Green to yellow-green galls appear on the leaves, shoots, and nuts. These galls, which range in size from 1/8 to 1 inch in diameter, split open in the late spring. Shoots with galls on them may be weak and dying. When the galls are cut open, tiny, soft-bodied insects may be seen inside.
Once galls have formed, the insects cannot be killed. Appy an insecticide that''s labeled for these pests, following label directions.