Tomato Hornworm: How to Identify It, Find It, and Get Rid of It

What is a tomato hornworm?

A tomato hornworm is the caterpillar of a large moth, the five-spotted hawk moth (Manduca quinquemaculata). It grows up to 4 inches (10 cm) long and about 1/2 inch wide, with eight white V-shaped marks on each side of a green body. It gets its name from the dark, pointed horn on its rear end.

This caterpillar feeds only on plants in the nightshade family. Tomato comes first, but it also eats pepper, eggplant, potato and tobacco leaves. It feeds on weeds such as horsenettle and jimsonweed too, according to the University of Wisconsin, the University of Minnesota and BAMONA. Only the caterpillar does damage. The adult moth drinks nectar from flowers and leaves your plants alone.

There is a catch in the name, though. The tomato hornworm has a close cousin, the tobacco hornworm (Manduca sexta), that looks almost the same and eats the same plants. In much of the United States, the big green caterpillar on a tomato plant is more likely to be the tobacco hornworm. The next section shows how to tell the two apart.

Both are hornworms, the name for the caterpillars of sphinx moths, also called hawk moths (family Sphingidae). Colorado State University counts more than 30 kinds of hornworm in Colorado alone, and says only these two are pests of vegetable gardens there.

Tomato hornworm vs tobacco hornworm: which one do you have?

Count the white marks and check the horn. A tomato hornworm has eight V-shaped marks on each side and a straight black or dark blue horn. A tobacco hornworm has seven straight diagonal stripes, edged in black, and a curved red horn. Rutgers suggests a memory trick: V8, for eight Vs, like the tomato juice.

Markings and horns from Clemson, Illinois Extension, UF/IFAS, UMass and Wikipedia. Moth spots from UF/IFAS and BAMONA. Range from BAMONA and UF/IFAS.

Why most “tomato hornworms” are tobacco hornworms

Despite its name, the tomato hornworm is often not the one people find. UF/IFAS says it is uncommon in the Southeast, and that hornworm damage on Florida tomatoes is typically the tobacco hornworm. Extension services from Maine to Colorado say much the same, as the table shows.

Does it matter which one you have? Not for your plants. Both eat the same crops, follow the same life cycle and respond to the same controls. Wikipedia also points out that the host plant tells you nothing, since either species turns up on tomato or tobacco. One fun difference: on wild tobacco, tobacco hornworms breathe out a little of the nicotine they eat, and the Max Planck Institute found that this “toxic breath” keeps wolf spiders away.

What tomato hornworms look like at every stage

A tomato hornworm goes through four stages. It starts as a round green egg about 1/16 inch across and hatches as a tiny caterpillar that grows to 4 inches. Then it turns into a brown pupa 2 to 2 1/2 inches long in the soil, and comes out as a moth with a 4 to 5 inch wingspan. Only the caterpillar eats your plants.

Tomato hornworm eggs

The eggs are smooth, round and about 1/16 inch (1 to 1.5 mm) across. Clemson says they start light green and turn white just before they hatch. The moth lays them one at a time, at dusk or at night, mostly on the undersides of leaves. Minnesota and Rutgers note that some end up on the top of the leaf instead.

Each moth leaves only one to five eggs per plant visit, according to Oklahoma State and Clemson, so you rarely find more than a few on one plant. Over her life, though, a female can lay up to 2,000 eggs, Oklahoma State says. In summer heat they hatch in about 4 to 7 days.

Baby hornworms

Young hornworms are tiny, about 5 mm (1/5 inch) long, according to Kansas State. Minnesota describes small ones as yellow to white with no markings. Their horn looks huge for their size: a University of Wisconsin lab that raises them says it is often longer than the body at first.

Baby hornworms stay on the leaf where they hatched and feed there, UF/IFAS says. Kansas State calls them nearly impossible to find at this size. Still, this is the best time to catch them, so look for small chewed holes in the top leaves and check the undersides nearby.

Full-grown hornworms: green, brown or nearly black

A full-grown hornworm is 3 to 4 inches (7.5 to 10 cm) long. Most are bright green or blue-green, which hides them well among tomato leaves. Some are not green at all. Michigan State describes a dark, nearly black form of the tomato hornworm, though Colorado State says darker forms are less common. UMaine adds that tobacco hornworms are sometimes brown.

