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Powdery Mildew on Japanese Red Maple: Fungicide and Cultural Control

Gray/white deposits on upper branch surfaces and leaf edges = powdery mildew. It's a superficial fungus that reduces photosynthesis and aesthetics but rarely kills.

Control

Spray fungicide at first sign: triadimefon (Bayleton), triforine (Funginex), thiophanate-methyl (Cleary's 3336), or propiconazole (Banner).
Alternate fungicide classes yearly to prevent resistance.
Use spreader-sticker; cover both leaf surfaces.
Spray regularly, more often in cool damp weather.
Improve air flow, avoid overhead watering.

Early, consistent treatment gives best results.

Plant Diseases: Japanese Red Maple Post-Transplant Leaf Spots: Need Photo; Japanese Maple Spring Leaf Damage: Herbicide Injury vs. Winter Kill; Multiple Tree Decline: Red Maple, Rhododendron, Magnolia, Japanese Maples; Diagnosing Red Maple Decline: White Spots, Shriveling Leaves, and Fungus; Red Leaf Maple Dieback: Winter Desiccation and Canopy Restructuring; Japanese Red Maple Aphids: Atomic Grow for Cleanup and Vigor; Japanese Red Maple Brown Tips: Miracle-Gro Salt/Chlorine Toxicity; Japanese Maple Leaf Wither: Overwatering in Clay Soil Corrected by Deep Weekly Watering; Japanese Maple Leaf Scorch: Heat, Wind, and Root Moisture; Japanese Maple Leaf Scorch: Recovery and Prevention

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