SB 

 818 

 C578 

 ENT 



- i. mt. afug 



No. 20, Revised Edition. 



lited States Department of Agriculture, 



BUREAU OF ENTOMOLOGY, 



L. O. HOWARD. Entomologist and Chief of Bureau. 



THE WOOLLY APHIS OF THE APPLE. 



{Schizoneura lanigeni IJansniann.) 



By C. L. Marlatt, 

 EntomoJofjist and Asfiistant Chief of Bureau. 



GENERAL APPEARANCE AND .METHOD OF WORK. 



Throughout the summer on the lower portion of the trunk and par- 

 ticuhirly on the water sprouts of the apple may often be seen small 

 bluish-white flocculent or cottony patches, wliich indicate the presence 

 of colonies of one of the worst enemies of the apple, viz, the insect vari- 

 ously known in 

 this country as the 

 " apple-root plant- 

 louse," "woolly 

 apple louse,'' 

 " woolly aphis," 

 etc., and abroad 

 verj^ generally as 

 the "American 

 blight." It exists 

 in two forms, the 

 one .just referred 

 to, above ground 

 on the trunk or 

 water shoots, and 

 anotherinhabiting 

 the roots and not 

 open to ol)Scrva- 



tion. Closely paralhiling in these particulars the grape phylloxera, the 

 damage from the woolly aphis is also almost altogether due to the root 

 form, the aerial colonies causing scarcely any injury. On the roots its 

 attacks induce enlargements or galls or swellings very similar to those 

 produced bj' the phylloxera, and in the cracks of these galls and swell- 

 ings the root form occurs in clustered masses. The injury 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 b3'- the conse- 

 quent abnormal growths. 



The damage is particularly serious in the case of nursery stock and 

 3'oung trees and is less often important after the tree has once become 

 well established and of some size. Where this insect is abundant all 



Fig.]. — Woolly aphi^ (Schizoneuivi laniaem): a, A'ja.mk: fomale ; l>. hir- 

 valaphis; c.pupa; rf, winged female with anreiiiiaenlar!ieilal)()ve. All 

 greatly enlarged and with waxy excretion removed. (Original.) 



