Cooley Spruce Gall Adelgid damage to spruce Michigan State University Extension Service	Cross-section showing insect development  Colorado State University Extension Service

The immature female Cooley spruce gall adelgids overwinter on spruce trees. The female matures in the spring and lays eggs on the branch tips. The eggs hatch and nymphs move to the new growth and feed at the base of the needles. The feeding causes formation of a gall that encloses the insects. In midsummer an opening forms at the base of each needle on the gall. The insects leave the gall through these openings and become winged females. They fly to Douglas fir or a spruce and feed on these trees as though they were woolly aphids. 

The most visible symptom is the galls formed at the branch tips. The branch tips appear to have swollen and drooped. They are sometimes described as small 'cones'. 

Use diazinon, Sevin, malathion, Orthene, or dormant oil. Sprays must be applied before the insects are enclosed in the gall. 

Information provided by the Michigan State University Extension Service

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