Woolly aphid on apple trees

The photo shows woolly aphids on old wounds on an apple tree.

What is Woolly Aphid?

Woolly aphid generally appears late summer/early autumn. It looks a bit like white fairy floss. This three-dimensional presentation is one of the things that distinguishes it from powdery mildew.

Woolly aphids are tiny grey or black aphids which produce a woolly or cotton-like covering. If you scrape back the white covering, on the branches, twigs and leaves, you will see these sap-sucking insects colonising these areas. They can cause knobbly formations especially on old wounds, as in the photo, and can also attack tree roots. In large numbers they are quite detrimental to tree health. While the most vulnerable trees are Pink Ladies, Jonathans and Granny Smiths, they can appear on any apple tree.

How do you control Woolly Aphid?

To control woolly aphid organically, spray with an insecticidal soap, neem oil or a horticultural oil. Make sure the spray penetrates to the wood. You can also scrub the branches by hand with water and a few drops of detergent if the infestation is small, and then spray. In winter after pruning, spray with lime sulphur as a preventative.

Written by Robin Gale-Baker