Spruce: Cooley spruce gall adelgid

Biology

This aphid-like insect feeds at the base of newly growing needles. The plant responds to adelgid feeding by forming a green or purplish cone-shaped gall around them. This 1⁄2″ to 3″ gall turns brown and woody by midsummer or fall and the branch tips usually die. Overwintering adelgids appear as woolly clumps at the base of buds in fall, winter, and early spring. Cooley spruce gall adelgids also infest Douglas fir, but do not form galls on that plant.

Management Options

Use Integrated Pest Management (IPM) for successful plant problem management.

Non-chemical Management

Select non-chemical management options as your first choice!

• Planting spruce and Douglas fir trees as far apart as possible may help reduce (but not prevent) adelgid infestations.
• Galls may be pruned out to improve the short-term appearance of infested trees. Long-term pruning may ruin tree’s shape.
• Most spruce species in the Pacific Northwest are susceptible.

Chemical Management

IMPORTANT: Visit Home and Garden Fact Sheets for more information on using pesticides.

None recommended

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