 
 
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 t / 
 
 libranr* 
 
 BUREAU OK ENTOMOLOGY, 
 i '■ HOWARD. Km. >ni.>i. mint and ChM 'it 
 
 mi: wooi.n \niis OF Tin: 
 
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 .[. vrri: \i; \\. i: wi> uktiioh ok work. 
 
 Throughout tli<- -uiniiirr on the lower portion <»f the trunk and par- 
 ticularly <>n the water sprouts of the apple may often be Been small 
 bluish-white Hocculent i>r cottony patches, which indicate the presence 
 of oolonies of our of the worst enemies of tin' apple, viz, the insecl vari- 
 ously known in 
 this country as the 
 " apple-root plant- 
 . " "woolly 
 apple louse," 
 
 " woolly ,i ph i-." 
 
 etc., ami abroad 
 very generally as 
 the "American 
 blight." It i 
 
 in two forms, the 
 
 one ju.-t referred 
 
 to, above ground 
 
 on the trunk or 
 
 Wat) r shoots, and & o 
 
 anotherinhabiting , .. , u ,, . , pb M ■ ,, lnr _ 
 
 tin 1 r> m >t 9 am In.'' < 
 
 'i.ni rpm.n ' nal.) 
 
 open to observa- 
 tion. Clow !y paralleling in these particulars the grape phylloxera, the 
 
 damage from the woolly aphis i- also almost altogether 'lu>' to the root 
 form, tin' atrial colonies causing Bcarcely any injury. On the roots 
 attacks induce enlargements <>r ^nlls or Bwellings very similar to those 
 produced by the phylloxera, ami in the cracks of these galls and BWell- 
 the root form occurs in clustered masses. The injury to the trees 
 is tlue both to the Bucking up ami exhaustion of the vital plant juices 
 ami to the poisoning of the parts attacked, as indicated by the ( 
 quent abnormal growths. 
 
 The damage i- particularly serious in the case of ni tock ami 
 
 young ire-- and i- less often important after the tree lias once become 
 well established and of Bom< - Where this insect i~ abundant all 
 
the roots of a young tree to the depth of a foot or so hecome clubbed 
 and knotted by the growth of hard fibrous enlargements, with the result, 
 in a year or two, of the dying of the rootlets and their ultimate decom- 
 position with attendant disappearance of the galls and also of the aphides, 
 so that after this stage is reached, the cause of the injury is often 
 obscure. On the trunks the presence of the aphides sometimes results in 
 the roughening 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 the insects collect particularly in the axils 
 of the leaves, often eventually causing them to fall, and on the tender 
 greener side of the stems. The damage above ground, though com- 
 monly insignificant, is useful as an indication of the probable existence 
 of the aphides on the roots. A badly attacked tree assumes a sickly ap- 
 pearance 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. Injuries from the woolly aphis are almost altogether confined 
 to the apple, even the wild crab not being so liable to attack or at least 
 injur}' by it. There is, however, some difference exhibited by different 
 varieties of apple in immunity, and particularly is the Northern Spy 
 proof against it, and it is possible that, as in the case of the grape 
 phylloxera, by employing root stock from seedlings of the more resist- 
 ant varieties or from wild crabs, considerable protection would result. 
 The character of the soil also exerts some influence — that is, loose dry 
 soils are favorable and wet compact ones are unfavorable to the aphis. 
 
 ORHilX AND DISTRIBUTION. 
 
 There is considerable difference of opinion as to the origin of the 
 woolly aphis of the apple. The belief has fluctuated between a Euro- 
 pean and an American origin for this insect, but the weight of evidence 
 seems to indicate the latter. At any rate, it is an insect which is most 
 readily carried from place to place with nurserj- stock of the apple, and 
 it has been so transported to practically all the important countries of 
 the world which have been reached by colonization or European settle- 
 ment. The woolly aphis was first noticed in England in 17S7, on some 
 stock imported that year from America, and was early called the Ameri- 
 can blight. Hausmann described it in 1801 as infesting apple trees in 
 Germany, and within the next twenty-five years it was recognized as a 
 serious enemy of this fruit tree throughout England, Belgium, northern 
 Erance, and Germany, but seems never to have been especialhy notable 
 in the warmer latitudes of Europe. 
 
 It was very early introduced into Australia and New Zealand, and is 
 known in India and Chile, and probably is as widespread as any of the 
 common injurious fruit pests. Notwithstanding the possibility of its 
 being a native American insect, it did not attract attention in this 
 
country much before I860. It- Bpread wnce has, however, been rapid, 
 and ii now occur- practical lj wherever the apple is grown, It has 
 been reported to this Bureau from no less than thirty-fiv< 3l ttee and 
 Territoriee and nearbj one hundred localities. It i- particularly abun- 
 danl and injurious in the latitude of the Ohio Valley. While seem 
 ingly, therefore, somewhal affected bj Bevere cold, it is able to thrive 
 in the climate of the northern tier ol States on the one band and in 
 thai of Louisiana, New Mexico, and 
 southern Californii the other. 
 
 n k ii R \l. lll-ToKY and BABTTS. 
 