A hornworm that changes color may be about to pupate. Hornworm keepers on Reddit describe a duller yellow-green body with a dark line across the back. Once it stops eating, it leaves the plant to dig into the soil. The University of Wisconsin lab sees brown bars appear behind the head about 12 hours before it turns into a pupa. On the other hand, a brown horned caterpillar on grape or Virginia creeper is probably a different sphinx moth, so see the look-alikes near the end of this page.

Hornworm pupa

The pupa is a hard, shiny shell, mahogany to dark brown and 2 to 2 1/2 inches long, according to Kansas State. One end has a curved loop that looks like the handle of a jug. UMass and UF/IFAS explain that the loop holds the moth’s long tongue while it forms. You find them 3 to 6 inches down in the soil when you dig or till in fall or spring.

Each one is a hornworm moth waiting for next summer. If you want fewer hornworms, crush it, or leave it on the surface. Rutgers notes that pupae exposed by spring digging die from the weather. If you would like to watch one turn into a moth, keep it in a container of soil.

The moth: five-spotted hawk moth and Carolina sphinx

The adult is a heavy, gray-brown moth with narrow wings that span 4 to 5 inches, says the University of Minnesota. It hovers in front of flowers at dusk, beating its wings so fast that people often take it for a hummingbird. That is why people call it a sphinx moth, a hawk moth or a hummingbird moth. It sips nectar through a tongue that Kansas State says can reach 4 inches.

To tell the two moths apart, count the yellow-orange spots along each side of the body. The tomato hornworm’s moth, the five-spotted hawk moth, usually has five pairs. The tobacco hornworm’s moth, the Carolina sphinx, usually has six, according to UF/IFAS and BAMONA. Both visit petunias and honeysuckle, and BAMONA also lists moonflower for one and phlox for the other. In the Wisconsin lab, adults live about a week.

Tomato hornworm life cycle

Hornworms spend the winter as pupae in the soil. Moths come out in late spring and lay eggs on tomato plants, and the caterpillars feed for about 3 to 4 weeks before they burrow down to pupate. In much of the country this happens twice each summer. In the far South it can happen several times between spring and fall.

Timing from Clemson, Rutgers, Minnesota, UMass, Kansas State, the Missouri Botanical Garden and the University of Wisconsin. Every stage runs faster in hot weather and slower in cool weather.

Why hornworms seem to appear overnight

Nearly everyone who grows tomatoes asks this one: no hornworms yesterday, a giant one today. In fact, it was there the whole time. A newly hatched one is about 5 mm long, and Kansas State says small larvae are nearly impossible to find. Most people only spot them in their last few days of feeding.

Growth is the second reason. Minnesota says the last caterpillar stage eats nearly as much as all the earlier stages put together. So the caterpillar and the damage both seem to explode in the final week. Illinois says one or two large hornworms can strip a five-foot tomato plant in under three days.

That is why the small signs matter: a few chewed leaves at the top, or the first small droppings. Catch a hornworm then and you save most of the plant.

When to look for tomato hornworms where you live

How many times hornworms come back each year depends on the length of your summer. Use this table to know when to start checking.

Why do they stop in fall? Day length decides it. The University of Wisconsin lab found that caterpillars raised with 12 hours of daylight or less go dormant as pupae for 8 to 9 months. With 13 hours or more, they turn into moths in about a month. So the late-summer caterpillars are the ones that sleep in your soil until spring.

Tomato hornworm damage: the signs to look for

Hornworms eat leaves from the top of the plant down, leaving bare stems and leaf veins behind. They also take big bites out of green tomatoes, leaving open scars rather than holes that tunnel in. The surest sign is their droppings: large, dark green to black pellets on the leaves and the ground below.

• Missing leaves at the top. Minnesota says they start feeding on the upper parts of the plant.
• Bare stems and veins. Oklahoma State describes plants with stems and leaf veins left but the leaf surface gone.
• Chewed flowers and stems. Rutgers adds blossoms and stems to the menu.
• Open scars on green fruit. Clemson and Oklahoma State say they feed on the surface of the fruit instead of boring in.
• Droppings shaped like tiny stars. Rutgers says the pellets can look like small stars or flowers. Darker ones may be older, so the caterpillar may have moved on.

Fruit damage is the smaller problem. Clemson notes it is much less common than leaf loss. Even so, a bitten tomato is often a lost one. UF/IFAS says fed-on fruit will not mature properly, and Wisconsin says it may rot on the vine or dry into a hard scar.

