Jeff,
I believe what you have is a fungi infection of powdery mildew. It is caused by to much moisture and not enough wind/ airflow to dry the plant. To fix this problem you want to allow good airflow over the plant and apply fungicide to the plant. You should be able to pick some up at your local nursery. Follow the instructions on the box when applying the fungicide. When you water the plant just water the root not the leaves. I hope this help. The picture were great. I think you have acted quickly and I think your tree should make!