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Red Rash on Acer Leaves: Eriophyid Mite Galls, Not Disease

Brilliant Red Bumps on Maple Leaves Are Mite Galls

Your Acer brilliantissimum gets a “red rash” that shrivels leaves. These are galls caused by eriophyid mites (e.g., maple bladdergall mite, spindle gall mite). Mites inject growth regulators; plant forms galls that house and feed them.

Harmless but Ugly

Tree vigor not significantly affected.
Photosynthesis may dip in heavily galled leaves.
If you want fewer next year: spray carbaryl (Sevin) or chlorpyrifos (Dursban) on leaf undersides when leaves are ¼ expanded, repeat in 10 days.

No treatment needed for health—only aesthetics.

Trees: Walnut-Sized Galls on Pin Oak Branches: Twig Galls, Not Tree Killers; Spider Mites on Indoor Ivy: Move Outdoors and Treat; Aspen Leaf and Shoot Blight: Venturia Fungus Management in Wet Climates; Birch Leaf Galls: Mite-Induced Growths and Why Not to Worry; Bay Leaf Plant Leaf Spots: Identifying and Managing Shot Hole Disease; Maple Spindle Gall Mites: Yellow Spikes Are Cosmetic; Maple Leaf Galls: Identify Before Replacing Tree; Oak Galls on Scrub Oak: Woody Twig Galls; Identifying and Managing Oak Leaf Spots and Galls; Sumac Leaf Galls: Aphid-Created Structures on Volunteer Shrubs

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