Rainy summer weather creates high humidity, favoring fungal leaf spot diseases. These commonly affect sweetgum, poplar, and maple, though not all trees are infested—even adjacent trees may differ.
Leaf spots rarely cause serious harm. Trees can be completely defoliated one year and return healthy the next. For cultural control, rake and remove all fallen leaves in November and replace with clean mulch.
If the appearance truly bothers you, spray with Mancozeb, Kop-R-Spray, or chlorothalonil-containing products when spots first appear each year.
Red Bumps on One Maple Only: Insect Galls, Not Disease
Silver Maple Base Sprouts Only: Root Stress and Canopy Loss
Red Bumps on Maple Leaves? Harmless Gall Wasps — No Treatment Needed
Maple Spindle Gall Mites: Yellow Spikes Are Cosmetic
Thin-Leaved Orchids Dropping Leaves: Cold Stress and Root Rot
Japanese Maple Cold Damage: Will Leaves Return?
Maple Root Concerns and Hybrid Poplar Stump Control
Leaf Skeletonizing on Bloodgood Japanese Maple: Trumpet Skeletonizer or Minor Damage?
Bigleaf Maple Aphid Identification and Management
Silver Maple Leaf Drop: Maple Petiole Borer, Not Disease
Maple Seedling Care: Transplanting Timing and Leaf Spot Treatment
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