Yellowish spikes on leaf tops, some brown = maple spindle gall mite (Vasates aceris-crumena). Mites overwinter under bark scales; induce spindle galls on new leaves.
None needed. Focus on watering/fertilizing for vigor. Spraying rarely justified except for high-value specimen or recent transplant.
Dry Pittsburgh summer may have increased mite activity. Good horticulture > pesticides.
Maple Anthracnose: Brown Veinal Discoloration—Cultural and Chemical Control
Red Maple Bark Splitting: Frost Cracks, Lichens, and Decline Risk
Phyllosticta Leaf Spot on Autumn Blaze Maple: Cosmetic, Not Critical
Bark Peeling on Mature Japanese Maple: Sunscald or Something Else?
October Glory Maple Leaf Scorch After Transplant: Stress, Not Disease
Japanese Maple Scale Infestation: Simple WD-40 and Oil Treatment
Walnut-Sized Galls on Pin Oak Branches: Twig Galls, Not Tree Killers
Maple Leaf Galls: Harmless Insect Structures, No Human Risk
Maple Spindle Galls: Cosmetic Only, No Treatment Needed
Maple Leaf Spot: Phyllosticta Diagnosis and Management
Identifying and Managing Oak Leaf Spots and Galls
Sumac Leaf Galls: Aphid-Created Structures on Volunteer Shrubs
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