hornworm

Hornworm refers to the larval stage of several species of hawk moths (family Sphingidae), most commonly the tobacco hornworm (Manduca sexta) and the tomato hornworm (Manduca quinquemaculata) in North America. These large caterpillars are named for the horn-like tail projection at their rear.

Description and biology

Hornworms are typically green, but can vary in color from brown to gray and may display lighter markings. They grow to several centimeters in length and possess a characteristic tail horn, which is usually black or brown. They feed voraciously as caterpillars and later pupate in the soil, from which a hawk moth emerges. Adults are robust, night-flying moths with a long proboscis used to visit flowers for nectar.

Host plants and distribution

Hornworms primarily feed on plants in the nightshade family, including tomato, tobacco, pepper, and potato. They are common garden pests and occur in various regions where their host plants are grown. While the two species most often discussed in North America are Manduca sexta and Manduca quinquemaculata, related hornworms occur on diverse hosts in other parts of the world.

Impact and management

Hornworm feeding can cause significant defoliation and fruit damage, particularly in tomato crops and greenhouse settings. Detection is aided by nighttime feeding patterns and the presence of frass on leaves. Management options include manual removal of caterpillars, encouraging natural enemies such as parasitoid wasps (for example, Cotesia congregata), and the use of biological insecticides such as Bacillus thuringiensis kurstaki or spinosad. Sanitation (removing pupal sites) can help reduce reinfestation.