Description: The larval stage is a 3 ½ to 4-inch long pale, green caterpillar. There are five pairs of prolegs and a horn on the last segment. The tobacco hornworm has seven diagonal white stripes and usually a red horn. The tomato hornworm has Vshaped markings and a blue/black horn. The adult moth has a stout, grayish-colored body with wings that span 4 to 5 inches.
Life Cycle: In the larval stage the hornworm caterpillar passes through four or five stages before reaching full size. This process takes about one month. The caterpillar pupates in the soil giving rise to an adult moth. The adult of the tobacco hornworm is the Carolina sphinx moth. The adult of the tomato hornworm is the five-spotted hawk moth. There are two generations each year.
Damage: Hornworm larva are the damaging stage and are typically found on tomatoes,
but feed on eggplant, peppers and potatoes as well. Caterpillars devour leaves and
stems leaving behind dark green or black droppings.
Control: Hornworms are parasitized by several insects including the small braconid wasp which lays eggs on the larva. When the eggs hatch, the wasp larva feed on the hornworm devouring it from the inside killing the hornworm.
To avoid harming beneficial insects, handpicking hornworms is the recommended control.
Hornworms camouflage themselves among the leaves making it difficult to find them.
Bt (Dipel, Thuricide), Spinosad (Conserv, Captain Jack’s Dead Bug Brew, Monterey
Garden Insect Spray), cyfluthrin (BioAdvanced Vegetable & Garden Insect Spray) are a
few insecticides that can be effective at controlling hornworms. Always follow label
instructions and pay close attention to the harvest interval.
