White stuff on crepe myrtle

I'm sure it's some sort of fungus but it seems to be growing on a few of our potted crepe myrtles. Can anybody tell me what it is and suggest a fix for this?

Thanks much!

Can you post a picture of the white stuff?

My guess without seeing it is that it is powdery mildew and a fungicide will take care of that.

Here are several nontoxic fungicide recipes:

https://permies.com/t/93537/nontoxic-Fungicide

I want to emphasize that I live somewhere very different than you do by noting that I have 18" of snow outside right now, so there's plenty of room for me to not know your plants and pests. But it looks like powdery mildew to me too.