True Fir: Balsam woolly adelgid

categories: Conifers Ornamentals True Fir True Fir Insects

revision date: 2023-02-07 12:00

Shown on a black background swollen, knob-like areas at nodes and tips of infested branches can be seen.
Balsam woolly adelgid damage
Photo by: R.S. Byther


The balsam woolly adelgid feeds on the stems of true firs. White or grayish cotton-like masses, inside which are the purplish-black insects, can be found on the twigs, branches, or trunk. Heavy adelgid infestations may cover the entire trunk. The feeding insects cause the tree to form swollen, knob-like areas at nodes and tips of infested branches. Adelgid infestations weaken trees, cause foliage to become sparse, and can kill trees. This is a serious pest in the forest and the landscape on balsam, grand, subalpine, Pacific silver, and Frasier firs. Balsam fir and subalpine fir are particularly susceptible.

Management Options

Use Integrated Pest Management (IPM) for successful plant problem management.

Non-chemical Management

Select non-chemical management options as your first choice!

  • Hand-wipe to remove minor infestations when possible.
  • Hose infested trees with strong stream of water to wash off these insects.
  • Ladybird beetles and syrphid fly larvae help control adelgid populations. Avoid use of broad-spectrum insecticides which will kill these important predators.

Chemical Management

IMPORTANT: Visit Home and Garden Fact Sheets for more information on using pesticides.

  • Control must be aimed at “crawlers”. In western Washington, this is usually in spring around the end of April to early May.
  • These products are toxic to bees.
  • Do not apply any of the products listed on or near blooming plants.
  • To minimize risk to bees, apply in the evening after bees have stopped foraging for the day.
  • 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.

Approved Pesticides

Listed below are examples of pesticides that are legal in Washington. Always read and follow all label directions.

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