Answer: There are five fungi that can attack poplar species and all develop during wet weather. To break the disease cycle, be sure to rake up and remove fallen leaves during and at the end of the growing season. There are fungicides which will protect the leaves, but none that will kill the fungus once it has developed. Your best course of action is to wait until the trees begin to leaf out in the spring, then use a fungicide to protect the newly emerging leaves. Not all fungicides work against all diseases so you might want to take a sample of infected leaves to your local Cooperative Extension office for positive identification. Helpful folks there can recommend a fungicide for your trees.
Q&A Library Searching Tips