APPENDIX 



333 



THE WOOLLY APHIS OF THE APPLE. 



{Sc/iizotieura lanigern Hau.siiiami. i 



By PoKK. C. li. Maklatt. 



aENEKAL APPEARANCE AND METHOD OP WORK. 



Throuifhout the summer on the lower portion of the trunk and particu- 

 larly on the water sprouts of the apple nuiy often be seen small bluish-white 

 flocculent or cottony patches, which indicate the presence of colonies of 

 one of the worst enemies of the apple, viz.: the insect variously known in 

 this country as the 

 ■'apple-root plant- 

 louse," "wooly ap- 

 ple louse, ' ' ' 'woolly 

 aphis," etc., and 

 abroad very gen- 

 erally as the "Am- 

 erican blight.'' It 

 exists in two 

 forms, the one just 

 referred to, above 

 ground on the 

 trunk or w a t e r 

 shoots, and an- 

 other inhabiting 

 the roots and not 

 open to observa- 

 tion. Closely par- 

 alleling 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 by the phylloxera, and in the 

 cracks of these galls or swellings 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 by 

 the consequent abnormal growths. 



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

 trees and less often important 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 growth 



Fig. 1 — Woolly aphis ( Schizoneura lanh/cra ) — a, Agamic female; 

 b, larvel louse; c, pupa; d, winged female witli antenna en- 

 larged above; all greatly enlarged and with waxy excretion 

 removed (original). 



