Hornworms are the larvae of hawk- or hummingbird-like moths and are commonly found on tomato plants. They are large, green, white-barred worms with a slender horn pointing upward at the rear end.
Adult moths appear in May and June and fly about at night, depositing greenish yellow eggs singly on the lower sides of leaves. The eggs hatch in about one week and the new larvae feed for a few weeks.
Only the larvae feed on tomato plants, but during their development, they can consume large quantities of foliage and may grow up to 3-4 inches long. They are often difficult to find because their color blends in or camouflages with tomato foliage background. Often they remain undetected until considerable feeding has occurred. If left unchecked, they may destroy the plant. In addition to tomatoes, hornworms may also feed on eggplant, potatoes, and peppers.
Non-chemical: Hand-picking the worms in home gardens often provides satisfactory control. Hornworms may be attacked by a parasitic wasp. This wasp places its eggs under the skin of the hornworm. When the wasp larvae hatch, they feed internally and pupate. The pupae appear as small white cocoons on the back of the hornworm. If hornworm larvae are infested with wasp cocoons, the hornworms will stop feeding and their parasitized bodies can serve as a source for increasing the beneficial wasp population.
Chemical: Contact your county Extension office for current pesticide controls.