What Do Tomato Hornworms Eat?
These voracious garden pests primarily feed on plants belonging to the Solanaceae family, with a strong preference for tomato plants. Especially young leaves and stems.
Introduction: The Insatiable Appetite of the Hornworm
Tomato hornworms, the larvae of the Five-spotted Hawkmoth (Manduca quinquemaculata), are notorious for their destructive feeding habits. These large, green caterpillars can decimate entire tomato plants in a matter of days. Understanding their dietary preferences is crucial for effective pest management. They are not picky eaters within their preferred plant families, which is why recognizing the early signs of infestation is essential for gardeners hoping to salvage their harvest.
Preferred Food Sources: The Solanaceae Family
The tomato hornworm’s diet primarily consists of plants from the Solanaceae (nightshade) family. This family includes many common garden vegetables and weeds. The following plants are common hosts:
- Tomato plants: Their namesake and favorite food. They will devour leaves, stems, and even the fruit.
- Pepper plants: While less preferred than tomatoes, hornworms will readily consume pepper leaves, especially if tomato plants are scarce.
- Eggplant: Another member of the nightshade family that can fall victim to hornworm predation.
- Potato plants: Though typically focusing on foliage, they can occasionally attack potato tubers near the surface.
- Weeds: Certain weeds within the Solanaceae family, like horsenettle and jimsonweed, can also serve as food sources, allowing the hornworm population to persist even without cultivated crops.
The Damage They Cause: Defoliation and Frustration
The sheer size of tomato hornworms, combined with their rapid growth rate, means they can cause significant damage very quickly. A single hornworm can strip a tomato plant bare in a week. This can lead to:
- Reduced yield: Defoliation hinders the plant’s ability to photosynthesize, impacting fruit production.
- Stunted growth: Severely defoliated plants may struggle to recover, resulting in smaller, less robust growth.
- Increased susceptibility to disease: Stressed plants are more vulnerable to diseases and other pests.
- Aesthetic damage: Even if plants survive, extensive feeding damage can make gardens look unsightly.
Recognizing the Signs: Frass and Missing Foliage
Early detection is key to minimizing damage. Look out for these telltale signs:
- Missing leaves and stems: Regularly inspect your tomato plants for leaves that have been partially or entirely eaten.
- Frass (caterpillar droppings): Dark green or black droppings on leaves or the ground beneath the plant is a sure sign of hornworm activity. They are usually about the size of a grain of rice.
- Camouflaged caterpillars: Hornworms blend in remarkably well with tomato foliage. Look closely for large, green caterpillars with white stripes and a characteristic “horn” on their rear end.
- Fruit damage: While less common, hornworms will occasionally feed on tomato fruit, creating large, unsightly holes.
Management Strategies: Protecting Your Garden
Various strategies can be employed to manage tomato hornworm infestations:
- Handpicking: This is the simplest and most effective method, especially for small gardens. Simply remove the hornworms from the plants and dispose of them.
- Biological control: Introducing natural predators, such as parasitic wasps (like the Braconid wasp) or Bacillus thuringiensis (Bt), a naturally occurring bacterium that kills caterpillars, can help control hornworm populations.
- Companion planting: Planting basil, marigolds, or dill near tomato plants can repel hornworms or attract beneficial insects.
- Insecticides: In cases of severe infestations, insecticides may be necessary. Choose options specifically designed for caterpillar control and follow the label instructions carefully.
Frequently Asked Questions
What’s the difference between a tomato hornworm and a tobacco hornworm?
While both are large green caterpillars that feed on Solanaceae plants, the tomato hornworm (Manduca quinquemaculata) has eight V-shaped white markings on its sides and a dark-colored horn, while the tobacco hornworm (Manduca sexta) has seven diagonal white lines and a red horn. Their preferred host plants also differ slightly, with tobacco hornworms preferring tobacco and related plants.
Do tomato hornworms eat anything besides plants in the Solanaceae family?
Generally, no. Tomato hornworms are quite specific in their diet and primarily stick to plants within the Solanaceae family*. They might occasionally sample other plants, but they won’t thrive or complete their life cycle on anything else.
Are tomato hornworms poisonous?
Tomato hornworms themselves are not poisonous to humans or pets. However, they can accumulate toxins from the plants they eat, such as alkaloids found in tomato leaves. This can make them unpalatable to predators.
Can tomato hornworms kill a tomato plant?
Yes, a severe infestation of tomato hornworms can definitely kill a tomato plant. The hornworms’ voracious feeding can strip the plant of its leaves, weakening it and making it susceptible to disease.
What eats tomato hornworms?
Many natural predators feast on tomato hornworms, including birds, wasps, lacewings, and ladybugs. Parasitic wasps are particularly effective, as they lay their eggs inside the hornworm, and the larvae feed on the hornworm from the inside out.
What happens if you leave a tomato hornworm on a plant?
If left unchecked, a tomato hornworm will continue to feed on your tomato plant, causing significant damage. It will eventually pupate and transform into a Five-spotted Hawkmoth, which will then lay more eggs, perpetuating the cycle.
How can I attract natural predators of tomato hornworms to my garden?
You can attract beneficial insects like parasitic wasps and ladybugs by planting flowering plants that provide nectar and pollen. Avoid using broad-spectrum pesticides, as these can kill beneficial insects as well as pests.
What’s the best time of year to look for tomato hornworms?
Tomato hornworms are most active during the warmest months of the growing season, typically from late spring to early fall. The exact timing will vary depending on your geographic location and climate.
Are tomato hornworms harmful to humans?
No, tomato hornworms are not harmful to humans. They don’t bite or sting. They are only a threat to your plants.
Can you eat tomato hornworms?
While technically edible, it is not recommended to eat tomato hornworms. They may contain toxins from the plants they’ve consumed. Moreover, they’re not considered particularly palatable.
Do tomato hornworms only attack outdoor plants?
While primarily an outdoor pest, tomato hornworms can sometimes infest greenhouse or indoor tomato plants if given the opportunity. Maintaining good hygiene and inspecting plants regularly can help prevent infestations.
How long does it take for a tomato hornworm to become a moth?
The life cycle of a tomato hornworm, from egg to moth, typically takes about 30-50 days, depending on environmental conditions. The caterpillar stage, during which they cause the most damage, lasts for several weeks.