Woolly Aphids

— Written By N.C. Cooperative Extension

The extension office has experienced a large number of calls asking about those little white fuzzy critters on their trees and shrubs.  Those little critters are known as woolly aphids.  These particular aphids occur on many hardwood and coniferous tree and shrub species in North Carolina, including Maple, Elm, Apple, Pear, Pine, Spruce, and Hawthorn.  They are small 1/8 inch in length; pear shaped insects and are often covered with white waxy strands.  The wax gives this pest a fluffy, cottony appearance, as though they are covered with wool.
 
Woolly aphids feed by inserting needle-like mouthparts into plant tissue and withdrawing sap.  They feed on leaves, buds, twigs, and bark, but can also feed on the roots.  Symptoms of feeding include twisted and curled leaves, yellowed foliage, poor plant growth, low plant vigor, and branch dieback.  Physical injury will result when larger numbers of woolly aphids attach to young trees or unhealthy, stressed trees.  Fortunately, severe woolly aphid infestations only occur periodically and are generally kept in check by natural enemies.  In addition to the physical damage to the plant, accumulations of wax and shed skins are sometimes very conspicuous signs on the leaves, twigs, and bark.

As a result of feeding on the sap, woolly aphids produce a sweet, sticky waste product called honeydew.  If often coats leaves, bark, and objects beneath the tree, giving them a shiny appearance.

Natural biological controls, such as lacewings, lady beetles, and parasitic flies normally keep wooly aphid populations below numbers that rarely damage trees.  Try to tolerate damage or presence on trees and shrubs.  Populations of woolly aphids rarely get to levels that harm plants despite the appearance of distorted leaves.  If the infestation is small and if it is practical, prune out and destroy the infested branches.  Insecticides are effective in reducing aphid numbers.  Systemic insecticides, such as acephate effectively manage woolly aphids.  Contact insecticides and insecticidal soap are ineffective because they do not penetrate through curled leaves or wax.  Affected leaves remain curled and distorted even when woolly aphids are successfully managed.

For more information about woolly aphids contact Mary Hollingsworth at the Hoke County Cooperative Extension Service at 910-875-3461.

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