University of Illinois Extension
University of Illinois Extension - Selecting Trees for Your Home
Spruce Gall Adelgids
Adelges cooleyi, Adelges abietis
Severity: 2 out of 5
Frequency: 2 out of 5
Symptoms: The Cooley Spruce gall tends to go out to the tip of the shoot. The shoot may curve as a result of the gall being on only on side of the shoot. The entire new shoot may be one long gall too. On the spruce, galls are evident. On Douglas fir, there is no gall, but severe infestation does cause yellow spots to appear on the needles. Eastern spruce gall adelgid galls look like a tiny pineapple near the base of the shoot.

With the Cooley Spruce gall adelgids, the immature female overwinters and maturesin the spring. She lays several hundred eggs on side branches. After the eggs hatch, the young migrate to the base of needles on the new growth. The feeding induces the plant to envelope the individual adelgids as a group, thus forming a gall. By late June to July, the adelgids emerge from the galls. The females become winged and fly to Douglas fir or other spruces. Several life cycles later, and through most of another growing season, the adelgids return to the spruce trees. It takes two full growing seasons for the adelgids to make one complete cycle between both hosts.

The Eastern spruce gall adelgids overwinter as immature females, the females mature in the spring and lay between 100 and 200 eggs next to buds ready to open. The young feed on needles and eventually move to the base of the needles. A gall develops. After leaving the galls in late June to early July, the Eastern spruce gall adelgids become mature flying females. She lays her eggs in unprotected masses near the tips of needles. The cycle then starts again.

Management: Apply a recommended insecticide in late September or in spring just before bud break. Dormant or summer oils will turn "blue" spruces green untill the following year when new growth emerges.
Associated trees: