I like to plant Kentucky Wonder pole beans but every year, right after they come up and start getting leaves, something nibbles holes in the leaves until the little plant dies. I've never caught anything on the leaves, top or bottom, so I have no idea what's doing this. The only thing I've found that will keep the nibblers at bay and let the plants live until they have a few more leaves (at which time they seem to be left alone) is dusting them with diatomacious earth. But this has to be done every few days, especially after a rain. Does anyone know what might be eating my plants and what else might be effective at stopping it?