What is causing our maple trees to have black spots on the leaves?


Our maple trees have big black spots on the leaves. My guess is it’s a fungus; is that likely?  For now, assuming it’s a fungus, what’s the best product to treat it with? The maples are fairly new and small, so spraying would be possible.

oak with infected leaves
Photo used with permission from the client.


Kate Garland, Horticulturist

From what I can see, it appears to be a type of white oak tree with anthracnose. This has been a “good” year for anthracnose, which thrives in cool, wet spring weather. Here’s a helpful fact sheet that outlines the disease and management strategies: https://extension.umn.edu/plant-diseases/anthracnose-trees-and-shrubs

A few quick facts to note from the linked resource:

  • Anthracnose is a common fungal disease of shade trees that results in leaf spots, cupping or curling of leaves and early leaf drop.
  • . . .  is most common in cool, wet spring weather.
  • Anthracnose is not a significant threat to the health of the tree and doesn’t require treatment in most cases.