Slugs or snails? If you aren't seeing pests in the daytime, go out after dark with a flashlight and look, then you will know which pest you are targeting and what the appropriate product would be. Please don't guess, and spray first, identify later - it's best to know what you are dealing with before buying and applying a product.

Young caterpillars will eat leaves until nothings left. Feeding at night and residing in soil during the day. I have two phlox divariculata just planted that are going down fast.