Picea: Eastern Spruce Gall Aphid

Problem
The ends of branches develop green, pineapple-shaped galls in the spring; in late summer, they turn brown and dry. Growth continues beyond the galls, but the branch may be severely stunted. Galled stems are weak and may break during storms. When large numbers of galls are formed, the tree may be less vigorous.

Analysis
(Adelges abietis)

This gall aphid is most damaging to Norway spruce, but may occasionally infest white, black, and red spruce. The insect spends the winter at the base of a terminal bud. When buds begin to grow in the spring, the aphids lay clusters of several hundred eggs that are covered with white, waxy threads. The young that hatch from these eggs feed on developing needles. They suck the juices from the needles, inducing the formation of galls that enclose them. The aphids live and feed in chambers inside the galls. In mid- to late summer, the galls turn brown and crack open. Aphids that emerge lay eggs near the tip of the needles. The young that hatch from these eggs spend the winter at the base of the buds.

Solution
Spray with an insecticide containing acephate, malathion, diazinon, or endosulfan in the spring just before growth begins, and again in the fall after the galls turn brown and crack open, around late September.