WSU Extension

Hortsense

True Fir : Balsam twig aphid
(revision date: 2/14/2019)


Biology
Balsam twig aphids feed on needles and buds of firs. Three distinct forms of the balsam twig aphid occur. Aphids may be (1) small and yellow-green, (2) large and bluish-gray, or (3) have woolly white secretions which make them appear powdery. The aphids mat needles together and cause new growth to be deformed and stunted. Some needles are killed and drop from the tree, leaving rough twigs. A large amount of honeydew (a sticky material excreted by the insects) is produced, which may be covered with a black growth of sooty mold. Healthy trees will tolerate moderate infestations easily.
Management Options

Non-Chemical Management
  • Provide proper plant culture. Healthy plants can tolerate more insect damage.
  • Avoid overfertilization. High levels of nitrogen in the foliage encourages aphid reproduction. Switch to a slow-release or low-nitrogen formula if necessary.
  • Hose infested trees with a strong stream of water to wash off insects.
  • Prune and destroy individual, heavily-infested branches.
  • Encourage natural aphid predators, including ladybird beetles and green lacewings. Avoid use of broad-spectrum insecticides which can kill beneficial insects.
Select non-chemical management options as your first choice!

Chemical Management

Apply in spring. A second application may be needed in June. 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.

Listed below are examples of pesticides that are legal in Washington. Always read and follow all label directions.
  • Bonide Systemic Insect Control
    Active ingredient: acephate  |  EPA reg no: 239-2461-4
  • R-T-U Year-Round Spray Oil
    Active ingredient: oil/pet distillate  |  EPA reg no: 6218-78
  • Safer Brand BioNEEM Multi-Purpose Insecticide & Repellent Conc [Organic]
    Active ingredient: azadirachtin  |  EPA reg no: 70051-6-42697
  • Safer Brand BioNEEM Multi-Purpose Insecticide & Repellent Conc [Organic]
    Active ingredient: azadirachtin  |  EPA reg no: 70051-6-42697
  • Safer Brand Insect Killing Soap Conc II [Organic]
    Active ingredient: potassium laurate  |  EPA reg no: 42697-60
  • This list may not include all products registered for this use.
Images
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Caption: Balsam twig aphid
Photo by: A.L. Antonelli