Hornworm damage or something else?

Several tomato pests leave damage that looks alike at first. This table sorts them by the clue you can see.

Fruitworm, spider mite and aphid details from Clemson HGIC 2218. Stink bug and leaf-footed bug details from Clemson and our leaf-footed bug guide.

Pale blotches with no holes come from sucking bugs, and our guide to the leaf-footed bug on tomatoes shows how to tell it from a stink bug. Fine speckling points to spider mites, and curled, sticky new growth to aphids on your plants.

Can tomato hornworms hurt you?

No. A tomato hornworm cannot sting or bite you. The horn looks like a stinger, but Kansas State University says it cannot sting or puncture skin. Poison Control explains that caterpillar stings come from venomous spines or bristles, and a hornworm has none. You can pick one up with bare hands. Many people use gloves anyway, because a big one grips the stem hard and squirms.

If you handle one, it may thrash from side to side and spit up green fluid from its gut, Kansas State says. That is all it can do. Wash your hands afterward, as you would after any garden work. Since the horn cannot sting, a hornworm is safe for a curious child to hold.

If a toddler or a pet swallows one, Poison Control says the main risk with any swallowed caterpillar is choking. When nothing gets stuck, reported cases of children swallowing caterpillars have not led to serious problems.

How to find tomato hornworms on your plants

Follow the droppings. Fresh, dark green pellets on a leaf mean the caterpillar is right above them. Next, look at the stems where leaves have vanished, near the top of the plant. Check at least twice a week in summer, as Minnesota advises, and search in the early morning or at dusk, when they feed on the outside of the plant.

Colorado State says hornworms tend to feed at dusk and dawn on the outer parts of the plant, which makes them easier to see then. By day they sit along the stems and under the leaves. Rutgers suggests shaking the plant over a sheet of cardboard or paper and checking what falls. Check your peppers, eggplants and potatoes too.

Use a UV flashlight at night

Hornworms glow under ultraviolet light. Shine a UV (black light) flashlight over the plants after dark and the caterpillars light up bright green, while the tomato leaves turn a deep red-orange, Illinois Extension says. UMass and Mississippi State recommend it too, and small UV flashlights are cheap.

It does not work for everyone. In the Almanac’s comments, one gardener found about 40 more hornworms with a black light, while another could not make them stand out at all. Gardeners on Reddit who report the best results use a true UV light, often sold as 365 nm, in full darkness. Cheaper 395 nm lights give off more visible purple light, which can wash out the glow. We found no study that compares the two, so treat that as gardeners’ experience.

Should you kill tomato hornworms?

Usually yes, if they are on plants you want to harvest. A few hornworms can strip a plant in days, and Michigan State calls handpicking safe and effective. There are two exceptions. Leave any hornworm covered in small white cocoons, because those wasps will kill more hornworms. And if you would rather not kill them, you can move them.

Based on Illinois Extension, Michigan State, Minnesota, Oklahoma State, Wisconsin, Rutgers and the Missouri Botanical Garden.

Moving them works, with one honest caveat: a moved hornworm still becomes a moth, and that moth may lay eggs on your tomatoes next summer. If you want to share, some gardeners on Reddit grow one spare tomato plant just for the hornworms.

The white things on a hornworm’s back: wasp cocoons, not eggs

The white, rice-like things on a hornworm are not eggs. Mississippi State entomologist Blake Layton explains that they are the cocoons of a tiny black wasp, Cotesia congregata. The wasp lays 60 to more than 100 eggs inside a small hornworm. Its larvae feed inside for about 12 days, then chew out and spin those cocoons on the skin.

By then the hornworm is doomed. Illinois and Clemson say a hornworm with cocoons has stopped feeding, and Michigan State says it dies when the wasps come out. Each wasp cuts a round lid in its cocoon and flies off to find more hornworms, UMass explains. So leave it on the plant. Some extension photo captions still call the cocoons “eggs”, which is part of why the myth sticks.

What are hornworms good for?

Quite a lot, once they are off your tomatoes. The moths are pollinators. Hawk moths are the main pollinators of sacred datura, according to field studies summarized on Wikipedia. Evening primrose and four o’clocks depend on them too. Birds and paper wasps eat the caterpillars, and the Cotesia wasp needs them to breed.

