Knowledgebase
Apple tree leaf spots #868330
Asked May 14, 2024, 6:12 AM EDT
Washtenaw County Michigan
Expert Response
Hi Jenny,
The brown and black colored spots on the leaves are caused by a disease called apple scab. This is a disease caused by a fungus. I don't know if you are able to purchase a fungicide from a home and garden store to try to manage this disease.
Here are some links to MSU Extension articles about apple scab:
https://www.canr.msu.edu/ipm/diseases/apple_scab
https://www.canr.msu.edu/resources/apple_scab
Unfortunately, this disease is very difficult to manage. One thing you can do in the fall, is rake up all of the leaves from under the tree and burn or compost them. The fungus overwinters in the leaves and will infect your tree next year if those are not removed.
The raised orange-colored lesions on the leaves are caused by an insect. These will not cause any major problems.
Pruning is best done after leaves drop in the late fall or in the spring before the tree leafs out.
Best regards,
George Sundin