Print this fact sheet by W.S. Cranshaw* (6/13) Quick Facts… Cooley spruce galls are common and conspicuous on blue spruce. However, they do little or no harm to the tree. The galls are produced by aphid-like insects, Cooley spruce gall adelgids. Cooley spruce gall adelgids require two hosts to complete their normal life cycle: spruce … Continue reading Cooley Spruce Galls – 5.534