First job is to determine who the enemy is. Flea beetles, slugs, and aphid can all be guilty with different control methods. Try setting out a bit of damp newspaper at the base of the plant and see if you find slugs or earwigs inside the folds of the paper. Worry Free Slug bait will control slugs and snails near food crops. Aphid will be tiny green bugs at the tips of the new growth. Pinch these with your fingers. If you find tiny hopping insects this could be flea beetles, and the safe way to control them is to wait until summer heats up and they decline in population, but then put a fresh mulch of rocks or gravel around the base of the plant to cover the earth where they mate. If your basil is potted a mulch of marbles or wine corks will look great while blocking the soil. Rabbits, rats, or deer can also eat basil. If you send a photo of the damage I may be able to give a better guess to the culprit. Keep growing, Marianne Binetti