Woolly beech aphid overwinters as eggs that are laid around buds and in bark crevices in autumn. The eggs hatch in spring a few weeks after new foliage has appeared.
The pale yellow aphids suck sap from the underside of leaves and can form dense colonies that are hidden under a white waxy fluff that is secreted by the aphids. They also excrete a sugary honeydew that makes the foliage sticky and encourages the growth of sooty moulds. Heavily infested leaves may be distorted but otherwise the tree’s growth is unaffected.
For most of spring and summer, the aphids are wingless forms that reproduce by producing live young. In mid-summer, winged forms develop that fly off in search of new host plants. These winged woolly beech aphids can be mistaken for glasshouse whitefly or woolly aphid, neither of which occur on beech.