Galls are abnormal growths on a part of the plant. They can be caused by bacteria, insects, mites and fungi. They can be on any part of a plant and are the overgrowth of plant tissue in response ...

— Deb Schultz, Evanston The pinkish-red spots on your birch’s leaves appear to be erineum patches, which are a type of gall caused by very tiny eriophyid mites feeding on the leaf tissue. You ...

Erineum galls on birch leaves. These mites overwinter on the tree and begin feeding on the leaves in spring as they begin growing. There is generally no need to either treat erineum patches or the ...