(European Hornbeam) tree was treated with Cleary’s 3336 granules early this spring. I live in Charlotte NC 7b
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Not 100% certain but I would say Sooty mold, which is a dark colored fungus that grows on honeydew excreted by piercing sucking insects or on substances exuded from leaves of certain plants. So the root cause is an insect that leads to a fungal issue, try treating the insect. Common insect pests would be (aphids, scales, mealybugs, psyllids)…again I am not 100% certain but that’s the direction I would go.
I originally thought it was Sooty mold too but it doesn’t wipe off (from my understanding Sooty mold wipes off). Thanks for your help.
I have a half dozen Korean hornbeams that struggle in my South Carolina climate. I frequently see some form of black spot on the leaves. Might be what you’re seeing on yours? Definitely not positive, but looks like it could be one of the strains of black spot. I’ve treated it with simple baking soda spray, which knocked it down, but it comes back eventually. I’ve also used systemic and topical chemicals. I do know that you have to remove infected leaves and destroy them to prevent spreading it. Many species are susceptible to black spot.
Good luck -good news it’s not fatal to your tree, just unsightly!