Egg - Hornworm eggs are smooth, spherical, and about 1.3 mm in diameter. Light green at first, they turn white before hatching.
Larva - Mature tobacco hornworm larvae usually have green bodies with fine white pubescence and seven diagonal stripes on each side; the posterior horn is usually curved and red. Tomato hornworm larvae have 8 V-shared markings on each side; the horn is straight and black. Both species are about 75 to 85 mm long when fully grown.
Pupa - Pupae are brown, hard, spindle-shaped, and about 5 cm long. They have a curved, projecting, pitcher-handle-like tongue case. The tongue case of the tomato hornworm is longer and more curved than the tongue case of the tobacco hornworm.
Host Plants - Hornworms feed primarily on solanaceous plants. These hosts include tobacco, tomato, eggplant, pepper, and some weedy plants. Tobacco and tomato plants are preferred for oviposition.
Damage - Hornworms strip leaves from tomato vines. If a heavy infestation develops, caterpillars also feed on developing fruit. Rather than bore into fruit, they feed superficially leaving large open scars. Fruit damage, however, is much less common than defoliation. Hornworm damage usually begins to occur in midsummer and continues throughout the remainder of the growing season.
Life History - Hornworms overwinter in the soil as pupae. Moths of this overwintering generation begin to emerge in early June and may continue to emerge as late as August. Nocturnal in habit, hornworm moths frequently can be seen hovering over plants at dusk. At night, eggs are deposited on the underside of leaves. Each moth deposits one to 5 eggs per plant visit and may lay up to 2,000 eggs.
Hornworms emerge from the eggs about 4 days later, depending upon temperature. After feeding for 3 weeks, hornworms burrow into the soil and spend 4 days as prepupae. In summer, the pupal period lasts 3 weeks after which a new generation of moths emerges. Heavy egg deposition is common in August and early September. At least two generations occur each year in North Carolina.
For chemical recommendations, consult the current North Carolina Agricultural Chemicals Manual.
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