How do I treat the black spots and fungus on my large trees?

Asked August 14, 2014, 7:48 PM EDT

I am asking for advice on treating large trees in my yard that seem to be in trouble this summer. I have an oak tree that has suffered from nutrient deficiency and fungus for several years, but the problem appears much more severe this year. I also have two very large silver maples that have black spots on the leaves. This is the first year that we've had this problem. I am attaching photos of the tree leaves.

Since we now have multiple trees on our property that are not healthy, I am worried that there is something wrong with our soil. I am hoping someone can help me identify the source of the problem and give us some suggestions in treating the trees that will not break the bank.

Hancock County Indiana

1 Response

Beginning with your oak, it is suffering from an iron deficiency. Utah State Extension has a great publication explaining what should be done to help treat/prevent this in future oaks: Preventing and Treating Iron Chlorosis in Trees and Shrubs. Purdue also has some great publications on this that can be found here: The Leaves on My Trees Are Turning Yellow.

On your maple leaves, this is called tar spot. It is just a natural fungus that occurs when the conditions are right. It is not a detriment to the tree at all. For more information, you can visit Tar Spot of Maple.