WSU Extension

Hortsense

Douglas Fir
 
Disease
Armillaria root rot 
Laminated root rot 
Rhabdocline needle cast 
Rust 
Stem cankers 
Swiss needle cast 
Upper stem canker 
Yellow-green mottle syndrome 
Insect
Aphids 
Coneworms 
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 silverspotted tiger moths
Photo by: A.L. Antonelli
  
Douglas Fir : Silverspotted tiger moth
(revision date: 4/20/2015)


Biology
The caterpillars of the silverspotted tiger moth feed on the needles, often "tenting" branches with dirty-looking webs. Feeding occurs through fall and winter, with webs becoming more noticeable by spring. The caterpillars can reach 1 1/2" in length and are mostly reddish-brown with some blue-black or yellowish hairs. Adult moths are brownish or tan with distinct silver-white spots on the wings. Minor infestations cause little harm to trees. Douglas fir is the preferred host, but the caterpillars will infest other conifers. Caterpillar hairs can cause skin irritation if they are handled without gloves.
Management Options


Non-Chemical Management
  • Prune and destroy "tents" with caterpillars.
  • Hand-pick (wearing gloves) individual caterpillars.
Select non-chemical management options as your first choice!

Chemical Management

Apply when caterpillars first appear or when damage is noticed in late fall or early spring. If Bt is chosen, be sure to apply when insect is feeding. Best time 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.
  • 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.
Images

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Caption: Douglas-fir silverspotted tiger moths
Photo by: A.L. Antonelli
Caption: Douglas-fir silverspotted tiger moth: close-up
Photo by: L.W. Getzin