How to Get Rid of Tomato Hornworms Once and for All

Vegetable gardeners everywhere look forward to harvesting tomatoes each summer. But one pest that can ruin the fruits of your labor (literally) is the tomato hornworm. The caterpillars feast on the foliage and fruit of tomatoes and other nightshades, ruining your crops before they reach maturity. To protect your plants against these garden nightmares, we’re sharing all-natural ways to get rid of and prevent tomato hornworms once and for all.

What Are Tomato Hornworms?

Tomato hornworms are the larvae of the five-spotted hawk moth. These caterpillars wreak havoc on tomato plants, damaging the foliage, fruit, flowers, and stems. “Adult moths lay eggs on the leaves of tomatoes, hatching into the caterpillars that are culpable for the damage done to the crop,” says Damon Abdi, assistant professor of landscape horticulture at Louisiana State University AgCenter. “The caterpillars consume the plant tissues until they reach their next stage of the life cycle, burrowing into the soil and becoming pupae for the next generation.” In addition to tomatoes, this insect also affects peppers, eggplants, and other nightshades.  

You can identify tomato hornworms by their bright green bodies with green-margined white stripes running down the length. Mature caterpillars can grow up to 4 inches long with a black horn at the end, says Ankit K. Singh, assistant professor of sustainable agriculture at the University of Maine. The horn is a tail-like appendage and isn’t used for defense, Singh adds.

Signs of a Tomato Hornworm Infestation

There are a few telltale signs that tomato hornworms have infested your crops. “Tomato hornworms will quickly devour foliage, particularly in the upper parts of the plant. They will also take bites out of the tomato fruit itself, if present,” says Abdi. If you notice chewed or missing foliage and fruit, chances are you have a tomato hornworm problem.

Another way to identify an infestation is by looking at the ground. “Looking down can also be a clue, as the green or black caterpillar droppings are large and fairly easy to see,” Abdi says. It can be difficult to see tomato hornworms because they blend in with the foliage, so looking for signs of damage or droppings is the easiest way to identify their presence.

How to Prevent Tomato Hornworms

These tips can prevent tomato hornworms from infesting your crops.

Plant Trap Crops

Plant trap crops, like dill or borage, that attract moths to lure them away from your tomatoes, recommends Singh. Diversifying your plantings can also increase biodiversity, welcoming natural predators that eat tomato hornworms, like lady beetles, Abdi says.

Rotate Crops

Avoid planting tomatoes or other nightshades in the same spot every year to disrupt the pest’s lifecycle, says Singh. Rotating crops reduces pest and disease issues in the garden and improves soil structure and health.

Use Row Covers

Cover tomato plants with row covers to keep the five-spotted hawk moth from reaching your crop. “Covering young plants can prevent moths from laying eggs,” Singh says.

Till the Soil

Tilling the soil in fall and spring can expose pupae hiding in the soil. “Tilling the soil is a great way to disturb the underground pupae by physically damaging them or exposing them to the environment,” says Abdi. “Tilling the soil after your tomato harvest is over can limit future generations of this pest.”

Leave Wasp-Filled Hornworms

According to Abdi, braconid wasps can parasitize tomato hornworms, laying eggs on the insect. “The cocoons look like grains of rice covering the hornworm’s back,” he says. “As they emerge from the cocoon, the wasps kill the hornworm. Leaving the parasitized hornworms in the garden will allow another generation of braconid wasps to parasitize more hornworms.”

How to Get Rid of Tomato Hornworms

If you are already experiencing a tomato hornworm infestation, use these effective treatment methods.

Hand-Pick Tomato Hornworms

One of the most effective (but time-consuming) ways to get rid of tomato hornworms is to hand-pick them. “They are large and obvious when you are looking for them, and hand-picking can keep the problem at bay before it gets out of hand,” says Abdi. “Bring a bucket of soapy water to drop them in after picking off the plants.”

Use Organic Insecticides

There are organic insecticides you can use to treat tomato hornworms. “Bacillus thuringiensis (BT) is a naturally occurring soil-borne bacterium that can be formulated into a spray,” says Abdi. “BT works great for controlling caterpillars specifically and will not pose a problem for other insects.”

Make a Homemade Spray

Homemade sprays can be effective for very light infestations, but they may not work against large, established hornworms, says Singh. To make a homemade spray, he says gardeners typically combine garlic, cayenne, dish soap, and water. Spray the mixture on the foliage of your tomato plants, testing it on one leaf first to ensure it doesn’t damage the leaves.

Use Diatomaceous Earth

Diatomaceous earth is another natural method for treating tomato hornworm infestations. “This fine powder dehydrates insects by abrading their exoskeletons,” says Singh. “While it’s more effective on crawling insects, applying it directly to stems and leaves where hornworms feed can increase its usefulness. Sprinkling it just around the plant base is less effective for hornworms but still helpful.”