Buckeye Yard and Garden onLine

On birch, the females move in the spring to newly expanding leaves where they feed, mature and give birth to a new crop of aphids. Aphid numbers expand quickly with each succeeding generation contributing to an ever-expanding aphid population. The feeding damage on birch causes the expanding leaves to pucker and bulge length-wise producing the characteristic leaf corrugations. The aphids cover themselves in a waxy, white, flocculent material and live on the underside of the leaves within the corrugations. The affected leaves will usually turn yellow and may prematurely fall off of the tree.

Eventually, the aphids on birch produce winged females that fly to witch-hazel. They lay eggs on the bark that will hatch into "stem mothers" the following spring. The stem mothers feed on newly expanding buds and inject chemicals that cause the buds to form a hollow, spiny, globular gall around their progeny. The winged aphids arising from the witch-hazel galls fly back to birch.

Damage to both plant hosts is usually not severe enough to warrant treatment, particularly on witch-hazel where the galls have little impact on plant health. Frequently, numerous predators will destroy aphid populations on the birch leaves. However, if heavy infestations on birch occur on highly visible plants, aphid populations can be reduced with a fall soil drench application of imidacloprid, or a spring topical application of acephate or insecticidal soap.