How to Manage Pests

Pests in Gardens and Landscapes

Woolly apple aphid—Eriosoma lanigerum

Adult woolly apple aphids have reddish to purple bodies and are completely covered with woolly white wax. Unlike other aphids, they primarily infest woody parts of trees.

Identification of species | Life cycle

Damage

Woolly apple aphids infest roots, trunks, limbs, and shoots, producing galls at the site of infestation. Root colonies cause swollen, nodular masses of gall tissue to form, stunting the tree. Aerial colonies are found in growth cracks, wounds, or at the axils of leaves on first- and second-year wood. Cankers and burs can develop on tree limbs.

Solutions

The parasite Aphelinus mali, with the help of other natural enemies, can completely control aerial colonies. Sprays of insecticidal soaps or horticultural oils may control light populations on limbs. Root-infesting populations cannot be controlled with pesticides. Where woolly apple aphid is a serious problem, consider resistant rootstocks, such as M111 or M106.

For more information, see the Aphids Pest Note.

Woolly apple aphid adults
Woolly apple aphid adults

Burs on limbs caused by woolly apple aphids
Burs on limbs caused by woolly apple aphids


Statewide IPM Program, Agriculture and Natural Resources, University of California
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