Red Balls on Maple Leaves: Eriophyid Mite Galls, Not Disease

Tiny raised red balls on Autumn Blaze maple leaves are galls caused by eriophyid mites—microscopic relatives of spiders. They’re unsightly but don’t harm tree health.

What They Are

• Mites inject growth-regulating chemicals → plant forms gall around them.
• Species: maple bladdergall mite, spindle gall mite, erineum gall mites.
• Colors: bright red, green, black.

No Treatment Needed

Tree vigor unaffected. Photosynthesis slightly reduced only in heavily galled leaves. Populations fluctuate yearly.

If You Want to Reduce Next Year

Spray carbaryl (Sevin) or chlorpyrifos (Dursban) on lower leaf surfaces when leaves are 1/4 expanded, repeat in 10 days. But rarely justified.

Won’t Spread

Mites are host-specific. Flower garden at base is safe.