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Phyllosticta Leaf Spot on Japanese Maple: Cosmetic Late-Season Fungus

Circular tan spots with purple-red borders and black fruiting bodies in rings on Japanese maple leaves are Phyllosticta leaf spot. Infection occurs late in the season; damage is minimal—leaves may drop slightly early.

Management

No treatment needed for established trees; tree health unaffected.
If desired, apply preventive fungicide (mancozeb, chlorothalonil) at bud break next spring.
Rake and destroy fallen leaves to reduce spores.
Fertilize to maintain vigor; cosmetic spots are not a health threat.

This is one of the most common and least damaging maple leaf spots.

Plant Diseases: Maple Leaf Warts and Holes: Phyllosticta Leaf Spot; White Spots on Red Maple: Superficial Fungus/Algae, Not Harmful; New Japanese Maple Brown Leaf Spots: Phyllosticta Leaf Spot; Japanese Maple Leaf Scorch and Transplant Shock: Same Symptoms, Different Causes; Phyllosticta Leaf Spot on Maple: The 'Lunar Eclipse' Fungus; Japanese Maple Leaf Spots: Phyllosticta (Purple Eye); Japanese Maple Leaf Spots: Phyllosticta Leaf Spot Diagnosis and Management; Valuing a Damaged Dwarf Japanese Maple: Need Certified Arborist Appraisal; Phyllosticta Leaf Spot on Young Maple; Minor Leaf Spots on Young Japanese Maple

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