NC State Extension Publications

Description and Biology

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The woolly apple aphid, Eriosoma lanigerum, is a pest native to North America, but it has spread widely throughout apple growing regions of the world. Woolly apple aphids resemble mealybugs because they secrete a white, fluffy substance that completely covers their bodies. Woolly apple aphids congregate on the stems of crabapple and pyracantha in dense, spectacular masses. However, these pests cause most damage to the roots where they cause galls that resemble those caused by root knot nematodes. Some of the aphids migrate to the upper parts of apple, crabapple and pyracantha where they overwinter on scars, callous tissue and rough places in the bark. Some of the aphids migrate to elms where the winter is spent as eggs on the bark. In the spring these eggs hatch, and the aphids cause galls on elm leaves. The next generation on elm develops wings and flies back to apple, cotoneaster, crabapple, and pyracantha where most crawl down to the roots to feed.

Woolly apple aphid damage to elm leaves.

Woolly apple aphid damage to elm leaves.

A wingless woolly apple aphid on cotoneaster twig.

A wingless woolly apple aphid on cotoneaster twig.

A mass of woolly apple aphids on cotoneaster.

A mass of woolly apple aphids on cotoneaster.

Another view of woolly apple aphids on cotoneaster.

Another view of woolly apple aphids on cotoneaster.

Woolly apple aphids on apple seedling.

Woolly apple aphids on apple seedling.

Host Plants

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Although the aphids cause alarm on the stems of apple, cotoneaster, crabapple, or pyracantha, woolly apple aphids cause most damage to the roots of these plants where they cause galls to form that resemble those caused by root knot nematodes. On elm, woolly apple aphids cause leaf galls inside of which they multiply.

Residential Recommendation

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Because woolly apple aphids migrate from elm each spring, it is almost impossible to prevent a suseptible plant from becoming infested. Probably the best way of coping with the woolly apple aphid is to try to keep infested plants as healthy as possible (fertilize according to a soil test, prune properly, mulch, and water during prolonged dry spells). In case of a heavy infestation of woolly apple aphids, it is probably wise to treat with some sort of pesticide. Several pesticides are labeled for aphids but I recommend one of the insecticidal soaps or horticultural oils for control of aphids above ground. Because these aphids damage roots, consider applying imidachloprid granular or drench or some other systemic insecticide labeled for home landscape use.

References

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For assistance with a specific problem, contact your local Cooperative Extension Center.

This Factsheet has not been peer reviewed.

Author

Professor Emeritus
Entomology and Plant Pathology

Publication date: July 13, 2013
Revised: Oct. 23, 2019

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