 In common with most aphides, 
 this species lias a complicated life 
 history . some of the details of which 
 arestill lacking. Thecommon tonus, 
 both on the roots and above ground, 
 wingless aphides, not exceeding 
 one-tenth of an inch in length, and 
 of a reddish-brown color, and abun- 
 dantly covered, especially in the 
 aerial form, with a Bocculenl waxy 
 
 retion. These arc so-called 
 
 agamic females and reproduce them- 
 selves by giving birth, as obsei 
 by many entomologists, to living 
 young indefinitely, perhaps tor years, 
 without the intervention of other 
 forms. The newly horn larva- have 
 none of the white excretion, which, 
 however, soon appear- as a minute 
 down when they begin to feed. 
 
 These aphides are also peculiar in 
 lacking the honey tubes common to 
 most aphides, bul exude the honey- 
 dew from the tip of the body. In ' October or November, or earlier in 
 South, among the wingless ones numbers of winged individuals 
 appear, which are also all females, and are the parents, as shown by 
 the observations, partly unpublished, of M< bstb. Howard and Pergande, 
 oi a true Bexed generation of minute, wingless, larviform aphides, the 
 females of which, as in the case of the -rape root-aphis, give birth to a 
 single "winter egg." This egg is attached within a crevice of the 
 hark, and, probably, following the analogy of the phylloxera, hatches 
 in the spring into a female aphis which originates a new aerial colony. 
 The winged females appear somewhat abundantly in autumn, and are 
 one of the means of the dispersal ol the inseel They arc very minute. 
 
 I w 
 
 a, Rool ■>: \ iui (rating deforma- 
 
 tion 
 
 . 
 
 i 
 
clear-winged, gnat-like objects, greenish-brown, almost black in color, 
 with the body covered with more or less of the cottony excretion. 
 
 The aerial colonies are probabh- killed out every winter in the colder 
 northern districts, but in the warmer latitudes the partly grown indi- 
 viduals, at least, survive protected in crevices or under bits of bark, 
 and remain more or less active during winter and renew the colonies 
 the following spring. This has been shown to be true in the District 
 of Columbia, and also in the interior regions of the same latitude, in 
 spite of the much colder winters. The root form survives the winter 
 usually in an immature condition, viz, larvae in various stages of 
 development, and both in latitudes where the aerial forms are killed 
 by the severity of the winter and elsewhere it seems probable that there 
 is a regular upward migration in spring and early summer from the 
 roots, the aerial colonies appearing first near the crown and at a later 
 period on the higher parts of the trees. At any time during the sum- 
 mer and fall there ma}' be migrations to the roots, and throughout the 
 year the subterranean colonies are maintained. 
 
 The spread of the insect is accomplished in part by the viviparous 
 females, which appear in late summer, but quite as commonly perhaps 
 by the transporting of young or parti} 7 grown individuals from tree to 
 tree or to distant orchards by means of birds or insects to which they 
 have attached themselves. Its wide distribution is usually dependent 
 on the traffic in nursery stock. 
 
 REMEDIES AND PREVENTIVES. 
 
 The foregoing account of the habits and characteristics of the woolly 
 aphis will enable us to suggest certain measures to control it. The 
 aerial form presents no especial difficulty, and can be very readily exter- 
 minated by the use of any of the washes recommended for aphides, 
 such as kerosene emulsion, a strong soap wash, resin wash, etc., the 
 only care necessary being to see that the wash is put on with sufficient 
 force and thoroughness to penetrate the covering and protecting cot- 
 tony excretion. If the wash be applied warm, its penetration will be 
 considerably increased. 
 
 The much more important root form, however, is more difficult to 
 reach and exterminate. Any of the remedies which are applicable to 
 the phylloxera will apply to the apple root-aphis, such as the use of 
 bisulphid of carbon or submersion. The common recommendations 
 are of applications of strong soap or tobacco washes or kerosene emul- 
 sion to the soil about the crown, or soot, ashes, or tobacco dust buried 
 about the roots, also similarly employed are lime and gas lime. 
 
 The most generally recommended measure hitherto is the use of hot 
 water, and this, while being both simple and inexpensive, is thoroughly 
 effective, as has been demonstrated by practical experience. Water at 
 nearly the boiling point may be applied about the base of young trees 
 
 
without the slightest danger of injury to the trees, and should be 
 in sufficient quantity to thoroughly wet the Boil to .1 depth ol Beveral 
 inches, as tin- ;i 1 > 1 1 i < 1 1 ■ - maj penetrate nearly a foot below the Burl 
 To facilitate the wetting of the roots and the extermination <»f the 
 aphides, as much of the Burface Boil as possible Bhould be first removed. 
 
