Hawthorn Leaf Galls: Mite-Caused Cosmetic Bumps

Fuzzy Squiggles on Hawthorn Leaves: Eriophyid Mite Galls

A hawthorn (Crataegus spp.) in Edmonton (Zone 3b) with fuzzy squiggles on terminal leaves has eriophyid mite galls—cosmetic, not harmful.

Gall Facts

• Caused by microscopic mites (8 legs, not insects).
• Mite feeding triggers plant to form protective gall structure.
• Mites live/reproduce inside — protected from predators.
• Thousands of gall types exist — host-specific.

Management: Benign Neglect

• No chemical control needed — galls don't impact tree health.
• Fall sanitation: Rake/destroy leaves before spring bud break. Removes overwintering mites.
• Aphids on other leaves: Separate issue. Usually minor on hawthorn.

Why Terminal Leaves Only?

Mites colonize newest, most tender growth first. As leaves harden, they become unsuitable.

Cool photo! These galls are nature's architecture. Your hawthorn will be fine.