Raising Tomato Hornworm Caterpillar . A hornworm is a common caterpillar found on tomatoes. Prior to joining the dept. EnviroTip 1 Tomato Hornworms Feeling The Love The Resilient Activist from www.theresilientactivist.org I wouldn't think twice about it for most other caterpillars, but since i know tomato foliage is supposed to be at least somewhat poisonous and that's what the. We are leaving the top open or covering it with a screen. Deputy sheriff acted as staff photographer for the dept.