Tomato Hornworm: How To Prevent & Deal With Them In The Garden

Have you been invaded one or more tomato hornworm? I see them every year. Fat and juicy worms that feast on my tomatoes.

One bite here, another bite there and leaving behind large rat-like scat in their wake (a good sign you have them and can’t see them as they blend in so well with the leaves). I might not feel so bad if they’d eat an entire tomato instead of just taking one bite and moving to the next.

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Vine-ripened tomatoes are a thing of beauty. Many gardeners work hard to make sure that they produce plump and juicy fruits once harvest season kicks in. But sometimes, even if you try to keep your tomato plants happy and healthy, problems can arise.

Today, we’ll be talking about one such “problem” the tomato hornworm, one of the most destructive pests that can bring trouble to an otherwise perfect tomato garden and without warning. Let’s get to it!

What are Tomato Hornworms

Tomato hornworms are the larvae or caterpillar of the five-spotted hawk moth. They are common throughout North America.

They are one of the largest caterpillars you’ll see in vegetable gardens growing up to 4 inches long. They appear to be green and with seven diagonal white stripes along their back. They also have a black or red horn projecting from their rear part – thus the name Hornworm.

Their protective coloring lets them camouflage well so it might be difficult to spot them in your garden. Often, you’ll find large areas that have feeding marks on them before you can actually see these caterpillars. Then all of the sudden you see this giant pain in the rear happily feasting on your plants.

Adult moths often emerge in late spring. After mating, they deposit spherical green eggs on the underside of leaves. Five days later, they will hatch and the larvae will then pass through five or six stages before reaching full growth. They overwinter in the soil and appear as brown pupae.

What Do they Affect and How

Tomato hornworms are known to eat various plants from the family Solanaceae. They commonly feed on tomato, eggplant, pepper, tobacco, moonflowers, and potato.

When they are first born the tiny caterpillars can be found feeding on the young leaves near the stem of host plants. Meanwhile, in the evening, you can find the older (they age fast in size) caterpillars feeding on leaves that are farther away from the main body of the plant.

These pests are known for consuming entire leaves and small stems of their host plants. They sometimes even chew pieces from nearby fruits.

How to Deal with Tomato Hornworms in the Garden

While tomato hornworm can be very destructive, there are a variety of ways you can control them in your garden. Including:

Till The Soil

At the beginning and end of the gardening season, plow your garden to get rid of any overwintering larvae.

Keep Predators Around

Use beneficial insects as a biological control against tomato hornworms.

Wasp larvae can attack and feed on hornworms. Once you see any infected hornworms, you can remove them from your garden so the wasps can do their job while preventing any further damage from the hornworms themselves. 

Other beneficial insects can also help get rid of young hornworms or hornworm eggs such as ladybugs and green lacewings.

Plant Companion Crops

Interplanting herbs like dill or basil and even flowers like marigold can help keep tomato hornworms from destroying your tomatoes.

The chemicals found in these plants repel hornworms and can even help improve the flavor of tomato fruits.

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Apply Diatomaceous Earth

This organic substance works by absorbing the oils and fats from insects’ exoskeleton. Its abrasive texture also makes tiny lacerations on the bodies of insects like tomato hornworms which leads to their death.

Spot Treat

If you find that the pest levels in your tomato garden are on the extreme side, you may consider using a fast-acting organic pesticide. Apply to the undersides of leaves where these insects tend to hide.

The first time you see evidence that they have been in your garden you’ll remember the signs: bites taken out of tomatoes, leaves eaten in a big way, and rat-like droppings on leaves and surrounding areas.

You will then know to look for at least one of these caterpillars. Youc an easily remove them by hand as they don’t sting and they aren’t slimy or gross they are just HUGE.