WSU Extension

Hortsense

Douglas Fir : Cooley spruce gall adelgid
(revision date: 3/10/2017)


Biology
This aphid-like insect feeds on newly growing needles. Adelgids appear as woolly or cottony tufts on the needles, with heavily infested trees appearing "frosted" or flocked. Small purplish insects are found underneath the cottony tufts. Adelgid feeding can cause needles to become distorted or bent and yellowed. Infested needles sometimes drop prematurely. This pest is a serious concern in Christmas tree plantations, but is less important in the landscape. Cooley spruce gall adelgids also infest spruces, but cause distinctive galls on spruce that are not seen on Douglas fir. Chemical control must be aimed at crawlers during or shortly after bud-break.
Management Options

Non-Chemical Management
  • Planting spruce and Douglas fir trees as far apart as possible may help reduce adelgid infestations.
  • Hand-wipe to control minor infestations (where possible).
Select non-chemical management options as your first choice!

Chemical Management

Apply to control crawlers when new tips are expanding. Esfenvalerate is toxic to bees. Do not apply products containing esfenvalerate on or near blooming plants. To minimize risk to bees, apply in the evening after bees have stopped foraging for the day. 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.
  • Monterey Bug Buster II
    Active ingredient: esfenvalerate  |  EPA reg no: 1021-1778-54705
  • Ortho Bug B Gon Systemic Insect Killer Conc.
    Active ingredient: acetamiprid  |  EPA reg no: 8033-107-239
  • This list may not include all products registered for this use.
Images
    - hide images

+ Show larger images

 
Caption: Douglas-fir Cooley spruce gall adelgids
Photo by: A.L. Antonelli
Caption: Douglas-fir Cooley spruce gall adelgid hatchling
Photo by: C.R. Foss