Woolly Elm Aphids

Woolly elm aphids alternates between the elm trees and saskatoon bushes. This insect overwinters on elm trees in the egg stage. They hatch and feed on the elm tree causing a rolled gall formation on the leaves. In late June they migrate to the saskatoon bushes, and attack the roots. In late July to August the colonies are evident. To determine whether the aphids are on the roots, remoe a bit of soil and check for white woolly or waxy material and small gray aphids. In the fall the winged female aphids migrate back to the elm trees. They give birth to more female and male aphids which mate, and each female lays an egg which overwinters on the elm tree.

Registered control methods are unavilable fro fruiting trees at this time. Control on local elms would be the use of dimethoate (Cygon 2-E). This can be painted on the bark of the tree just below the first lateral branch. The diameter of the band of dimethoate (1 – 2 inches) is relative to the diameter of the tree.

Do not spray dimethoate (Cygon) on Elms

By Dr. Paton and Vicki East