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 twig weevil on noble fir
Photo by: Unknown
  
Douglas Fir : Douglas fir twig weevil
(revision date: 3/10/2017)


Biology
The Douglas fir twig weevil is a small, wingless, grayish-black beetle with white markings and sometimes pinkish spots. The adult lays eggs in twigs in the summer. The larvae mine under the bark or inside twigs. Infested twigs and small branches often turn a reddish-brown and die back. Small, stressed trees are especially susceptible to attack by the weevils, particularly in dry years.
Management Options


Non-Chemical Management
  • Provide proper culture and minimize stress for trees, especially young ones. Healthy plants are more able to withstand insect feeding.
  • Prune and destroy infested twigs, burning where possible.
  • Hand-pick adults to control minor infestations on small trees, where practical.
Select non-chemical management options as your first choice!

Chemical Management

Apply in July to early August to seedling or small trees. 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.
  • Bayer Advanced Power Force Multi-Insect Killer R-T-S
    Active ingredient: cyfluthrin  |  EPA reg no: 72155-39
  • Monterey Bug Buster II
    Active ingredient: esfenvalerate  |  EPA reg no: 1021-1778-54705
  • This list may not include all products registered for this use.
Images

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Caption: Douglas-fir twig weevil on noble fir
Photo by: Unknown