You can use the fungicide of your choice.

If you want to go the organic route, try a neem oil or baking powder spray. If you want to go the synthetic chemical route, both Immunex and Immunox (both made by Spectracide) have been found to be especially effective for PM on Crape Myrtles.

Further info on powdery mildew on Crape Myrtle is available at the Crape Myrtle Trails site linked below.

Dawn

Here is a link that might be useful: Crape Myrtle Trails of McKinney Website

Dawn
That's strange, I'm seeing PM on just about everything in the veggie garden, but non on the zinnias or Crepe Myrtle.
I've tried several things, (including Neem Oil). If none of my efforts work, I may go Baking Powder next. The juries still out on the trial of dilute bleach solution. I KNOW it's worked for me before on zinnias and morning glories.

Barbara

Oops...I meant Baking SODA. Better correct that quickly.

I'll find a PM page and link it. The one I'm thinking of mentions corn meal juice. It is anecdotally reported to work on all kinds of fungal issues, but I haven't tried it myself.

I'm not seeing any PM. Oh, wait, that's right....we are too hot and too dry here. I'd almost welcome PM on my zinnias if it meant we'd get some rain.

Dawn

Here is a link that might be useful: Dirt Doctor Discusses PM