Yes, chemicals in the neonicotinoid group of insecticides (which includes imidacloprid and dinotefuran) are regulated in Maryland, such that it is illegal for the general public to purchase and apply them outdoors (a few formulations for houseplant pests exist and are permitted). Certified pesticide applicators are allowed to apply them, and these individuals are certified by the Maryland Department of Agriculture. Many landscapers and arborists hold this certification. A primary reason for the regulation enacted several years ago was to protect pollinators, since systemic ingredients such as these might be transported into a plant's nectar and pollen, exposing bees and other organisms to the insecticide. The page linked above goes into more detail.

Managing a high population of scale insects can be difficult, and successful suppression might take at least a year to achieve. One option is the use of systemic insecticides, but other insecticides might work well enough if used at the right time and applied thoroughly, which still may involve hiring a certified pesticide applicator (as they will have the training to know when to use each ingredient, how to use them properly, and will have higher-grade equipment to apply them more effectively, especially for larger trees). Information about the life cycle of this particular scale, the details of which are still being studied since it's fairly new to Maryland, and information about scale management options in general can be found on these pages:

• Crapemyrtle Bark Scale in Home Gardens
• Introduction to Scale Insects (see the "management" section near the end of the page)

Miri