Identification
The tomato hornworm is a large, green caterpillar that can grow up to 4 inches long. It has a distinctive horn-like projection on its rear end and diagonal white stripes along its body. The adult form, the five-spotted hawk moth, has a wingspan of about 4-5 inches and is grayish-brown with light spots on its abdomen. These pests are commonly found in North America, particularly in regions where tomatoes and related crops are grown.
Lifecycle & Reproduction
Tomato hornworms undergo complete metamorphosis. Females lay eggs singly on the underside of leaves, and the eggs hatch within 5-7 days. The larvae feed voraciously for 3-4 weeks before burrowing into the soil to pupate. The pupal stage lasts 2-4 weeks in summer but can overwinter in colder climates. Multiple generations can occur annually in warm regions.
Habits, Diet & Behavior
Tomato hornworms are primarily active at night, feeding on leaves, stems, and fruit of tomato plants, as well as other members of the Solanaceae family, such as peppers, potatoes, and eggplants. They blend in well with foliage due to their green coloration and can defoliate plants rapidly if left unchecked. The adult moths feed on nectar from flowers.
Where You’ll Find Them / Typical Locations
These pests are commonly found in home gardens, greenhouses, and agricultural fields where tomatoes and other solanaceous plants grow. They hide on the undersides of leaves and along plant stems during the day, making them difficult to spot.
Threats & Danger
Tomato hornworms are highly destructive to tomato plants, causing significant defoliation and fruit damage. Their feeding can weaken plants and reduce yields. While they do not pose direct harm to humans or animals, their large size and rapid feeding can devastate crops in a short period.
Prevention
- Inspect plants regularly for signs of damage and remove larvae by hand.
- Encourage natural predators like parasitic wasps, ladybugs, and birds.
- Rotate crops annually to disrupt their lifecycle.
- Use floating row covers to prevent egg-laying by moths.
- Maintain healthy soil with organic matter to support beneficial insects.
Signs of Infestation
- Large, irregular holes in leaves and stems.
- Green droppings (frass) on leaves and soil.
- Wilted or stripped foliage on tomato plants.
- Presence of large green caterpillars with white markings.
- Increased sightings of five-spotted hawk moths around dusk.
How to Get Rid of It
- Handpick and remove hornworms from plants.
- Apply Bacillus thuringiensis (Bt) to target larvae.
- Introduce beneficial insects such as braconid wasps.
- Use neem oil or insecticidal soaps to deter feeding.
- For severe infestations, apply targeted insecticides labeled for hornworm control.