 Kerosene emulsion, at '_'n to 30 per cent of kerosene, has given good 
 results in Georgia, as reported bj R. I. Smith. 1 
 
 Mr. .1. M. Stedman was the first to demonstrate the protective as well 
 as remedial value of finely ground tobacco dust. The desirability ol 
 excluding the aphis altogether from nurserj stock i.- at once apparent, 
 ami this Mr. Stedman has Bhown to be possible by placing tobacco 
 du.-t freely in the trenches in which the seedlings or grafts are planted 
 and in the orchard excavations for young trees. Nursery Btock may be 
 continuously protected by laying each Bpring a line of the dust in a 
 small furrow on either side of the row and as close as possible to the 
 tree, covering loosely with earth. For large tree-, both for protection 
 and the destruction of existing aphides, from 2 to 5 pounds of the duel 
 should be distributed from the crown outward to a distance of 2 feet, 
 tirst removing the surface Boil to a depth of from 1 to 6 inches. 
 
 Since it- early recommendation marked Buccese has been reported 
 from the use of tobacco dust. A notable instance is thai given by Mr. 
 M. B. Waite, of the Bureau of Plant Industry, who applied a ton of 
 tobacco waste, costing $25, in bis orchard, with the result of entirely 
 renewing the vigor of his trees and producing a strong stubby growth of 
 twigs. A peck of tobacco dust was placed about each of his larger 
 trees in a circle of '_' or 3 feel around the trunk, and a Blightly smaller 
 amount aboul trees from one to three years old. 
 
 The tobacco kills the aphides By leaching through the soil, and act- 
 as a bar for a year or bo to reinfestation. The dual i- a waste producl 
 of tobacco factories and costs about 1 cent per pound, and p — 
 the additional value of being worth fully it> cost as a fertilizer. 
 
 The use of bisulphid of carbon for the woolly aphis i> the aam< 
 for the grape root-aphis. It Bhould he applied in two or three holes 
 about the tree to a depth of ii to 12 inches and not closer than H feel 
 to the crown. An ounce of the chemical should he introduced into each 
 hole, which Bhould he immediately closed. The hisulphid evaporate- 
 and penetrate- throughout the -oil and readily and promptly kills the 
 aphides. It does not. however, furnish any protection from future 
 attacks, and is attended witli danger to the tree unless the precautions 
 named are carefully observed. That it is highly inflammable should also 
 instantly borne in mind. If it i^ to he used at all extensively, an 
 automatic injecting device should he secured. The chemical 
 about li> cents per pound in 50-pound cat - 
 
 'Bui. 60, Bur. Ent., U. S. Dept. 1906. 
 
6 
 
 Badly infested nursery stock should be destroyed, since it would be 
 worth little even with the aphides re moved. Slightly infested stock can 
 be easily freed of the aphides at the time of its removal from the nursery 
 rows. The soil should be dislodged and the roots pruned, and in 
 batches of a dozen or so the roots and lower portion of the trunk should 
 be immersed for a few seconds in water kept at a temperature of 130° 
 to 150 F. A strong soap solution similarly heated or a fifteen times 
 diluted kerosene emulsion will give somewhat greater penetration and 
 be more effective, although the water alone at the temperature named 
 should destroy the insects. This treatment is so simple and inexpensive 
 that it should always he insisted upon by the purchaser if there be any 
 indication of the presence of this insect, and stock exhibiting much 
 damage should be refused altogether. 
 
 After planting, if the trees be kept in vigorous growing condition by 
 careful cultivation and, if necessary, proper fertilizing, damage from the 
 aphides is much less apt to occur, and the principal danger period, 
 namely, the first two or three years after planting in the orchard, will 
 pass in safetj'. The value, as a means of protection, of thorough culti- 
 vation and good care of young orchards can not be too strongly 
 insisted upon. Vigorous growing trees have a* decided power of resist- 
 ance and are able to sustain with comparatively little damage the 
 presence of the root-aphides, while illy-cultivated and neglected orchards 
 are especially liable to injury. 
 
 The woolly aphis is subject to the attacks of a number of natural 
 enemies, including the parasitic chalcis Hy, Aphelinus matt Haldemann, 
 and the larva of a syrphus Hy, Pipiza radicum Walsh and Riley, and 
 also the larva and adult of several species of ladybirds, the larvae of 
 lace-wing flies, and spiders, etc. In the East a very small brown species 
 of ladybird, Scymnus eervicalis Muls., is often present in some numbers, 
 and the common nine-spotted ladybird, Cocdnella 9-notata Hbst., is also 
 an active enemy of the woolly aphis. The nine-spotted ladybird has been 
 used very successfully in California, on the authority of Mr. Ellwood 
 Cooper, to rid trees of root-aphides, this being effected by colonizing the 
 larvae of the ladybird at the base of the infested tree. All the para- 
 sites mentioned do much to keep the root-aphides in check, and in the 
 case of old well-established trees are in most instances a sufficient pro- 
 tection, hut in the case of young trees and nursery stock, where the 
 damage from the aphis is much more rapid and serious, the use of the 
 direct remedies outlined should not be neglected, and particularly should 
 the nursery treatment be insisted upon. 
 
 Approved : 
 James Wilson, 
 
 Secretary of Agriculture. 
 
 Washington, D. C, June 23, 1008. 
 
 O 
 
■in in in 
 
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