Tomato Hornworms

How to Identify and Get Rid of Tomato Hornworms

Tomato Hornworm
Amanda Hill

Big, fat, and green! Here are tips on how to identify, control, and get rid of tomato hornworms in your garden.

What Are Hornworms?

If you’ve ever grown tomatoes, chances are good that you’ve dealt with these green caterpillar pests. There are two main garden pest species, tomato hornworms and tobacco hornworms, which can be found in most regions of the U.S. and in southern Canada. Both species can ruin your tomato crop in record time! They also feed on other plants in the Solanaceae (nightshade) family: eggplants, peppers, tobacco, and potatoes. They blend in quite easily with the green foliage and feed non-stop, creating spotty and chewed leaves and fruit.

Tomato (and tobacco) hornworms live according to the following life cycle:

  • In late spring, large adult moths lay eggs on the undersides of foliage, which will hatch within a week. The adult moths are easily recognizable; they’re commonly called sphinx or hummingbird moths.
  • Caterpillar larvae will hatch in late spring and feed for 4–6 weeks before creating a cocoon, overwintering in their pupal state in the soil. If the weather is warm enough, larvae may only burrow for as little as 2–3 weeks.
  • Moths will emerge in the spring, and will then lay eggs once again. More than one generation a year may be possible in warmer climates.

Tomato hornworm moth (female). Photo by Didier Descouens.
Tomato hornworm moth (female). Look out for the moths in late spring. Photo by Didier Descouens/Wikimedia Commons.

Identification

How to Identify Tomato Hornworms

Hornworms can be up to 5 inches long—which can be quite a shock when you first come across one! They do the most damage in the caterpillar—or larval—stage. They are pale green with white and black markings, plus a horn-like protrusion stemming from their rear. (Don’t worry, they aren’t able to sting or bite!) The caterpillar also has eight V-shaped stripes on its green body. Tomato hornworms come from a mottled brown-gray moth (see picture, above). 

    The larvae blend in really well with the plant greenery. Just get used to a daily patrol, looking for hornworm eggs and small caterpillars. Here are some cues of infestations:

    • Hornworms tend to start feeding from the top of the plant; look for chewed or missing leaves.
    • Look closely at the TOP of your tomato leaves for dark green or black droppings left by the larvae feeding on the leaves. Then look at the underside of leaves and you’ll likely find a hornworm.
    • Look for stems missing some leaves and wilted leaves hanging down. You may find white cocoons and their hornworm hosts nearby.

    Tomato Hornworm. Photo by Amanda Hill.
    Tomato hornworm

    Tomato vs. Tobacco Hornworms

    There are a few species of hornworms that inhabit North American gardens, including tomato hornworms (Manduca quinquemaculata) and tobacco hornworms (Manduca sexta). Both species feed on common garden plants like tomatoes, potatoes, peppers, and eggplants. Here’s how to tell which caterpillar is which:

    • Tobacco hornworms have parallel white stripes; tomato hornworms have white V–shaped markings.
    • Tobacco hornworms have black spots lining each of their stripes; tomato hornworms do not.
    • Tobacco hornworms have a red “horn” on their tail end; tomato hornworms have a black horn.

    tomato-worms-hornworms.jpg
    Can you tell which hornworm this is? (It’s a tobacco hornworm! Notice the white stripes with dotted black lines and a red “horn.”) 

    Tomato Hornworm Damage

    If you see leaves with large holes and severe defoliation, devoured flowers, and/or scarring on fruit surfaces, you might have tomato or tobacco hornworms. The fruit also may be damaged by sunscald because of the reduced foliage cover.

    Control and Prevention

    How to Get Rid of Tomato Hornworms

    • Handpicking is an excellent tactic for control if you have the time and patience, or a small garden. The caterpillars are not dangerous and can neither sting nor bite. If you are squeamish about crushing these large insects, drop them into soapy water instead (or feed them to your chickens, if you’ve got a flock).
    • If the hornworm population or the area of your garden is too large, insecticides can be effective, though they should be a last resort. You can use the organic pesticide Bt (Bacillus thuringiensis), which is a bacterium that acts as a stomach poison on some larval insects (but doesn’t harm other plants or animals). Bt must be ingested by the caterpillars to be effective, and it must be reapplied to plant foliage after rain. Please check with your local Cooperative Extension for a list of approved insecticides in your area.
    • Insecticidal soaps will also kill hornworms, but the pests need to come into direct contact with the substance.

    get-rid-of-hornworms.jpg
    A tobacco hornworm covered with parasitic wasp eggs. 

