Michigan State University Extension
Ornamental Plants plus Version 2.0 - 00001097
01/01/98
Two adelgids commonly attack spruce. Eastern spruce gall adelgid forms pineapple like galls at the base of twigs. Galls caused by Cooley's spruce gall adelgid look like miniature cones at the branch tips. The adelgids do not kill trees unless the infestation is heavy. A few galls on a large tree are not serious.
Bagworms make a sack by webbing needles together. Small numbers may be picked off by hand.
Spruce budworm larvae feed on developing buds and young needles. The yellowish brown caterpillars are difficult to see.
The spruce needle miner makes a small hole in the base of a needle then mines out the center. Dead needles are webbed together and can be found on infested twigs.
Pine needle scale is a white, elongated scale.
Spider mites can be problem in summer after hot dry weather. The small insects can't be readily seen with the naked eye. The first noticeable symptoms are yellowing of the oldest needles on infested branches. Close inspection with a magnifying glass will confirm the presence of the mites.
Sawfly larvae may feed on the needles. One infestation will usually not kill the tree.