SB 
818 
C57 
ENT 
No. 20, SECOND SERIES. 
8 
uted States Department of Agriculture, 
DIVISION OF ENTOMOLOGY. 
THE WOOLLY APHIS OF THE APPLE. 
(Schizoneura lanigera Hausmann. ) 
GENERAL APPEARANCE AND METHOD OF WORK. 
Throughout the summer on the lower portion of the trunk and par- 
ticularly on the water sprouts of the apple may 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,’’ 
‘woolly apple 
louse,’ “‘ woolly 
aphis,’”’ etc., and 
abroad very gen- 
erally as the 
SAC ime Ta. Cuan 
blight.” It exists 
in two forms, the 
one just referred 
to, above ground 
on the trunk or 
water shoots, and 
another inhabit- 
ing the roots and Fig. 1.—Woolly aphis (Schizoneura lanigera) : a, agamiec female; BD, lar- 
val louse; ¢c, pupa: d, winged female with antenna enlarged above; 
not open to obser- all greatly enlarged and with waxy excretion removed (original). 
vation. Closely 
paralleling 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 and 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 is less often important after the tree has once become 