They are native, not invasive. Both species belong to the Americas, and the Butterflies and Moths of North America project (BAMONA) rates both as secure. That is why many gardeners feel torn about killing them. A popular Reddit thread on tomato hornworms drew over 200 answers from gardeners who had just learned they are native.

How to get rid of tomato hornworms

Pick them off by hand and drop them into soapy water. For most home gardens that is all you need, and the University of Minnesota calls it the most effective way to manage them. Search again at night with a UV light, leave any hornworm with white cocoons, and use Bt only if there are too many small ones to pick.

The steps below start with what costs nothing. Sprays come last, and most gardens never need them. Minnesota says pesticides are generally not necessary, and the Missouri Botanical Garden says handpicking is usually all a home garden needs.

1. Handpicking (free)

Handpicking works because hornworms are big and slow. Wear gloves if you are squeamish. Then drop them in a bucket of soapy water, cut them in half, or feed them to chickens. Rutgers adds that you can shake the plant over cardboard to catch any you missed.

Search in the early morning, at dusk, and once after dark with the UV flashlight. One search rarely finds them all, since the small ones hide so well. Keep checking twice a week until the end of the season.

2. Let natural enemies help (free)

A lot of insects eat hornworms. Lady beetles, lacewings, minute pirate bugs and spined soldier bugs eat the eggs and the youngest caterpillars, Rutgers says. Tiny Trichogramma wasps lay their own eggs inside hornworm eggs (UC IPM). Paper wasps paralyze hornworms and carry them to their nests to feed their young, and birds take them too.

You help these allies most by not spraying broad insecticides, which kill them along with the pests. Rutgers also suggests planting flowers that draw beneficial insects near the vegetable bed. Many of the lady beetles you see are on your side, including the Asian lady beetle that looks like a ladybug.

3. Bt, a spray that only affects caterpillars

Bt is a natural soil bacterium, Bacillus thuringiensis subspecies kurstaki (Btk), sold as a spray or dust. A caterpillar has to eat it, so you spray it on the leaves. It only affects caterpillars, and Minnesota says it does not harm bees or other insects. Feeding stops soon after a dose, but the Missouri Botanical Garden says the caterpillar can take several days to die.

Use it on small hornworms. Minnesota and Rutgers say it works best on young caterpillars, which need only a small dose, and UC IPM calls it effective against smaller larvae. UMass says it also works very well on large hornworms, so the advice on big ones is split. Picking those off is faster anyway. Rain and watering wash Bt off the leaves, so UF/IFAS notes you may need to apply it more than once.

Bt affects caterpillars in general, so it also kills butterfly caterpillars that eat it. So spray only the plants with hornworms, and keep it off the dill, parsley and milkweed where swallowtails and monarchs feed.

4. Spinosad and other sprays, last and only if needed

If handpicking and Bt are working, you do not need anything else. If they cannot keep up, spinosad is the next step. It comes from a soil microbe, kills caterpillars that eat it, and stays active for about 1 to 2 weeks, Minnesota says. It is toxic to bees while it is wet, though Minnesota adds that it is much less active once it has dried.

Broad sprays such as bifenthrin, cyfluthrin, cyhalothrin and permethrin kill hornworms, but they also kill the wasps and beetles that keep hornworms in check. Minnesota says they kill beneficial insects, and the Missouri Botanical Garden suggests them only when handpicking is impractical. Clemson warns not to use permethrin on tomato varieties with fruit under 1 inch across, such as most cherry tomatoes.

Every product also has a wait between spraying and picking, called the pre-harvest interval. Clemson lists 1 day for spinosad and permethrin, 3 days for carbaryl and 7 days for bifenthrin. Your product’s label has the final word.

What does not work, or is not proven

Some popular hornworm advice has nothing behind it. We found no testing for companion plants such as dill, basil and marigolds, and a study of moth light traps found they did not cut numbers enough to matter. Here is what the evidence says about the most common claims.

• Myth 1

  “The white things on its back are eggs.”

  Truth: They are wasp cocoons. Mississippi State explains that the wasp lays its eggs inside the caterpillar, and what you see are the cocoons of the next wasps. Leave that hornworm alone.

• Myth 2

  “The horn can sting you.”

  Truth: Kansas State says it cannot sting or puncture skin. Poison Control explains that caterpillars sting with venomous spines or bristles, which hornworms do not have.

