Braconid wasps for tobacco hornworm
Cotesia congregata parasitises tobacco hornworm as well as tomato hornworm. In a field study on tobacco in Kentucky (Jacobsen 2021) it killed 31–57% of tobacco hornworm larvae. NC State says the wasps lay in first- to third-instar hornworms and emerge from the fourth or fifth to pupate in white cocoons on its back. A hornworm carrying them stops feeding and dies, and killing it destroys the next generation of wasps. Pick off only the clean ones.
Before you act
Small parasitic wasps (the common Cotesia species are only 2–3 mm long) whose larvae develop inside a caterpillar or an aphid and kill it. The white, rice-grain cocoons standing up on the back of a hornworm are theirs, and a hornworm carrying them should be left on the plant. How to recognise it, what it is confused with and how to keep it around are on the full Braconid wasps profile.
Other controls for tobacco hornworm
- Bacillus thuringiensis kurstakiMicrobial insecticide · Label rate — DiPel DF lists tobacco hornworm (0.5–1.0 lb per acre on tobacco); the Thuricide home label names only tomato hornworm, at 1–3 tsp per gallon on tomato, pepper and eggplant
- Tachinid fliesWild parasitoid · Wild — keep nectar plants near the crop, no broad-spectrum sprays
- Trichogramma spp.Egg parasitoid wasp · 50k–100k /acre weekly (1–2 /ft² in gardens)
- Paper waspsWild predator (stings) · Wild — tolerate nests away from doors and paths