Without a photo of the symptoms, it's hard to determine if that was a correct diagnosis. Generally, there is no bark infection or disease on crapemyrtles, and what people see is instead either lichen (harmless, though uncommon on crapemyrtle due to the smooth and flaking bark characteristics) or a population of an insect called Crapemyrtle Bark Scale. This species of scale has become widespread in Maryland over the course of just a few years since it was first detected; prior to this population expansion, it was only present well to our south.

If scale is present, then management revolves around either manually removing most of the scale (such as with a non-abrasive scrubber, like an old toothbrush or kitchen brush) and/or using an insecticide to treat them. Look for beneficial scale predatory insects, as noted in the page linked above, before deciding to act, since they can help control scale populations naturally. Over the short term, if predators don't seem to be present and if the scale is abundant, then treatment with dormant oil once we're further into late fall or early winter may be helpful. The management section on our Introduction to Scale Insects page, and the horticultural oil page, provide more information, including about when and how a more intensive insecticide treatment may be needed, at which point it might be necessary to hire a certified pesticide applicator.

Miri

You're welcome!