How to Manage Pests

Pests in Gardens and Landscapes

Woolly aphids

Woolly aphid adults are pear shaped, usually 0.13 inch or less in length, and cover themselves with white waxy material.

Identification of species

Damage

Some species feed in groups and cause swellings on bark or roots. Cankers and burs or burls can develop on limbs. On roots, nodular masses of gall tissue may form. Foliage-feeding species can cause infested leaves to curl, distort, discolor, or form into galls. Some species secrete honeydew, which results in growth of blackish sooty mold. Others produce pale waxy secretions, causing white flocculent material to collect on and beneath infested plants. Gall-making species may confine their honeydew or wax to within distorted tissue so this secretion is not obvious unless galls are cut open.

Solutions

Natural enemies and the parasite Aphelinus mali help to control aphids, but may not appear in sufficient numbers until aphids are abundant. If aphids cannot be tolerated and insecticides are deemed necessary, use materials such as insecticidal soaps and narrow-range oils. Oil and soap professionally applied with a high-pressure sprayer can provide some control. Homeowner application of these materials isn't highly effective. Spot treat where aphids are most abundant to preserve natural enemies elsewhere. Repeated soap sprays may wash away stickiness and exposed cast skins. Manage ants as they can disrupt biological control. Where aphids feed within curled leaves acephate can be used on ornamentals, but is toxic to natural enemies. Other controls have not been investigated.

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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