Woolly aphids are small, sap-sucking insects that cover themselves in a white, waxy, woolly-looking secretion. This disguises them and gives them some protection from predators and from being affected by some chemical, contact, insecticides. The actual aphids themselves, underneath the woolly covering, are black or brown in colour.
Unlike most other aphids, woolly aphids mainly suck sap from the woody stems, rather than the leaves, but may also attack buds and leaves.
The woolly covering means they are often confused with mealybugs or even fungal plant diseases.
Woolly aphids become active in spring, usually feeding on thinner or weaker stems, branches or thinner areas of bark. Areas around pruning cuts are often favourite feeding and breeding haunts.
Numbers reach a peak by late summer, when winged forms fly away to look for new host plants.
Woolly aphids overwinter as a small, immature stage, which hide in crevices on the stems and branches or in cracks in the bark.