This does look like crepemyrtle bark scale, yes, and it's a relatively new and troubling pest in Maryland. (See link below, which is written for the horticulture industry and not homeowners, but provides information for identification.) We have informed our entomologist who is tracking such infestations, and he may reach out to you via email if he would like more information.

In the meantime, using the systemic product you mention (if it's active ingredient is acephate) will not be effective, as it is not absorbed into the particular plant tissues that the scale are feeding on. Instead, a different chemical would need to be applied by a certified pesticide applicator (likely via an arborist) as they are restricted-use and not available to homeowners. Let them know that either Dinotefuran or Altus is the recommended insecticide for this particular pest. Repeat treatments may be needed, but see what the applicator determines based on the instructions of the individual product used. Let them know you recently applied the Bonide systemic (including what its active ingredient is), as this may impact when the other treatments can be used.

https://extension.umd.edu/resource/crapemyrtle-bark-scale

Miri