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