Phyllosticta Leaf Spot on Young Maple

Diagnosis

Tiny red-dotted clusters on maple leaves each year are likely Phyllosticta leaf spot, a late-season fungal disease. It causes minimal harm—mainly early leaf drop.

Management

• Fungicides (mancozeb, chlorothalonil) applied at spring leaf-out can prevent new spots but won’t cure existing ones.
• On a small tree, spraying is feasible; on large trees, it’s usually not worth the effort.
• Rake and destroy fallen leaves to reduce inoculum.

The tree will outgrow the problem as it matures.