Hello, I have a river birch which I planted three years ago. It's been growing well, but this year it has been infected with something that resembles white mold. Every year it has been infested with aphids, but I have found that it can grow new foliage faster than the aphids can damage it. When I saw some leaves shriveling earlier this spring, I just assumed it was the aphids. But upon closer examination, I founds that the tops of the leaves are pretty much all covered with some white powdery substance, and the bottom of the wrinkled leaves are completely packed with some type of white substance. I'm wondering if you can tell me what I am dealing with, and what treatment, if any, you would recommend. Whatever is going on, it seems much more severe than the usual aphid infestation. I have attached a few pictures, which hopefully demonstrate the problem. Thank you for your help. Best, James