Kelly Jackson
Christian County Extension Office
Woolly Aphids
Elm, silver maple, apple hawthorn, and serviceberry often have colonies of woolly aphids living on the undersides of their leaves in spring. Initially, they are clearly aphids but they take on a fluffy appearance later in their development due to white, waxy strands that they secrete. The adornments protect them from predators and may help them to move.
Woolly aphids are sap feeders. Depending on the species, they may feed on leaves, buds, twigs, bark, or roots. Saliva injected while the aphids feed may produce twisted, curled, or yellowed leaves, and/or poor growth. Honeydew, the sticky liquid waste produced by these aphids, can support the growth of sooty mold fungi, which blacken surfaces on which the droplets land.
Woolly aphids cause some unsightly symptoms on foliage but rarely affect established, healthy trees and shrubs. These insects mainly produce aesthetic damage, such as distorted leaves. Distorted leaves are only a cosmetic issue; they generally do not affect long-term tree or shrub health. In addition, the aphids will leave their spring hosts and migrate to summer hosts. By the time damage is noticed, the aphids may be ready to take flight. Finally, the waxy filaments secreted by the aphids can reduce the effectiveness of contact insecticides.