Ask Mr. Smarty Plants

Stachys coccinea (Scarlet betony) - also Texas Betony, is one of those plants that most references regard as "pest free," or "few problems." Obviously, that is not the case with your plant. We did a little further searching with other members of the Stachys genus and discovered that some of them have problems with slugs, snails and whiteflies. For instance, here is a website on Stachys lanata (Woolly Betony) which is not native to North America but widely grown here. We doubt the pests check plants' passports before they start chewing.

If you scroll down that webpage, you will find a section on Problems - Pests: Slugs and Snails. Another reference mentioned whiteflies. Here is what the website on Wooly Betony had to say about the slugs and snails:

"Slugs and snails favor moist climates and are mollusks, not insects. They can be voracious feeders, eating just about anything that is not woody or highly scented. They may eat holes in leaves, strip entire stems, or completely devour seedlings and tender transplants, leaving behind tell-tale silvery, slimy trails.

Prevention and control: Keep your garden as clean as possible, eliminating hiding places such as leaf debris, over-turned pots, and tarps. Groundcover in shady places and heavy mulches provide protection from the elements and can be favorite hiding places. In the spring, patrol for and destroy eggs (clusters of small translucent spheres) and adults during dusk and dawn. Set out beer traps from late spring through fall."

From University of California Integrated Pest Management: Snails and Slugs.

From the same source: Whiteflies

These both seem to involve a moist environment, so be sure you are not overwatering your Texas Betony and providing a welcoming environment for the pests. According to our webpage on Stachys coccinea (Scarlet betony), the plant likes moist soil and part shade, both good environment for the pests we are discussing.