Leaf Galls on Oak: Cosmetic, Not Harmful

Diagnosis

Small "pimples" on fallen oak leaves in Brooklyn, NY are gall mite (eriophyid mite) galls. The mites lay eggs, inducing the leaf to form protective structures.

Impact and Management

• Not a health threat. Only causes premature leaf drop in late summer.
• Rake and destroy leaves to reduce next year's population.
• No spraying needed on a large mature oak.