What is affecting the leaves on smoke bushes? Is it verticillium wilt?
Question:
I’m trying to determine if my smoke bushes are infected with something or just going into dormancy in an unfamiliar way. 1/4 of the leaves on one of my bushes is affected. I’ve since pruned them off with clean sheers. I think this happened in just a few days. The spots are becoming but not yet brittle. It doesn’t look like verticillium wilt to me, but maybe I caught it early?
Answer:
I’m inclined to think what you’re seeing is leaf scorch, a relatively common occurrence in smoke tree in hot, droughty seasons, often presenting as purplish staining on the foliage. With verticillium, you would be expecting dry, brown, crusty dead spots on the leaf, as well as wilt and collapse of leaves/branches (as pictured here in an Oregon State University resource). Giving the plant a nice, deep watering might help mitigate things.
If you do start to see the spots turning dead and papery brown or if you start getting wilt, we would want to get a diagnostic sample to confirm–unfortunately, the UMaine plant pathologist is on leave for the rest of the year, so we would need to help you get a sample to the UMass diagnostic laboratory, which would involve a fee (we typically provide this service free to residents).
Removal of the affected tissue isn’t a terrible idea, just in case it is early verticillium, but hopefully we’ll get more rain next year and your smoke tree will be back to its usual self.