Red Maple Leaf Spots vs. Galls: Identify Before Treating

Two Possibilities

Fungal leaf spots — small, defined lesions; treat with fungicide at bud break.
Insect galls — raised, hollow structures; no treatment needed.

Compare photos to OSU fact sheets (links in original). Both are cosmetic; neither kills the tree.

Trees: Red Maple Bark Splitting: Frost Cracks, Lichens, and Decline Risk; Red Bumps on One Maple Only: Insect Galls, Not Disease; Phyllosticta Leaf Spot on Japanese Maple: Cosmetic Late-Season Fungus; Silver Maple Base Sprouts Only: Root Stress and Canopy Loss; Red Maple Borer Infestation: Sap Flow and Bud Failure; Red Maple Leaf Galls: Harmless Insect-Induced Growths; Diagnosing Maple Leaf Scorch: Bacterial vs. Physiological; Red Maple Leaf Tip Burn: Nutrient Deficiency or Herbicide?; Maple Bladder Galls: Cosmetic Mite Damage; Beaver Damage to Dwarf Japanese Maple: Girdling Assessment

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