Tomato Hornworms: How To Get Rid Of Tomato Hornworms


This post may contain affiliate links, my full disclosure can be read here.

How to get rid of tomato hornworms naturally and quickly! Hornworms are big green caterpillars that are commonly found on tomato, pepper, and potato plants.

They can cause a lot of damage to your plants but the good news is you really can control them and save your garden.

I think that tomato hornworms are one of the creepiest pests to find in your backyard garden.

I still remember being very surprised the first time I found one eating my tomato plants.

Left untreated hornworms can quickly become a big problem in your garden eating the leaves, stems and even baby fruits of your plants.

Top photo a tomato hornworm Photo credit Whitney Cranshaw, Colorado State University, Bugwood.org. Bottom photo tobacco hornworm.

But if you take a minute to learn their lifecycle so that you can spot them in the early stages quickly you can prevent damage to your plants.

Even if it’s already started you can kill the hornworms in your garden and your tomato plants can recover.

What Are Hornworms?

Close up of a tomato hornworm feeding on a tomato plant. Photo credit Whitney Cranshaw, Colorado State University, Bugwood.org.
Close up of a tomato hornworm feeding on a tomato plant. Photo credit Whitney Cranshaw, Colorado State University, Bugwood.org.

If you’ve been growing tomatoes for a while there is a good chance that you’ve had to deal with these big green caterpillars in your garden.

There are two types that are the main pest for gardeners in Canada and the U.S.A. These are the tomato hornworm (Manduca quinquemaculata) and tobacco hornworm (Manduca sexta) both are a nasty pest and can cause a lot of damage to your tomato crop quickly.

In addition to tomatoes, they also feed on other plants in the nightshade (Solanaceae) family including peppers, potatoes, eggplants, and tobacco.

Identification

Tomato hornworms can grow up to 5 inches (12.7 cm) long compared to most caterpillars we are used to seeing in the garden it can be quite a surprise when you first notice this pest!

Hornworm caterpillars are pale green in color with white or cream-colored lines on their sides and black and cream dots running along their side.

They also have a horn that looks somewhat like a thorn prod trueing from their rear giving them the name hornworm. Don’t worry as creepy as this pest can look they don’t bite or sting.

Lifecycle

The adult hawkmoth, sometimes also called a sphinx moth is a large moth with mottled grey-brown wings. Along its abdomen are yellow spots. With its wings extended its wingspan can be 4-5 (10.16-12.7 cm) inches wide.

Adult hawkmoth (tomato hornworm moth) feeding on pink petunias.
Adult hawkmoth (tomato hornworm moth) feeding on pink petunias.

The hawkmoth loves to feed on trumpet-shaped flowers and is often mixed up with the hummingbird moth because their caterpillar is similar in appearance.

In the late spring, the females lay their eggs on both the top and bottom of leaves of plants in the nightshade family.

The eggs are very small in size, oval-shaped and pale green to yellow in color. They hatch in only 6-8 days.

As the caterpillar goes through 5-6 growth stages called instars their appearance changes a lot.

When the young caterpillars hatch they are in the first instar and are white to yellow in color with no identifiable markings.

Mature tomato hornworm caterpillar. Photo credit Whitney Cranshaw, Colorado State University, Bugwood.org.
Mature tomato hornworm caterpillar. Photo credit Whitney Cranshaw, Colorado State University, Bugwood.org.

As they grow and shed their skin they start to take on the well-known hornworm appearance.

In the later instars, they have 8 white V-shaped makes running laterally along their sides. A black or dark blue horn grows out of the last segment of their abdominal.

It takes 3-4 weeks for them to reach the final instar stage by this time the hornworm is 3 1/2 to 5 inches (8.89-12.7 cm) long. They then fall off the plants and burrow into the soil.

In the summer they will pupae in about 2 weeks when new moths emerge, breed and start the cycle over again.

The late summer generations will puppet in the soil over winter and emerge the following spring.

Tomato Hornworms VS. Tobacco Hornworms

Top photo: Tomato hornworm has white V-shaped stripes pointing towards the front of its body with a black or blue horn. Photo credit Whitney Cranshaw, Colorado State University, Bugwood.org. Bottom photo: Tobacco hornworm has diagonal white lines with a thin black edging and a red horn.
Top photo: Tomato hornworm has white V-shaped stripes pointing towards the front of its body with a black or blue horn. Photo credit Whitney Cranshaw, Colorado State University, Bugwood.org, photo modified to add text. Bottom photo: Tobacco hornworm has diagonal white lines with a thin black edging and a red horn.

There are a few types of hornworms you may find in your garden including tomato hornworms (Manduca quinquemaculata) and tobacco hornworms (Manduca sexta).

Both types feed on nightshade vegetables in your garden causing damage.

