Brown Spots on Maple Leaves: Phyllosticta Leaf Spot

A 30-year-old maple near Philadelphia shows brown spots with purple-red borders and black fruiting bodies in rings—classic Phyllosticta leaf spot (Phyllosticta minima). It infects late in the season, causing minimal harm.

Disease Profile

• Affects Amur, Japanese, red, silver maples.
• Spots: circular, tan with purple/red borders; black rings inside later.
• Causes early leaf drop but rarely impacts tree health.

Management

Fungicides rarely needed. For high-value trees:

• Apply labeled fungicide (mancozeb or chlorothalonil) in early spring as buds break.
• Repeat per label (usually 10–14 days) for 2–3 months.
• Rake and destroy fallen leaves before spring to reduce inoculum.

Large trees are hard to spray; focus on sanitation and tree vigor instead.