Seasonal development and life cycle—Woolly
apple aphids
Woolly apple aphids overwinter as adults on roots and aerial parts of apple trees. By early summer,
large numbers of nymphs are produced. First-instar nymphs migrate up and down the tree; those from root
colonies may move up the tree and those from aerial colonies may move to the roots, entering through
cracks in the soil. First-instar nymphs are primarily active from mid-June to mid-September. Once they
find a suitable spot to settle, they begin to form new colonies. Adults have reddish to purple bodies
and are completely covered with woolly white wax. Overwintering aerial colonies do not produce the woolly
white wax and are therefore more difficult to detect than are summer colonies.
Infestations are spread from tree to tree by wind and birds. Woolly apple aphids may also be brought
into the orchard on nursery stock. | 
Aerial
colony of woolly apple aphids
Root
colonies cause swollen, root galls
|
