WSU Extension

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Poplar : Poplar petiole gall aphids
(revision date: 2/14/2019)


Biology
Aphids which cause galling of the leaf stem (petiole) are small, soft-bodied insects. The females lay eggs on tree bark in the fall. The eggs hatch in the spring, and the aphids move to and feed on the petioles, which react by enlarging and enclosing the insects. The hard, pale green, rounded galls form along the petiole or at the base of the leaf. Aphids inside the galls are grayish and waxy in appearance. The leaves are not damaged, but may be turned at right angles to the petiole. Aphids emerge from the galls in midsummer and fly to a summer host, where they feed on roots until fall. The aphids cause little damage to poplars, but may be serious pests on alternate hosts such as lettuce.
Management Options

Non-Chemical Management
  • Hose aphids from trees in fall with a strong stream of water.
  • Natural enemies of aphids such as ladybird beetles, syrphid (hover) flies, green lacewings, and others help control aphid populations. Avoid use of broad-spectrum insecticides which kill these beneficial insects.
Select non-chemical management options as your first choice!

Chemical Management

Apply to foliage in early spring before gall reaction becomes widespread. Homeowners should not make foliar applications to trees over 10 ft tall. Consult a commercial pesticide applicator for treatment of trees and shrubs over 10 ft. tall.

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Caption: Poplar petiole gall aphid
Photo by: A.L. Antonelli