Fact Sheet FS1389
Figure 1: Hornworm caterpillar eating a tomato plant in a garden.
Introduction
Hornworms are garden pests of tomatoes and tobacco, and less commonly, other plants in the nightshade family (Solanaceae), which include peppers, potatoes, and eggplants. They also have been known to feed on weeds such as horse nettle and jimsonweed. These insects feed rapidly and can defoliate tomatoes in just a few days, often to the surprise of gardeners because they blend so well with the host plant. Hornworms are the caterpillar stage of large moths and get their name from their worm-like appearance and the distinct, protruding "horn" on their posterior end. They will later develop into hawk moths, which feed on nectar from flowers and do not damage garden plants. Two species of hornworms, Manduca quinquemaculata, the tomato hornworm, and Manduca sexta, the tobacco hornworm, may be found in New Jersey gardens during the summer and early fall.
General Biology
Hornworms are large green caterpillars, reaching 3 to 4 inches long, roughly the size of a human pinky. While these species are nearly identical in appearance as well as the damage they cause, there are minor physical differences between them. Tobacco hornworms have 7 white stripes, and their horn, located on the rear, is typically red. Tomato hornworms have 8 V-shaped white lines that run diagonally to the body, and a dark green or black horn. A clever way to remember how to identify the tomato hornworm is V8: there are 8 Vs on its body, and V8 is a brand of tomato juice.
Figure 2: Close up of a tobacco hornworm on a plant stem.
The hornworm life cycle begins when a female moth lays an egg, which hatches into a larva (caterpillar), develops into a pupa, and finally emerges as an adult hawk moth. Eggs are roughly 1/16th of an inch in size, light green or white in color, laid singly, and are predominantly deposited by the moth on the undersides of the foliage, and less commonly, on the upper leaf surface. The egg stage lasts an average of 5 days. After the eggs hatch, the hornworm larvae will immediately begin feeding on the leaf they were laid on.
Caterpillars grow in steps where they shed their skin multiple times; each of these stages between molts is called an instar. There are typically 5 total instars during the larval development; the total time it takes for larvae to develop is around 20 days. Once larvae have matured, they will drop and burrow 4 to 6 inches into the soil. The pupae will then develop inside a protective chamber known as a pupal cell. Pupae are dark brown in color and tend to be about 2 to 3 inches in length.
Figure 3: Adult hawk moth.
Once the pupae undergo metamorphosis, tobacco hornworms will develop into Carolina sphinx moths and tomato hornworm will become five-spotted hawk moths. These species are difficult to distinguish due to their similar appearance and may often be misidentified. For these reasons, they are discussed collectively here. Adult hawk moths are large, dull gray to grayish brown and with wingspans up to 5 inches. Bright orange spots line the sides of the abdomen, which contrast vividly with the black coloration around them. In flight, they may resemble hummingbirds because of the way they hover above flowers when feeding. The entire life cycle can take around 30 to 50 days to complete and may vary with temperature.
Evidence in the Garden
Hornworms have chewing mouthparts and typically feed on upper foliage first before moving downward to lower leaves. They will also feed on blossoms, stems, and unripe fruits. A bare stem is a sign a hornworm may have fed on the plant. Most damage occurs during the final instar, when their large size enables the hornworm to strip foliage rapidly. As a result, their presence often goes unnoticed until the host plant has already sustained significant damage. Damage to the fruit of the host plants can leave large wounds, which make the fruit vulnerable to opportunistic pathogens.
Figure 4: Hornworm causing damage to a tomato.
Another way to identify that a hornworm has been in the garden is by their droppings. The larvae will leave behind frass pellets, which is their fecal matter, on the ground and the foliage. These appear dark green-black and may look like small stars or flowers. If the frass pellets are darker, they may be older, which could mean that the hornworm has since travelled. More photos of evidence, as well as photos of the frass pellets are linked below in Related Resources.
Management
Tomatoes and other nightshades in the garden should be frequently monitored during the summer for hornworms. Since the caterpillars are most active at dusk or dawn, it is recommended to use a flashlight at night to locate them. They may be difficult to find due to their ability to blend in with the plant, especially if they are younger and smaller caterpillars, so pay special attention when searching. They may also be found on the underside of leaves. Shaking the plant over cardboard or paper is a useful method to remove larvae. Caterpillars can also be plucked off the foliage by hand and killed by cutting them in half or placing them in soapy water. However, if the hornworm is currently being parasitized by braconid wasps, it should be left alone to remain on the plant (see more information below). Additionally, tilling the soil after harvest is recommended as it will kill 90% of the burrowing larvae. Tilling can also be useful in the spring to disrupt and kill overwintering pupae as it will expose them to the elements. Weeds in the nightshade family may harbor hornworms, so managing these plants early on is recommended.
Figure 5: Cocoons of a braconid wasp on a parasitized hornworm.
For biological control, there are many insects that predate on hornworms. Lady beetles, green lacewings, minute pirate bugs, spined soldier bugs, and paper wasps prey on younger stages like eggs and early instars. Plants that attract these bugs can be planted in the garden to manage hornworms. Paper wasps paralyze hornworms and carry them to their nests, where the caterpillar will serve as a food source for the developing larvae. Birds and other small vertebrates may also feed on hornworms. Additionally, there are many parasitoid species of wasps that may target hornworms, such as Trichogramma spp. and braconids. Braconid wasps lay eggs inside the body of the hornworm caterpillar. When the eggs hatch as larvae, they will feed on caterpillar from the inside. Once the larvae mature, they will emerge from the caterpillar, attach to the outside of its body and form white cocoons (Figure 5), where they will pupate. This process kills the hornworm. If a hornworm is spotted in the garden with these white cocoons, do not kill them, as new braconid wasps will emerge to parasitize and kill other hornworm pests, continuing the life cycle.
Insecticides, while not usually recommended for small home gardens, can be applied on larger fields. It may be necessary to apply if there are more than one larva per 10 plants. Bacillus thuringiensis (Bt) is a bacterium that naturally occurs in soil and acts as an insecticide. This bacterium directly affects the digestive system of the caterpillar, preventing them from eating, and causing death. Bt is safe for pollinating insects, animals, humans, and the environment as it is only poisonous to caterpillars. However, it is most effective on younger larvae, as a smaller amount is required to achieve control. When using any insecticide, read and carefully follow all label directions for usage, storage, and disposal.
To get help with an insect or other horticulture issue you are facing in your garden or landscape, submit a request for support at Go.Rutgers.edu/GardenHelpline.
This fact sheet is based on the original work of Gerald M. Ghidiu, Extension Specialist Emeritus in Vegetable Entomology, Retired.
Related Resources
Please see FS1123, Vegetable Insect Control Recommendations for Home Gardens, for more information.
References
February 2026
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