How To Get Rid Of Spotted Tomato Hornworms On Your Tomato Plants

As tomatoes grow tall and the yellow flowers slowly turn into small round tomatoes, another unexpected creature may appear: the tomato hornworm. You'll have to look closely as this chartreuse caterpillar with a pattern of several white V-shapes along its body blends in well when roaming along the green stems of tomato plants. Once you've spotted this pest, you'll want to take action before it harms your plant. 

What Are Spotted Tomato Hornworms

Spotted tomato hornworms or tomato hornworms are the precursor before becoming a hawk moth, also known as the hummingbird moth. They are common in North America so if you grow tomatoes, unfortunately, you’ll likely spot them on your plants. Although they’re called the tomato hornworm, they don’t only feast on tomato plants. “They have a particular affinity for plants in the nightshade family, which includes tomatoes, eggplants, peppers, and potatoes,” says Alex Kantor, owner of Perfect Plants Nursery in Florida. 

Why You Don’t Want Them on Your Plants

They are fond of tomatoes. “Tomato plants, in particular, are a favored target for egg-laying by the hawk moth [because] this allows the newly hatched hornworms to begin feeding on the plant immediately,” explains Kantor. Moths lay their eggs on the underside of leaves and camouflage well so they often go undetected unless you're specifically looking for these eggs. They hatch into caterpillars usually within a week. Often by the time you notice them crawling, three to four weeks have passed since they emerged, which is when they are full size. “These caterpillars have a voracious appetite and are known for feeding on the leaves, fruits, and stems of plants,” says Kantor. Then when it’s time to become moths, they drop off the plant and retreat into the soil before they turn into pupae. 

It’s important to be attentive and check your plants frequently to make sure these hornworms aren’t snacking on your tomato plants. “It is important to monitor tomato plants regularly for signs of hornworm infestation and take appropriate measures to control their population,” he says. 

What To Do When You Spot Them

You’ll want to act quickly when you see a hornworm.  “If you spot a hornworm on your tomato plant, my recommendation would be to promptly remove them by hand,” says Kantor. Seeing one of these caterpillars usually means there are several. “The presence of these hornworms can cause significant damage to the plant, leading to reduced harvest or even plant death,” he says. 

How to Get Rid of These Pests

There are several methods to get rid of these caterpillars from your tomato or nightshade plants.

Hand-picking

According to the University of Florida, one of the most effective ways to remove these pests is hand-picking them off the plants. Sometimes the caterpillars aren’t always easy to pull off a stem or leaf. 

Spraying with a hose

Spraying hornworms off with a hose are effective ways to get rid of them, but they are time-consuming since these methods need to be repeated at least once a day,” says Kantor.

Make a Deterrent spray

Want to deter them but not kill them? Consider making a natural spray with items in your pantry. “You can use a homemade garden spray to manage the hornworm population and a useful and effective recipe for hornworms is a mixture of cayenne pepper, water, and soap,” says Kantor. “Simply combine the ingredients, shake well, and spray regularly and directly on your tomato plants and the hornworms.” This spray will typically deter these pests but Kantor notes that it may even kill them.  

Insecticide

Sometimes there can be too many hornworms and handpicking these caterpillars isn’t possible, you can opt for an insecticide. Though using an insecticide means they will be killed. “If manually removing the hornworms is not feasible, I suggest considering the use of Bacillus thuringiensis or Bt, a natural bacteria-based insecticide that specifically targets and eliminates hornworms while posing no harm to humans or other mammals, " says Kantor.

Insecticidal soap

“You can opt for insecticidal soap, which effectively kills hornworms by suffocating them,” says Kantor.

Consider Companion Planting 

Another way to deter these pests is to practice companion planting. “This entails planting a different type of plant near your tomato plant to discourage hornworms from making an appearance,” says Kantor. “Basil is ideal to use as a companion plant since it not only repels hornworms but also enhances the flavor of your tomatoes [and] borage is an excellent companion plant since it lures beneficial pollinators and insects.” But these aren’t the only two plants to grow alongside tomatoes to deter hornworms. “Other popular companion plants that effectively deter tomato hornworms include marigolds, dill, borage, parsley, and thyme,” he says.  

Why Hornworms Are Important

Although these caterpillars can wreak havoc on your plants if you’re not attentive, they are an important part of the ecosystem. “Hornworms play a crucial role in the environment, as they serve as hosts for the parasitoid braconid wasp,” says Kantor.  Every creature has its prey and predators and hornworms aren’t an exception. Hornworms may be a nuisance and frustration for humans because they can devour tomato plants but hornworms serve as important food for the parasitoid braconid wasp.

Be prepared because how these wasps eat these caterpillars isn’t pleasant. “These wasps lay their eggs on the backs of hornworms, and as the eggs hatch, they consume the hornworm from the inside out, eventually leading to the death of the hornworm while allowing the braconid wasps to thrive,” says Kantor. Wasps are integral pollinators, such is the interconnected food web. “These wasps are essential pollinators as they feed on nectar and transfer pollen between flowers, contributing to plant fertilization and maintaining a healthy ecosystem,” explains Kantor.

Hornworms that survive and turn into moths are important pollinators for various blossoms.