Leaves are covered with white, cottony masses. Underneath the white masses are clusters of small (1/8 inch), purplish brown soft-bodied insects. The leaves are curled, distorted, and yellowing, and the tree is often weak and growing poorly.
Leaves are covered with white, cottony masses. Underneath the white masses are clusters of small (1/8 inch), purplish brown soft-bodied insects. The leaves are curled, distorted, and yellowing, and the tree is often weak and growing poorly.
(Eriosoma species)
Several species of woolly aphids attack elm throughout the country. When present in large numbers, they are both unsightly and severely damaging to the leaves. The aphids overwinter as eggs in bark crevices. The eggs hatch in spring as the elm leaves unfold. The aphids crawl to the undersides of the leaves to feed on plant sap. They cover themselves with a white, cottony mass as they feed. At the end of June, a generation of winged aphids may develop. They often leave the elm tree and fly to one of their summer hosts, such as apple, serviceberry, pyracantha, hawthorn, or mountain ash. In the fall, these aphids return to elms and lay the overwintering eggs.
Spray with an insecticide containing acephate when insects are first noticed in the spring. Cover the undersides of the leaves thoroughly. Repeat the spray 7 to 10 days later if damage continues.
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