Caterpillars and worms will feed on plants, chewing holes in leaves and stems. Larvae that develop into butterflies are a nuisance, but since butterflies themselves generally don’t damage plants, they can be left alone or picked off if necessary. Caterpillars can be controlled in several different ways. Natural predators such as birds might help; install a birdbath to draw winged visitors to the garden. Discourage moths from laying eggs by using floating row covers over plants, but make sure to remove row covers when food plants need to be pollinated. Biological material Bt (Bacillus thuringiensis) is a garden pest control method that is harmless to people, animals, and beneficial insects.