University of Maryland Extension

Woolly Aphids - Trees

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woolly apple
Infestation of woolly aphids

Woolly aphids are aphids that produce a covering of fluffy white wax. One of the most common species found in landscapes is the woolly apple aphid (see photo above). It is most commonly found on crabapple feeding at the base of new shoots. It prefers to suck the sap from roots, branches and twigs of apple, but may also be found on alder, elm, mountain ash, hawthorn, serviceberry, and Pyracantha. Examine trees for bluish-black aphids covered with fluffy white wax on exposed roots, wounds on trunks and branches, and at the bases of new shoots on branches. 

Management

Parasitic wasps usually control woolly aphids. However, if necessary large infestations can be reduced by spraying with horticultural oil or insecticidal soap.

Other species of woolly aphids include the woolly elm aphid (elm, service berry as alternate host), woolly elm bark aphid (American and slippery elm), beech blight aphid (beech), and woolly alder aphid (alder and silver maple).

woolly alder on twigs
Woolly alder aphid

woolly hawthorne
Woolly aphids on hawthorn
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