Maple Spindle Gall Mites: Cosmetic Leaf Galls

A healthy sugar maple shows small, green-to-beige, spindle-shaped projections on upper leaf surfaces. The owner wonders if this gall-like growth indicates disease.

Diagnosis: Maple Spindle Gall

Caused by the eriophyid mite Vasates aceris-crumena, these galls form when mites feed on developing leaves, triggering abnormal plant tissue growth. Galls are ~1/5 inch long, pencil-lead thickness, tapering at both ends—distinctive and easily identified.

Life Cycle and Impact

Mites overwinter under bark scales near scars and broken branch ends. Spring feeding initiates gall formation. While conspicuous, galls cause minimal harm—primarily aesthetic. They don't significantly reduce photosynthesis or tree vigor.

Management

• No treatment needed for established trees.
• For young, recently transplanted specimens, consider dormant oil applications if aesthetics are paramount.
• Prioritize cultural health: proper watering, fertilization, and mulching.

Gall abundance varies yearly. Efforts are better spent on overall tree vitality than gall eradication.