Maple leaf affliction

Asked August 2, 2020, 2:25 PM EDT

Hi MSU Extension, could you please tell me what is causing the brown spots on the leaves of this maple tree and, as a bonus, how we can treat it? It is in Glen Arbor, Michigan. I'm a MGV from Franklin County Ohio, but I'm a Michigander at heart!

Leelanau County Michigan

1 Response

Hello,

There are many foliar diseases that affect maples. Anthracnose and leaf spot are two examples. Anthracnose is a spring disease and usually occurs when there is cool wet spring weather. It is caused by several fungi. Read more about Anthracnose and maple leaf blister here:

https://www.canr.msu.edu/news/why_do_my_maple_leaves_have_spots

The spots may also be tar spot--black spots on the leaves caused by fungi. You can read about it here:

https://www.canr.msu.edu/news/black_polka_dots_on_maple_tar_spot

The leaves look slightly chlorotic, a yellowing between the veins, which indicates a soil nutrient problem—a low level of manganese when the soil is too alkaline.

The fungus responsible is difficult to learn from the picture.

The MSU Plant and Pest Diagnostic Lab may provide a more thorough diagnosis and you would learn whether treatment is necessary and what it would be. Go to: https://www.canr.msu.edu/pestid/ to learn how to submit pictures and samples.

By having the soil analyzed, you can learn the nutrient level of the soil. Obtain a soil testing kit at: https://homesoiltest.msu.edu/

Finally, you could contact a certified arborist for advice. Go to: www.treesaregood.org the website of the International Society of Arboriculture to find an arborist in your area.

Good luck with your maple.

Thank you for contacting Ask an Expert.