A: I can identify a few things here. The black along the bark could be sooty mold from sap-sucking insects. That is what they excrete along bark or on leaves. The damage and stress on those trees seems pretty far along. The heavy presence of lichens are a sign that the tree is in decline. If you cut the trunks down, all the way to the ground, you could leave two or three suckers coming up from the ground, let the strongest one stay in a year or so, and you’ll have a new crape myrtle.

Not worth using any insecticide or treatments at this point.

**UPDATE - Adding feedback here from Walter Reeves, the Georgia Gardener. Perhaps the sap-sucking insects presenting sooty mold are Crape myrtle Bark Scale. They are crusty gray and white bugs visible on the outside of the bark. For control of CMBS, act now using a soil drench containing the insecticide imidacloprid. Follow directions and apply it along the drip line of the crape myrtle.

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