Why does my crape myrtle have white on the leaves?
Why Does My Crape Myrtle Have White on the Leaves
Certified GKH Gardening Expert
It sounds like you have powdery mildew. This article will help:
Neem oil can help with this fungus as well. Here is more info: https://www.gardeningknowhow.com/plant-problems/pests/pesticides/neem-oil-uses.htm