The tops of my crape myrtle branches are covered with a thick white mold. It appears as though they have been coated with a thin layer of soft cotton. The mold covers about 8 to 15 inches on each branch. Lower branches do not seem to have the problem as yet. I have cut back some of the branches that I can reach but think that removing the affected branches would reduce the height of the 3 trees by at least 1/4th. Can you give me some much needed advice? Would this respond to some sort of spray? Should I engage a professsional person to save these beautiful trees?
This is powdery mildew, a fungal disease which is very common on crape myrtle.
Here's what you need to know about managing it: https://extension.umd.edu/hgic/topics/powdery-mildew-trees-and-shrubs
If these are relatively new plants, we'd recommend replacing with varieties that are mildew resistant.
If you have not had a problem in the past, they may be fairly disease resistant and managing with pruning and spraying would be a reasonable investment. You can do this yourself.
You do not want to remove a 1/4 of the shrub this time of year, but you could remove the most infected parts (which are the tallest parts as we understand.)