Tomato Hornworm

The host plant is primarily tomato but tomato hornworm can also attack eggplant, pepper, and potato. The hornworm feeds on the leaves and new stems of the tomato plant, causing extensive damage. During July and August they also occasionally feed on the fruit.

The larval stage of this insect is a 3½- to 4-inch long, pale green caterpillar with white and black markings and a projection or spike on the last segment, hence the name"hornworm." The adult moth, called a sphinx or hawk moth, is a medium to large, heavy-bodied moth that is a mottled gray-brown color with yellow spots on the sides of the abdomen and a wing spread of 4 to 5 inches.

The adult moth lays eggs on the undersides of tomato leaves in late spring. The eggs hatch in six to eight days. The fully grown larvae then burrow into the soil to pupate. The pupa may remain in the soil all winter and emerge as a moth the following spring, or,if the weather conditions are suitable, the moth may emerge from the pupa in two to four weeks. The moths emerge from the soil, mate, and then begin to deposit the eggs of the next generation on tomato plants.

Handpicking is an effective control in small gardens. Bacillus thuringiensis (B.t.) and other insecticides may also be used to control hornworms. This insect is parasitized by the larvae of a number of insects, one of the most common being a small braconid wasp.Many wasp larvae feed inside the hornworm, eventually killing the caterpillar.

Adapted from the Cornell Cooperative Extension, 1999