My maple leaves have black tar-like spots. What is it and is it harmful?

Those raised, shiny black spots are tar spot (Rhytisma species), a fungal disease that's very common on maples — especially Norway, silver, and red maples. Despite its alarming appearance, tar spot is almost entirely cosmetic.

What you're seeing:

• Small yellow spots appear in early summer, then develop into raised, tar-like black blotches up to 3/4 inch across by late summer
• The spots are the fungal fruiting structures; they cannot be rubbed off
• Heavy infections can cause some early leaf drop, but they do not threaten the tree's long-term health

Management:

1. Rake and destroy fallen leaves in autumn — the fungus overwinters on leaf litter and reinfects in spring. This is the single most effective control.
2. Fungicides are rarely warranted for an established shade tree; by the time spots appear, it's too late to spray that season.
3. Keep the tree healthy with proper watering and mulching so it tolerates the minor stress.

Tar spot tends to be worse in wet springs and often improves on its own in drier years. Use our Diagnose tool if you want to confirm against other leaf-spot diseases.