We have found several large green caterpillars on our tomato plants and want to know how to stop them. They are bright green, no stripes, about 4 inches long, bright green and have small horns at the head.
Those are tomato hornworms. This article should be helpful:
If you have children, you can catch a couple of these worms, keep them in a jar with an air source and feed them some of your tomato stalks. They turn into Hummingbird Moths over time. Kids seem to find this fascinating and the moths are beautiful.