Q.Crepes Have White Mold-Looking Spots
Our crepes have white mold-looking spots on the branches and the branches are black. The leaves look healthy and the trees are budding.
It does sound like Sooty Mold.
This can be caused by Aphids.
I recommend a treatment with Neem Oil.
Here are links with more information.
https://www.gardeningknowhow.com/ornamental/trees/crepe-myrtle/crepe-myrtle-tree-problems.htm
https://www.gardeningknowhow.com/plant-problems/disease/how-to-get-rid-of-sooty-mold.htm
https://www.gardeningknowhow.com/plant-problems/pests/pesticides/neem-oil-uses.htm