Blister mite

Raised, blister-like bumps on leaf surfaces, often reddish or yellowish green, indicate blister mite feeding inside the leaf tissue. You will see these galls appearing on fruit tree and ornamental leaves from mid-spring onward as overwintering mites emerge from bud scales and begin feeding on expanding leaves. The blisters eventually turn brown or black as the season progresses.

Dormant oil applied during late winter before bud break smothers overwintering mites under bud scales. Once mites are inside the leaf blisters, they are protected from contact sprays. Damage is almost always cosmetic on established trees and does not affect overall plant health. Predatory mites help suppress populations naturally through the growing season.