Crapemyrtle Bark Scale are insects, not a disease, so if any pesticide is warranted to manage them, it would require use of one or more insecticides, not a fungicide. (Most plant diseases cannot be cured, but if caught early, new infections from the disease spores can be suppressed.)

The page linked above provides life cycle information that is currently known for this pest (which is fairly new to the Maryland area and still being studied). That page also links to a general scale information page which includes management options, ranging from physical removal (not as practical for extensive infestations or large trees) to insecticide.

For some insecticide ingredients, Maryland law requires that they be applied by a certified pesticide applicator, a license that many landscapers and arborists will hold. Even for chemicals not requiring hired help to apply, it's recommended to have a professional applicator use them anyway, because they will have better-calibrated equipment and the personal protective equipment (PPE) needed to be spraying a tree over their heads, if that is the type of treatment used. (For injectable pesticides, they will have equipment that gardeners can't get at local garden centers.)

For extensive scale populations, good suppression might take at least a year of intervention, even if pesticides are used. Fortunately, several native insects eat scale, and low populations of scale can exist on a plant with little harm, and we don't want scale treatment chemicals to harm them so they can continue to suppress scale for the long term. Experienced and well-trained pesticide applicators (such as those who practice IPM, integrated pest management that prioritizes non-chemical treatment methods where possible) will be able to not only monitor the scale to determine what part of the life cycle it's in, but can look for these beneficial scale predators as well. (One of the ladybug species that eats this scale, for example, has larvae that look almost identical to the scale themselves.)

Miri