WSU Extension


Douglas Fir
Armillaria root rot 
Laminated root rot 
Rhabdocline needle cast 
Stem cankers 
Swiss needle cast 
Upper stem canker 
Yellow-green mottle syndrome 
Cooley spruce gall adelgid 
Douglas fir needle midge 
Douglas fir tussock moth 
Douglas fir twig weevil 
Sequoia pitch moth 
Silverspotted tiger moth 
Spruce spider mite 

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Caption: Douglas-fir tussock moth
Photo by: R.D. Akre
Douglas Fir : Douglas fir tussock moth
(revision date: 4/20/2015)

Douglas fir tussock moth larvae start at branch tips at the top of the tree and work down, feeding mainly on the new foliage and causing severe defoliation. They may be found under webbing on the branches. Severe tussock moth outbreaks are very sporadic and last usually around three years before subsiding. The larvae feed on the needles of Douglas fir, spruce, pine, larch, and true firs. They feed mainly on forest trees and are infrequent pests in the landscape. The caterpillars are distinguished by three long tufts of black hairs on their body (two in front, one in back) and lighter tufts along their back. The hairs from tussock moth caterpillars break off easily and may cause skin or respiratory irritation.
Management Options

Non-Chemical Management
  • Parasites and other natural controls keep this pest in check most of the time.
  • Prune and destroy (burn, if possible) heavily infested branches.
  • Do not touch caterpillars with bare hands. Hand-pick caterpillars only with gloves.
Select non-chemical management options as your first choice!

Chemical Management

Monitor trees and apply when caterpillars first appear. 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
  • Safer Brand Caterpillar Killer for Trees, Shrubs & Vegetables Conc II [Organic]
    Active ingredient: Bacillus thuringiensis subsp. kurstaki  |  EPA reg no: 70051-106-42697
  • Safer Brand Caterpillar Killer/Trees, Shrubs, & Vegetables Conc
    Active ingredient: Bacillus thuringiensis subsp. kurstaki  |  EPA reg no: 42697-23
  • This list may not include all products registered for this use.

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Caption: Douglas-fir tussock moth
Photo by: R.D. Akre