Cooley Spruce Gall

Cooley spruce gall adelgid, Adelges cooleyi, commonly causes abnormal growths called galls and distortion to the new needles of Colorado spruce and Douglas fir trees. Galls appear as small pineapple shaped growths early in the season. They brown out in the summer and can be confused with seed cones. The galls rarely cause serious harm and can be covered by new growth the following season.

Treatment Strategy

Cooley spruce gall adelgid can be tough to manage. Once the galls begin to form, insecticides usually are ineffective because the insects are protected within the galls. Systemic soil application should be made in late summer/fall because of the early spring activity of adults. The best times to spray are in the spring before new growth starts or in the fall when overwintering stages of the insect have returned to the tree.

Other Treatment Practices

  • Prune off and destroy galls during June or July before they open and adults emerge.

Soil Drench/Injection Using Xytect 2F

Soil Drench/Injection Using Xytect 75WSP

Basal Soil Drench or Basal Soil Injection or Systemic Basal Bark Spray Using Transtect

Foliar Spray Using Up-Star Gold

Expected Results

It is recommended that late summer/fall applications of Xytect be applied to control this early spring insect due to the possibility of an early spring infestation.

Signs of Damage

  • On spruces, pineapple-like formations (galls) are present on the tips of new growth
  • Galls turn brown during the summer months
  • Galls are not formed on Douglas fir, but needles may become discolored, distorted, and prematurely drop from the tree

Photo: Whitney Cranshaw
Colorado State University,

Photo: Whitney Cranshaw
Colorado State University,

Photo: Petr Kapitola
State Phytosanitary Administration,

Trees At Risk

  • Colorado spruce (Picea pungens)
  • Douglas fir (Pseudotsuga menziesii)


Cooley spruce gall’s life cycle is fairly complex, as it involves multiple biological forms. Three of these biological forms take place on spruce and two on Douglas fir. The complete life cycle through all five of these forms takes at least two years to complete. The pest’s life cycle can be completed on Douglas fir alone, but the forms that take place on spruce have to find Douglas fir as the second host to complete the entire life cycle.

On spruce:

  • Females feed in the spring and lay several hundred eggs.
  • Eggs hatch in 10-14 days.
  • Young nymphs move to new growth to feed at the base of the needles.
  • Feeding causes distorted gall formations that soon surround the young nymphs.
  • Galls dry out and brown by mid-summer.
  • Adelgids emerge from galls and move to Douglas fir or stay on the spruce.
  • Immature females overwinter at the base of terminal buds.

On Douglas fir:

  • Females that have migrated from spruce lay eggs on needles.
  • The following spring winged females are produced and they return to the spruce to start the life cycle over again.
  • Wingless females stay on the Douglas-fir and reproduce.

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A Treatment Guide is designed to help you identify common issues and management solutions. Comprehensive Treatment Guide PDFs, which include current products, application rates, and additional information, are available upon request.