Caterpillars on Tomatoes

It sounds like you're seeing tomato hornworms, which can grow to an alarming size! Like most caterpillars, hornworms can be controlled by using Bt, Bacillis thuringiensis.However, since tomato hornworms can do a lot of damage in a short time, you may want to remove the ones you see by hand. Note: If you see a caterpillar with what looks like grains of rice all over it, relocate it elsewhere in the garden rather than killing it. It has been parasitized by a certain wasp laying its eggs on it. These small wasps are harmless to humans, but will help the hornworm population in check. (The parasitized hornworm will die anyway.)