I do not recommend spraying your basil plants with an insecticide. Not only are the leaves rather sensitive but they also the edible part of the plant. It could be earwigs or flea beetles. Try to identify the culprit by using a flashlight at night or by setting a trap. Wad up a bit of damp newspaper and lay it near the basil plants. After a few days check the folds of the paper for earwigs, sow bugs or tiny black flea beetles and dispose of the guilty basil chompers. You can remove the lowest most damaged leaves, give your basil plenty of sun and I think you'll have plenty of pesto to enjoy all summer long. Keep growing, Marianne Binetti