However, if you spot hornworms with white projections protruding from their bodies, leave them alone. These white cocoons are the sign of a small braconid wasp, a natural parasite of the hornworm. The wasps will make short work of their host when they emerge from the cocoons and will seek out other hornworms to parasitize. Keep a close eye on your tomato plants from early July through August, examining the plants daily to check for eggs and small caterpillars. Catching infestations early will make controls more effective.
Prevention also is an important element in hornworm control.
Several insecticides also are used to eliminate hornworms although these are seldom necessary in the home garden. Always choose the safest product for the job and read the manufacturer's label carefully. Be sure to wear protective clothing whenever applying the treatment and dispose of the insecticide as directed. This page is hosted by Communication and Technology Resources , University of Vermont, and maintained by Cathy Yandow . University of Vermont Extension, Burlington, Vermont.