Tomato Hornworm – Identification and Control

Last updated May 1, 2023

Tomato Hornworm is one of the most destructive pests of tomato plants. These insects will destroy tomato plants if not controlled properly.

Identification

Tomato Hornworm

Tomato hornworms are enormous caterpillars that can grow up to 4 inches (10 cm) long, which they will reach after eating leaves from your plants for several weeks.
Most tomato hornworms have a horn protruding from the back of their bodies.
Tomato hornworms are green in color, with white diagonal lines running down their sides.
The larvae are usually found on the underside of leaves or on stems.

Five Spotted Hawkmoth

Same as tomato hornworms, the five spotted hawkmoths are very large insects.
They have narrow grayish-brown wings.
The abdomen usually has five, but it can also be six pairs of yellow spots.
The forewing is a dark brown and gray color.

Lifecycle

Tomato hornworm will spend winter as a pupa and emerge as an adult Five Spotted Hawkmoth in mid-spring. After mating, females will lay oval, light green eggs on the leaf surface.

Caterpillars will hatch and feed on the host plant’s leaves and stems. These insects will go through 5 instar stages before dropping down to the soil, burrowing themselves, and transforming into a pupa. Moths develop in a couple of weeks and start the second generation.

The caterpillars of the second generation will feed, drop, and burrow themselves in the soil. The difference from the first generation is that the caterpillars will pupate throughout the winter. Adult moths will emerge in the next growing season. [1]

Damage They Cause

Tomato hornworms eat voraciously, stripping leaves off plants and even devouring entire stems. Due to their green color, tomato hornworms are less noticeable while feeding.

As they become bigger, the amount that they eat increases. So is the damage. These large-sized hornworms can destroy not just leaves and stems but fruits also.

Plants They Attack

As the name indicates, these caterpillars mainly feed on tomato plants. However, they are also known to feed on tobacco, peppers, potatoes, and other plants belonging to the solanaceous family.

As an alternative food source, they are able to eat some of the weeds like jimsonweed and horsenettle.

Live Biological Control

Attract predatory insects to your garden, such as assassin bugs and braconid wasps.

Also, attract ladybugs, lacewings, and paper wasps. They will feed on eggs and young caterpillars.

Organic Control

Organic products that contain spinosad will control the tomato hornworm population. There are not many other organic products that can prevent or destroy these pests.

Preventive actions

Pick off the tomato hornworms with your hands. Dispose of them in soapy water. Physical removal usually is enough to control these pests.
Plant marigold, dill, and basil near tomato plants to deter tomato hornworms.
Remove part of the plant with hornworm on it (do this only if you do not want to touch the caterpillar).
Attract birds to your garden, and they will pick out the juicy tomato hornworms for you.
Tilling the soil is also effective in killing the overwintering larvae.

More About Tomato Hornworm

If you see a hornworm with white cocoons attached to its back (picture below), do not remove it. These are cocoons of a beneficial parasitic wasp (braconid wasp). They will hatch and feed on the hornworm from the inside. The wasps will pupate inside the hornworm, and adults will hatch, killing the host and further controlling the hornworm population.