black spots on maple tree leaves

Asked June 4, 2018, 4:13 PM EDT

Two of my mature maples suddenly have black spots on the leaves. A number of years ago I lost a mature maple that had black spots on the leaves, although they were different. Everyone said that they wouldn't kill the tree, but they did. I think it was black tar spots. These spots are different, but I am concerned and want to act right away rather than risk losing 2 mature trees. Thank you very much.

Washtenaw County Michigan

3 Responses

These spots are from a fungal disease called anthracnose that is caused by the long periods of wet conditions in May. It is not something that can be treated for at this point and as we get into warmer and drier conditions in summer the spread of the fungus will stop. It is generally not a disease that is sprayed for since it takes just the right environmental conditions for the disease to spread. We see this yearly on many silver maples and those that are crossed with red maples but it is usually so minimal that it goes unnoticed. Usually the tree still has the majority of leaves and they continue to function and it has little impact on the tree. Maples continue for awhile to push out more leaves in early summer and these will likely not be impacted since the conditions are different from spring. One of our pathologists wrote an article on this topic in 2009 when conditions were very similar. Please click on the following link to read her article:

Thank you for your answer. That would seem to make sense. Although when I was looking it up the pictures of phyllosticta looked more like what my leaves looked like (to me at least). Is there a possibility it could be that?

I appreciate your help!

Anthracnose symptoms are a bit different and align mostly along veins while phyllosticta is more random across the leaf and the phyllosticta has a very distinct purple edge to the leaf spotting.