I have been trying to grow Amur maple seedlings for three years as singles, clumps, and forests. Every year I am haunted by what I would assume as fungus...black edges on leaves which usually ends up eating all the leaves on the tree. Then they start over again and here come the black leaf edges again. I have sprayed at least three times this year starting early but have them again this year. Yes all my maples are in my storage shed in the winters where the humidity is higher, but I have a fan running. I know these things are tough and maybe I should just leave outside in my 5-6 zone and I would not have the problem. The fungus only seems to attack the Amur and not other maples in the same shed. Are Amur's just more susceptical than others. Drives me crazy! Help appreciated.