Google crape myrtle scale and sooty mold and compare to your tree.

In the spring, before it leafs out, spray with dormant oil. I had the exact same thing….black sooty junk all over the tree and then the leaves would drop. The dormant oil completely solved the problem.

It is hard to combat on certain CMs, as some varieties are just more prone to get it no matter what. I have one that gets scale and mildew every year — one thing that helps besides spraying, is thinning it out. I just take out small interior limbs so that it gets more air circulation. And other than rain, I never let the leaves get wet later in the day/night.

Is yours getting good air circulation? Do you know the variety?

Mine gets excellent circulation but it's a good idea to thin some of the interior branches. I will try the dormant oil before I remove it. The owner of a local nursery said it's better to stick with the old established varieties than one of the new ones.

prevention is the key ... once its on the leaves.. there is little you can do .. even if you kill the PM.. to make the leaves 'clean' again ...

so. without pix.. one might ask.. are you sure you didnt already kill it.. or knock it back significantly???

ken

Silvey, does your plant have black sooty mold or powdery mildew? Both can be problematic on susceptible Crape myrtles.