Cotesia congregata and other Braconidae
Braconid wasps- Kind
- Wild — attract it
- Best for
- Leave cocooned hornworms in place
Pest
Tobacco hornworm
Manduca sexta
The short answer
A large green caterpillar, up to about 4 inches (10 cm) long, with a horn on its tail. It eats whole leaves and small stems of tomato, tobacco and their relatives, and chews into green fruit. It is almost the twin of the tomato hornworm. Tell them apart by two features: the tobacco hornworm has a red horn and seven diagonal stripes, and the tomato hornworm has a black horn and V-shaped marks. Both are managed in the same way. Hand-pick the clean ones and leave any carrying white cocoons, which are already dying and are raising the wasps that control the next generation.
hero macro · larva showing red horn and diagonal stripes
Late-instar Manduca sexta on a tomato stem, showing the red horn and seven diagonal white stripes. Photo: pending.
Identification
The tell is on the side of the caterpillar and on its tail. The tobacco hornworm, Manduca sexta, has seven diagonal white stripes on each side, edged with black, and a red horn. The tomato hornworm, Manduca quinquemaculata, has eight V-shaped or arrow-like marks on each side and a black or bluish-black horn that is less curved. Both are bright green, well camouflaged and up to about 4 inches (10 cm) long when full grown. Both feed on tomato, and Maryland Extension says the tobacco hornworm may be the more commonly encountered of the two.
The adult is a large grey-brown hawk moth called the Carolina sphinx, with a wingspan of up to 5 inches (about 12 cm). NC State notes that tobacco hornworm moths have six orange spots on the abdomen and tomato hornworm moths five. As with the tomato hornworm, the caterpillar is easier to find by its droppings than by sight: look for dark green or black pellets on the leaves and the ground, then search the stems above them.
Easily confused with
- Tomato hornwormAlso a pestEight V-shaped marks (chevrons) on each side and a bluish-black horn, rather than seven diagonal stripes and a red horn. Both eat tomato and are managed the same way.
- Hornworm carrying white cocoonsBeneficial — leave itThe white bodies on its back are not eggs but cocoons of a parasitic Cotesia wasp. The hornworm is already dying: leave it, and the wasps that emerge attack other hornworms.
Damage symptoms
Damage looks the same as the tomato hornworm's. Whole leaves and small stems disappear, often from the top of the plant down, and large pieces are chewed out of green fruit. In North Carolina tobacco, most of the damage comes in July and later, and the heaviest feeding is done by the last one or two instars.
- Whole leaves and small stems eaten, often from the top of the plant
- Bare stems left as stubs where whole leaves have gone
- Large chewed gouges in green fruit
- Dark green or black droppings on leaves and on the ground below
- A caterpillar carrying white rice-like cocoons — parasitised, leave it
Lifecycle & degree days
The pupa overwinters in the soil. Moths emerge in late spring and early summer and lay single eggs on the leaves, and the caterpillars feed for three to four weeks before burrowing down to pupate. Development takes about two months in summer. The number of generations depends on the length of the season: one in Massachusetts, one to two in Maryland, two in most areas (UC IPM) and two to three in North Carolina.
- Larval feeding
- About a month (UMD); 3–4 weeks (UC IPM)
- Instars
- 4–5 (UMD) or 5–6 (NC State)
- Egg to adult
- About 2 months in summer
- Generations / yr
- 1 (Massachusetts) to 2–3 (North Carolina)
- Overwinters
- Pupa in soil, 3–6 in down
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Host crops
Both hornworms feed on plants in the nightshade family. Maryland Extension lists tomato above all, eggplant, pepper and potato less often, and also petunia and calibrachoa in flower beds and baskets. Tobacco is the crop the species is named for.
Monitoring & action thresholds
Action threshold
No numeric threshold for gardens
UC IPM advises treating hornworms only when they cause extensive leaf damage or feed on fruit, and Maryland Extension says hornworm damage rarely warrants an insecticide. The one published number is for tobacco fields (NC State): one or more hornworms over 1 inch long without cocoons per 10 plants, with five cocooned worms counted as one. That figure is not for gardens.
Check tomatoes and their relatives through midsummer. Look for fresh droppings and bare stems at the top of the plant, then search the stems above them, and check leaf undersides for single pale green eggs. Look at the horn and the side stripes to tell which hornworm you have. Before removing one, check its back: a hornworm with white cocoons should stay on the plant.
Beneficial
Biological control
Tobacco hornworm has the same enemies as the tomato hornworm. The best known is Cotesia congregata, a braconid wasp native to the eastern United States. It lays from 50 to several hundred eggs inside a young hornworm, and the larvae emerge to spin the white cocoons seen on its back. In a 2021 field study on a Kentucky tobacco farm, Cotesia killed 31–57% of tobacco hornworm larvae. NC State also lists tachinid flies (Winthemia and Archytas marmoratus), stilt bugs that eat the eggs, and paper wasps that feed caterpillars to their young. UC IPM notes that Trichogramma wasps attack hornworm eggs. Bt works on the caterpillars, best while they are small.
Bacillus thuringiensis kurstaki
Bt (kurstaki)- Rate
- Label rate — ½–4 tsp per gallon on home concentrates; varies by product
- Best for
- Young larvae, when picking is impractical
Tachinidae
Tachinid flies- Kind
- Wild — attract it
- Best for
- Wild larval parasitoids; no release
Trichogramma spp.
Trichogramma wasps- Rate
- 50k–100k /acre weekly (1–2 /ft² in gardens)
- Temp
- 18–29 °C best; weaker at 15 °C
- Best for
- Eggs only — while moths are laying
Cultural controls
In a garden, hand-picking is the main control, and usually the only one needed.
- Hand-pick clean hornworms; a spray of water can make them move and show themselves
- Leave any hornworm carrying white cocoons — the wasps inside are the next generation of control
- Till or dig over the bed after harvest to destroy pupae in the soil
- Check petunias and calibrachoa near the vegetable garden as well
Chemical, last resort
Broad-spectrum sprays kill the wasps and flies that finish off hornworms for you. Never spray carbaryl or spinosad on plants in flower where bees are foraging.Check any product before it goes on. Open the compatibility matrix →
- Bt kurstakiREI 4 h
- SpinosadREI 4 h
- CarbarylREI 12 h
Rating: the effect on this pest's natural enemies if a spray hits them or they feed on treated plants. REI is the re-entry interval on farm and greenhouse labels; home labels usually give none, so follow the label.
Sources
NC State Extension, Tobacco Hornworms (Lopez, 2025)
University of Maryland Extension, Tobacco and Tomato Hornworm on Vegetables
UC IPM Pest Management Guidelines: Tomato — Hornworms (text updated 12/13)
UC IPM Home and Landscape — Hornworms
UC IPM, Relative Toxicities of Insecticides Used in Tomatoes to Natural Enemies (09/16)
UMass Amherst Extension, Tomato Hornworm fact sheet
UF Entomology, Cotesia congregata (beneficial arthropods gallery)
Jacobsen, Ecology and Evolution 11:13884 (2021), Cotesia parasitism of Manduca sexta
DiPel DF label, EPA Reg. 73049-39 (2022)
Page status
Drafted from the sources below, then checked claim by claim against those sources on 23 September 2026.
Suggest a correction →Tobacco hornworm by crop
The same pest behaves differently on different hosts. Each page below gives the host-specific control, rate and threshold.