Woolly aphid A white, cotton wool-like covering on stems is the trademark of the woolly aphid. These pinkish-brown aphids secrete a waxy substance under which they feed undisturbed on the tree sap, usually choosing to drink from apple trees, crab apples, cotoneasters and pyracanthas. They reach noticeably high numbers in late spring, with the majority of the colonies clustering around old pruning wounds and splits in the bark before they move to the younger branches later in the season. Their feeding results in a soft, knobbly swelling which, although perhaps not a real problem in itself, can split during frosty weather, providing an entry point for other diseases such as apple canker. The aphids are not great travellers, often appearing on the same tree several seasons running, thereby increasing the possibility of such diseases.
Control is always worthwhile.
Infestations are easily removed by rubbing with a cloth or old toothbrush. Alternatively, use an insecticide. A systemic spray works best, as it enters the sap and is taken in by the feeding aphid. A contact spray has to penetrate the waxy fluff before it can reach the aphids, so it is less effective. Ask our experts for their advice or read their comments about controlling pests and diseases .