Two gall aphids commonly attack spruce. Eastern spruce gall aphid forms pineapple like galls at the base of twigs. Galls caused by Cooley's spruce gall aphid look like miniature cones at the branch tips. The gall aphids do not kill trees unless the infestation is heavy. A few galls on a large tree are not serious. Use malathion, Orthene or Diazinon applied in mid to late April or in late July just after the galls open.
Bagworms make a sack by webbing needles together. Small numbers may be picked off by hand. Use Bacillus thuringiensis, Diazinon, or malathion when the insects are small.
Spruce budworm larvae feed on developing buds and young needles. The yellowish brown caterpillars are difficult to see. Sprays of Orthene or Sevin control spruce budworm.
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. Use Orthene, Sevin, or Diazinon, when the insects are actively feeding, usually late April to early May and again in late July.
Pine needle scale is a white, elongated scale. Spray with Diazinon, Orthene, Sevin or malathion when crawlers are present.
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. Use Orthene according to label directions.
Sawfly larvae may feed on the needles. One infestation will usually not kill the tree. Sawfly larvae are controlled with Orthene.