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Hosts: Primarily tomato but can also attack eggplant, pepper, and potato.
Description: The larval stage of this insect is a 3 1/2 to 4 inch long pale green caterpillar with white and black markings. There is also a brown form but it is not as common. One of the last abdominal segments has a spine-like red or black horn that that gives this insect its name. The adult is the Sphinx moth; a grayish-colored insect with a wing spread of 4 to 5 inches.
The larva is the damaging stage and feeds on the leaves and stems of the tomato plant and leaving behind dark green or black droppings.
Recommendations: This insect is parasitized by a number of insects. One of the most common is a small braconid wasp. Larva that hatch from wasp eggs laid on the hornworm feed on the inside of the hornworm until the wasp is ready to pupate. The cocoons appear as white projections protruding from the hornworm's body. If such projections are seen, leave the hornworms in the garden. The wasps will kill the hornworms when they emerge from the cocoons and will seek out other hornworms to parasitise.
Handpicking is an effective control in small gardens. Bt - Bacillus thuringiensis - and other insecticides may also be used to control hornworms.
1. Tomato Hornworm, Cornell University Extension Service
2. Ortho Problem Solver, Ortho Information Service