On spruce twigs, galls are formed in response to feeding by this pest. When infestations are heavy the resulting bud destruction may destroy the shape of the tree. The gall it forms on spruce is an elongate, pineapple-shaped green growth that develops on the tip of the current year’s twig . In late summer these galls turn brown. On Douglas-fir heavily infested needles appear to be covered with snow. No galls are formed on Douglas fir, but feeding by this species on the underside of needles may cause needle discoloration, needle distortion, and premature needle drop. Spray treatments recommended.