Hello Gardeners, I’m Amanda McNulty with Clemson Extension and Making It Grow. Some caterpillars that look incredibly frightening are actually harmless! The tomato hornworm which is not only huge up to four inches long (after he eats half a tomato plant in one night) but also has a big horn on its rear end. Fortunately, they are all show and can’t do you any harm if you hand pick them (the best control method). Nature helps control these caterpillars, too by providing braconid wasps who lay their eggs on this juicy piece of meat. The eggs hatch into larva who eat the inside of the caterpillar, and then pupate on its back –looking for all the world like upright grains of rice. If you see a tomato hornworm with these structures leave it be as the tiny, completely harmless to human wasps which emerge, will help control future caterpillars. Plant cilantro to attract the adult wasps to your garden.