Spring attacks are unimportant. Large colonies may develop in the shoots in summer, causing considerable leaf curl, stunting and shoot tips may be killed.
- This damage is important on nursery stock and young trees. In established orchards, infestation of up to 10% of shoots can be tolerated (see ‘Monitoring’).
- However, if colonies are large, fruit beneath may be contaminated with honeydew and cast skins.
- Colonies are usually attended by the common black ant Lasius niger, which feeds on the honeydew produced by the aphids and helps to prevent contamination of the foliage.