Pest description and damage The adult beaked-gall midge is a small black fly. The larvae are about 0.2 inch long when mature. The adult midge lays eggs on buds in the spring, and the larval tunneling and feeding of the larvae causes the bud to swell and harden. By summer, it develops a characteristic shape and a reddish color. Infestations are rarely seriously injure a tree, but successive years of high infestations can alter the appearance of the plant, much as if the plant were excessively pruned. Pussy willow (Salix caprea) is reportedly a favorite host species.
Biology and life history The insect overwinters as a partly developed larva in the gall. In spring, the adults emerge, mate, and the females lay eggs on swollen willow buds. The emerging larva tunnels into the bud and causes gall formation. The larva develops inside a hollow cavity in the gall, which by September is hardened and red. There is one generation per year.
Prune out willow-beaked galls as they are noticed. If you prune them out in the fall or winter, be sure to destroy them by crushing or burying. The adults probably will still emerge if the galls are thrown to the ground.
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