WSU Extension

Hortsense

Caption: Spruce budworm
Photo by: T.J. Fitzgerald
  
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True Fir : Spruce budworm
(revision date: 4/20/2015)


Biology
These larvae feed on the buds and foliage and may tie shoot tips together with webbing to make a nest. They are typically green to brown in color with a darker head and grow to approximately 1" in length. The adult is a dark gray moth. Spruce budworms are mainly pests of balsam and subalpine firs. They also attack spruces and Douglas fir. This insect is an infrequent pest in the landscape.
Management Options

Non-Chemical Management
  • Hand-pick and destroy on small trees (where possible).
  • Avoid use of broad-spectrum insecticides which may kill natural predators and parasites including parasitic wasps.
Select non-chemical management options as your first choice!

Chemical Management


Apply insecticides in spring (May) when larvae are feeding on old needles and before they enter buds. June to July applications will control larvae on new growth. If Bt is chosen, be sure to apply when insect is feeding. The best time to apply is when caterpillars are young. Use a spreader-sticker with liquid Bt formulations. 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.
  • 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: Spruce budworm
Photo by: T.J. Fitzgerald