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 needle midge
Photo by: R.S. Byther
  
Douglas Fir : Douglas fir needle midge
(revision date: 4/23/2014)


Biology
The tiny white larvae of the Douglas fir needle midge mine the inside of needles, which become yellowed and distorted. Infested needles often have a sharp bend at the injury site. Three different midges infest Douglas fir: one species feeds near the needle base, one feeds near the tip of the needle, and the third feeds near the middle. Damaged needles often drop from the tree, and heavy midge infestations can cause severe defoliation. The midges pupate in the ground, with the adults emerging around bud-break in the spring. The adult Douglas fir needle midge is a small fly. This can be a serious pest in Christmas tree plantations.
Management Options


Non-Chemical Management
  • Where practical, prune out heavily infested twigs.
  • Use emergence traps on the ground to catch adults. This will help determine the need for control. Contact your county Extension agent for further information.
Select non-chemical management options as your first choice!

Chemical Management

Control must be applied during budbreak. 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
  • This list may not include all products registered for this use.
Images

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Caption: Douglas-fir needle midge
Photo by: R.S. Byther