I have a poplar tree (aka tulip tree) in my property that has developed some kind of disease in the last couple of years. The tree starts the season looking great. New leaves look great in the spring but right around this time (May-June) they start getting black spots that grow in size and then the leaves drop off. I'm sure is some kind of fungal disease since it coincides with the rainy season here, but nothing else seems to be affected with it. The pictures show a new leaf, an older fallen leaf, a branch view, and the whole tree. I'm in North Central Florida. Any help from the pros with identification/treatment is appreciated. Thanks.