• Myth 3

  “Hornworms appear out of nowhere overnight.”

  Truth: They hatch from eggs laid by moths at night, and young ones about 5 mm long are almost invisible. Then the last stage eats nearly as much as all the earlier stages combined, so they seem to arrive full size (Kansas State, Minnesota).

• Myth 4

  “Dill, basil or marigolds keep hornworms away.”

  Truth: The Old Farmer's Almanac suggests these, but none of the extension guides we read recommends companion plants for hornworms, and we found no trial. One Almanac reader even saw hornworms arrive after pulling the dill. Checking your plants still does the work.

• Myth 5

  “A black light trap will get rid of the moths.”

  Truth: Moths do fly to black light, but a 1958 study found traps did not lower numbers enough to matter, as Wikipedia notes. Kansas State adds that a moth in a trap does not mean eggs in your garden. Use the UV light to find caterpillars instead.

• Myth 6

  “Insecticidal soap or oil will kill a big one.”

  Truth: Minnesota says soap works best on small caterpillars and only on direct contact. On a 3 inch hornworm, picking it off is faster and costs nothing.

• Myth 7

  “Tomato hornworms only eat tomatoes.”

  Truth: Wisconsin lists pepper, eggplant and potato as well, plus nightshade weeds. Pepper growers on Reddit report whole plants stripped in a single day.

How to prevent tomato hornworms next year

Till or dig the bed after harvest, pull nightshade weeds, and start checking plants early. Tilling destroys up to 90% of the hornworms pupating in the soil, according to Michigan State and Illinois. Then, from early summer, check your plants twice a week, so you catch the caterpillars while they are still small.

• Turn the soil in fall or early spring. Rutgers says spring digging also leaves overwintering pupae open to the weather.
• Pull horsenettle, jimsonweed and other nightshade weeds. Minnesota and Rutgers say these weeds also host hornworms.
• Rotate where you plant tomatoes, peppers, eggplant and potatoes, as UF/IFAS advises. In a small yard this helps less, because Michigan State and Colorado State say the moths fly long distances.
• Grow flowers for beneficial insects near the vegetables, as Rutgers suggests, so wasps and lady beetles stay close.
• Start checking on time. Use the regional table above, and look closely at the top leaves.
• Skip routine spraying. Broad insecticides kill the wasps that do much of the hornworm control for free.

Growing in containers? Hornworms pupate in soil, so a pot that had hornworms may hold a pupa or two. Tip it out in fall and check before you reuse the soil.

Other green caterpillars with a horn

Many sphinx moth caterpillars have a horn, and the plant they are eating is the quickest way to tell them apart. A big green horned caterpillar on tomato, pepper, eggplant or potato is almost always a tomato or tobacco hornworm. On grape, catalpa, honeysuckle or jasmine, it is a different sphinx moth, and usually not a pest.

Host plants from BAMONA and Wisconsin Horticulture. Caterpillar details from Wisconsin Horticulture, the University of Minnesota, Mississippi State and the Missouri Botanical Garden.

Note that the white-lined sphinx can turn up on tomatoes too. Its horn is yellow or orange, and like the hornworm’s, Wisconsin says it is harmless. If you are still unsure, take a side-on photo of the whole caterpillar and run it through our free insect identifier.

When to call someone

Hardly ever, for hornworms. They are a do-it-yourself job, and a pest control company is rarely worth it in a home garden. Call your county extension office if you cannot work out what is eating your plants. Call Poison Control or a doctor if a caterpillar made your skin burn or swell, because that was a different caterpillar.

• Your county extension office for damage you cannot match to a pest, or a caterpillar you cannot name. Many take photos, like the Rutgers Garden Helpline.
• Poison Control, 1-800-222-1222, for a burning, itching or blistering rash after touching any caterpillar.
• 911 for trouble breathing, fainting, or swelling of the face, lips or tongue after a caterpillar sting.
• A doctor or urgent care for a sting that blisters, or eye irritation that does not clear, as Poison Control advises.
• A crop adviser only for large plantings, where Rutgers says spraying may make sense above one caterpillar per 10 plants.

Not sure it is a hornworm at all? Snap a clear photo of the whole caterpillar, side on, and upload it to our bug identifier by picture.

Pest control disclaimer. Photo-based identification can help, but it is not always perfect. For dangerous spiders, large infestations, or anything you are unsure about, contact a licensed pest control professional.