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Caption: Balsam woolly adelgid damage
Photo by: R.S. Byther
  
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True Fir : Balsam woolly adelgid
(revision date: 1/22/2016)


Biology
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

Non-Chemical Management
  • 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.
Select non-chemical management options as your first choice!

Chemical Management


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.

Listed below are examples of pesticides that are legal in Washington. Always read and follow all label directions.
  • GardenTech Sevin Conc Bug Killer
    Active ingredient: carbaryl  |  EPA reg no: 264-334-71004
  • This list may not include all products registered for this use.
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Caption: Balsam woolly adelgid damage
Photo by: R.S. Byther
Caption: Balsam woolly adelgids
Photo by: A.L. Antonelli