Woolly apple aphid

Woolly apple aphids are covered in distinctive white, waxy filaments that resemble wool or cotton. You will see white cottony masses on apple bark, particularly in crotches, pruning wounds, and graft unions. Affected areas develop galls and cankers. Honeydew attracts ants that farm the aphids. Most damaging on young trees and in warmer regions; western Washington sees minimal damage.

For young orchard trees, prune out heavily infested wood in late winter. Spray horticultural oil in late fall or early spring before buds break to smother overwintering aphids. For landscape apples, accept minor gall formation. Do not over-fertilize. Encourage natural enemies by avoiding broad-spectrum pesticides.