Mary-- You could check your Crepe Myrtle for scale. Looks like tiny
grains of white rice on the bark. Scale hit the DFW area 3 or 4 years ago. Do not know if it has gotten as far as you. Imidacloprid active ingredient works on scale. I found it as an ingredient in a Bayer for trees. It is a systemic treatment. There is a certain cycle on the tree when it is most effective. Many blessings to you!