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Phyllosticta Leaf Spot on Red Sunset Maple: Spring Fungicide and Fertilizer

Yellow-green leaves with small brown spots on a 4-year-old red sunset maple are Phyllosticta leaf spot—a late-season fungus causing minimal damage. Spots won't disappear with treatment now.

Plan for Next Year

Apply preventive fungicide (mancozeb, chlorothalonil) at bud break and 2-3 times at 2-week intervals.
Fertilize with 10-10-10 at 1 lb per inch trunk diameter to green up foliage.
Rake leaves in fall; spots are cosmetic, not a health threat.

Focus on tree vigor; the disease is primarily aesthetic.

Plant Diseases: Japanese Maple Honeydew and Sooty Mold: Aphid or Scale Infestation; Red Sunset Maple Leaves Turning Brown: Causes and Solutions; Sunset Maple Bark Splitting and Leaf Spots: Need Photos for Diagnosis; Troubleshooting a Struggling Sunset Maple: Water, Nutrients, and Herbicide Risks; Glory Red Maple Leaf Browning in Florida: Transplant Shock vs. Drought; Sunset Maple Bare Branches: Normal Canopy Habit or Borer Swelling; Why 'Sunset' Maple Isn't Turning Red: Science and Solutions; Japanese Maple Leaves Turning Green in Summer; Japanese Maple Leaf Scorch: Recovery and Prevention; 'Bloodgood' Japanese Maple Leaf Scorch: Needs Shade

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