You can tell them apart with these tips:

  • Tomato hornworms have white V-shaped markings whereas tobacco hornworms have parallel white stripes.
  • Tomato hornworms have a black horn, tobacco hornworms have a red horn.
  • Tobacco hornworms have black spots along the edge of the white strips on its side and tomato hornworms don’t have these spots.

Tomato Hornworm Damage

Hornworms are a garden pest that causes a lot of damage quickly. They will eat entire leaves, stems, and even green immature fruit. If left to feed on the plants they can defoliate it in just a few days.

But because of how they blend into the plant with their light green color you’ll often notice the plant damage first before you find the caterpillars on your plants.

Hornworms normally start feeding on the top of the plant so that’s the best place to start looking for damage.

Start by looking closely at the top of your tomato plants for droppings left behind by the caterpillars as they feed, they will be black or dark green in color.

If you see this then turn the leaves over and you will often find a hornworm hiding on the other side.

You’ll also want to look for white cocoons of hornworms that haven’t yet hatched.

Organic Control To Get Rid Of Tomato Hornworms

1. BTK

The easiest way to get rid of and prevent hornworms on your plants is to use the organic pesticide BTK (Bacillus thuringiensis). This is made from a natural bacterium found in soil that is toxic to caterpillars.

However, it must be ingested by the caterpillars to work and needs to be reapplied after it’s rained as it’s easily washed off the leaves.

BTK has always been the quickest and easiest way for me to get rid of hornworms in my garden.

Simply spray it on the plants as a preventative or start spraying when you see damage starting on the tops of the plants.

Very quickly the caterpillars will die off.

2. Handpicking

Pick hornworms off your plants and into a container. Feed them to your chickens or drown in soapy water.
Pick hornworms off your plants and into a container. Feed them to your chickens or drown in soapy water.

Handpicking is an easy way to get rid of hornworms on your tomato plants. Since the caterpillars are so large they are easy to pick off the plants.

If the idea of squishing these pests makes you cringe then try dropping them into a container of soapy water instead.

Another alternative is to feed them to your chickens if you keep a backyard flock.

3. Insecticidal Soaps

Insecticidal soaps are also a good way to kill hornworms but they have to come into direct contact with it to work.

This means you need to spray the plants often and make sure to get under the leaves as well.

4. Diatomaceous Earth

Diatomaceous earth is a natural powder made out of fossilized diatoms that turn into a soft sedimentary rock. This organic powder is a natural pest solution that I love to use in the garden when needed.

Simply sprinkle a little over your plants and it will kill most bugs that crawl through it in a few days.

However, you should keep in mind that since it kills all bugs not just the pests you need to be very careful in how you use it.

Avoid using it if your plants are flowering as it can also harm bees. But earlier in the season before they have started to flower it’s a helpful method.

How To Prevent Tomato Hornworms

Dealing with a pest problem in your garden quickly is good but it’s always better if you can prevent a problem in the first place.

There are many things you can do to help prevent tomato hornworms from making a home in your vegetable garden.

1. Beneficial Insects

Tobacco hornworm covered in parasitic wasp eggs.
Tobacco hornworm covered in parasitic wasp eggs, the same wasps feed on tomato hornworms too.

Encouraging beneficial insects like parasitic wasps in your garden helps a lot with controlling pests naturally.

If you find caterpillars in your garden that have white egg sacks along its back it’s best to leave it alive, but you can remove it from your garden and place it in an out of the way area far from your plants.

These egg sacks are from a parasitic wasp that feeds on caterpillars in your garden. When they hatch you will have many more beneficial wasps helping to control caterpillars in your garden.

Ladybugs and green lacewings are other natural predators for pest control in your garden.

Try creating a welcoming environment for these helpful insects you can even purchase them to add to your garden for a head start.

2. Companion Planting

Try companion planting to help discourage pests around your tomato plants. Growing marigolds, basil or dill as companion plants can really help with pests.

3. Tilling

Since hornworms overwinter in the soil tilling in the fall can help to kill off most of the overwintering larva.

But if you are a no-till gardener like we are another good option is to let your chickens into your garden in the fall. They do a wonderful job of scratching up the ground and eating bugs hiding in the soil.

Although tomato hornworms can cause a lot of damage quickly in your garden they really are easy to prevent and control naturally if you start treatment early in the season.

More Tomato Growing Tips

Naturally Get Rid Of Hornworms text overlaid on a photo collage top image is a hornworm eating a tomato plant, lower left a hornworm with parasitic wasp eggs, lower right an hawkmoth.
How To Get Rid Of Tomato Hornworms text overlaid on a close up photo of a hornworms on a tomato plant
Fully grown tomato hornworm on a tomato leaf. Photo credit Whitney Cranshaw, Colorado State University, Bugwood.org. Photo modified to add text.

Add a Comment

Your email address will not be published. Required fields are marked *