A number of small flies or wasps cause the formation on oak leaves or twigs. Lay eggs on the leaves or twigs. The plant then forms a gall in which the immature insect develops.
The galls that form on leaves are of little consequence to a healthy tree. However, the twig galls are more serious. The gall formation on the twig disrupts twig function and the portion of the twig beyond the gall may die. A tree heavily infested with twig galls may die.
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|Oak gall - 48K||Oak apple gall - 36K|
|Oak gall - 35K||Hedgehog gall on oak - 43K|
|Oak gall - 42K|