Extension for Real Life

How to Manage Hornworms on Tomatoes

Have you seen big green worms on your tomato plants? These are likely hornworms – either tobacco hornworms or tomato hornworms. Believe it or not, tobacco hornworms are what you find most often on tomato plants.

As these caterpillars near the end of their larval stage, their appetites increase dramatically, and they can heavily damage your tomato plants. A healthy plant on Monday can be nothing but nubs by Thursday if you don’t notice these worms or their damage soon enough.

So, how do you keep these pests from eating your plants? If you have just a few plants, the best way to get rid of them is to pull them off the plant by hand and dispose of them. Because of their color, they are easily camouflaged. An easy way to spot them is with a black light. Shining this light on the plants will make the worms glow.

Black lights are easy to find and are inexpensive. They come in a variety of forms, including small flashlights.

More About Hornworms

You can tell the difference between the two species of hornworms by their markings and the color of their horn, which is harmless. Tobacco hornworms have seven diagonal white stripes on their side, and their horns are usually reddish in color. Tomato hornworms have eight white V-shaped markings on their sides, and their horns are usually brownish, or “tobacco-colored.” The exact opposite of what you’d think!

These larval worms become sphinx or hawk moths. Both are large, jet-shaped moths with dull, mottled gray wings and bright red to yellow spots on their abdomens. They usually appear at night. You may also see them at dusk or dawn hanging around tomato plants —where they lay their eggs on the underside of tomato leaves.

While they prefer tomato plants, hornworms also will feed on green tomatoes and pepper plants.

Not sure what insects you’re seeing in your vegetable garden? Check out Extension Publication 2347, “Insect Pests of the Home Vegetable Garden.”