Tomato hornworms (Manduca quinquemaculata) can be a serious pest in gardens, causing significant damage to tomato, pepper, and eggplant plants. 

Host Plants

The tomato hornworm is a common pest of tomato, pepper, and eggplant plants. These plants are the preferred host plants of the tomato hornworm and are where the caterpillar will lay its eggs and feed as it grows.

However, the tomato hornworm is not limited to these plants, and it is also known to feed on other plants in the Solanaceae family, such as potato, tobacco, and nightshade.

Regions impacted

The tomato hornworm is found in many regions throughout North America, including the United States, Canada, and Mexico.

Description

The tomato hornworm is a large caterpillar that can grow up to 4 inches (10 cm) in length. It is green and has white stripes running down its back and sides. The most distinctive feature of the tomato hornworm is its large, horn-like protrusion on its rear end.

The caterpillar can blend in with the foliage of its host plants, making it difficult to spot. However, its large size and distinctive markings make it easier to detect once you know what to look for.

Life Cycle

The life cycle of the tomato hornworm typically consists of four stages: egg, larva (caterpillar), pupa, and adult (moth).

1. Egg stage: The female tomato hornworm moth lays her eggs on the leaves of tomato, pepper, and eggplant plants. The eggs are small, round, and green in color, and they hatch within a few days.

2. Larva stage: After hatching, the larvae feed on the leaves and stems of their host plants. The tomato hornworm caterpillar grows rapidly, molting several times as it grows.

3. Pupa stage: When the caterpillar has reached full size, it pupates in a cocoon on the ground or in plant debris. The pupa stage lasts several days to a few weeks, depending on the temperature and other environmental conditions.

4. Adult stage: After pupation, the adult tomato hornworm moth emerges. The moths are gray or brown in color, with a wingspan of up to 5 inches (12 cm). The moths feed on nectar from flowers and mate, and the females lay their eggs on the leaves of tomato, pepper, and eggplant plants, starting the cycle anew.

Damage and Detection

The tomato hornworm can cause significant physical damage to tomato, pepper, and eggplant plants. The caterpillar feeds on the leaves, stems, and fruit of these plants, causing ragged holes in the foliage and consumption of the fruit.

In heavy infestations, the caterpillar can defoliate entire plants, leaving only the stems behind. 

In addition to the direct damage caused by feeding, the tomato hornworm can also spread plant diseases, as the caterpillar feeds on infected plant tissue and then moves to healthy plants, spreading the disease in the process.

Prevention and Control

There are several steps you can take to prevent tomato hornworm infestations on your tomato, pepper, and eggplant plants:

1. Remove plant debris: Regularly remove any dead leaves, stems, or other plant debris from around the base of your plants. This will help to reduce the number of pupae that can survive and emerge as adult moths, starting the cycle anew.

2. Use insect-repelling plants: Planting insect-repelling plants near your tomato, pepper, and eggplant plants can help to keep tomato hornworms away. Some plants known to repel tomato hornworms include borage, calendula, dill, basil, and thyme.

3. Use row covers: Covering your plants with row covers can help to prevent adult moths from laying their eggs on the plants. Be sure to remove the row covers during flowering so pollinators can access the plants.

4. Hand-pick the caterpillars: Check your plants regularly for the presence of tomato hornworms, and hand-pick the caterpillars and dispose of them.

5. Use biological controls: Certain species of parasitic wasps, ladybugs, lacewings, and birds feed on tomato hornworms, and they can help to control populations of these pests. Encouraging these beneficial insects and animals in your garden can help to reduce the impact of tomato hornworms.

6. Use insecticides: If necessary, use insecticides to control tomato hornworm populations. Be sure to follow the manufacturer's instructions and to use the insecticide only as directed.

If you have questions or concerns about preventing tomato hornworms on your plants, it is best to consult with a local horticulturist or agricultural extension office for specific recommendations for your area. They can provide guidance on effective preventive measures and can help you determine the best course of action for your specific situation.