What are Cooley Spruce Galls?
Cooley spruce galls are common and conspicuous on blue spruce. They are aesthetically displeasing to many homeowners, although they do little or no harm to the tree. The galls are produced by aphid-like insects, the Cooley spruce gall adelgids. Once the galls begin to form, insecticides usually are ineffective because the insects are protected within the galls.
How to identify a Cooley Spruce Gall?
Cooley spruce galls are commonly found on the new growth of spruce trees. These galls are produced by Insects called Cooley spruce gall adelgids (woolly aphids). Galls appear early in the season as 2- to 4-inch cucumber-shaped growths. The galls are light green during late spring and early summer but dry out and become brown starting in mid-July. The galls often are mistaken for seed cones.
Cooley spruce galls are conspicuous and frequently cause considerable concern to homeowners. However, the galls usually do not cause any serious harm to the tree. Aesthetics are usually the main concern and reason for treatment, however extremely heavy infestations may cause minor retardation of tree growth and some distortion. In some cases chemical control can be applied in the early spring just before bud break to gain control the the pest.