    How to Prevent Tomato Hornworms

    • Till soil at the beginning and end of each gardening season to destroy overwintering larvae. Tillage has shown to cause up to 90% mortality.
    • Keep wasps around; a number of species are beneficial insects which feed on hornworms and act as a biological control. You may see hormworms with parasitic wasp larvae attached, which look like grains of rice (see picture, above). These attacked hornworms will continue to feed for a little while, but will soon succumb to their hitchhikers, so it’s wise to leave them alone and let the wasps carry out their life cycle. Alternatively, remove infected hornworms and place them far away from your garden. This way, the wasps will still do their job, but the hornworm won’t continue to damage your crops. 
    • Other beneficial insect, like ladybugs and green lacewings, may feed on young hornworms or hornworm eggs.
    • To keep hornworms away from your tomato plants next year, try interplanting dill or basil; marigolds are also an excellent companion plant.

    See the Almanac Garden Pest and Disease Library for more information on common pest problems.

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    Reader Comments

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    Hornworms

    We interplant Basil with our tomato's and have not had a problem for about 5 years

    i have a moon flower plant

    i have a moon flower plant that appeared out of nowhere about 3-4 months ago. today my wife discovered the tomato hornworm on the underside of some leaves, is this something that attracts them?

    The tomato hornworm

    The Editors's picture

    The tomato hornworm caterpillars can be found on tomatoes, potatoes, eggplants, moon flowers and tobacco plants. The hawkmoth is attracted to the moon flower and lays its eggs on the leaves.

    I read them ALL :-) Some

    I read them ALL :-) Some cute, some frighting, a couple made me laugh.

    For the first time in YEARS I have horn-worms! And a lot of them. I live in No. Nevada for 13+ years now and this is only the Second time I have gotten these worms. They are eating my Tomatoes, Potatoes (on the other side of the house LOL) and my Bell pepper plants! I am having a VERY hard time keeping up with them!

    I normally NEVER apply ANY kind of pesticides on my garden, but will be trying the "Natural" remedies posted on here.

    I too have ALWAYS done companion planting, lots of basil and Mary Gold flowers (I read long ago Mature Dill isn't good for the tomatoes) and yet I still have those HUGE green Ninjas. This morning as I was checking the plants one little, sorry, Big bugger reared up LOL chop-chop LOL cute. Hated to snag him, but want my tomatoes more :-)

    I'm wondering IF all the rain we got (see flash flooding) of resent is why I have them this year.? We have been in a drought for Sooo long I had gotten use to minimal predatory insects that infest my garden...Aphids always bad, this year not so much :-)

    I ALWAYS til the ground up... a Few times before the plants go in the ground. This year I grew all be three plants by seed...It was so wonderful :-) and the weather just wasn't with me this year. Normally I have the best garden around.

    Is it possible for the worms/larvae to stay in the ground for more then one year? And is it possible that even with REALLY good tilling they are still hidden really well in the ground?

    I couldn't find any Borage seeds to grow. Next year I am going to have to buy a Lot of this plant.

    One more Q: Can I grow Borage from seed?

    I've had problems every year

    I've had problems every year with tomato worms in New Mexico. Picking them off is time consuming but the only effective solution I've found. This year I bought a black light flashlight from Amazon ($15.00) and checked my plants after dark. My wife and I can't believe how effective it is. They show up great. We now appear to be free of the tomato worms. Just thought I would pass this info along.

    You can plant Borage in

    You can plant Borage in between tomato plant. And you should not have any more worms..

    I live in Charleston, & I had

    I live in Charleston, & I had never heard of a hornworm, much less seen one. I must say that it scared me! Huge! It decimated my whole Cherokee crop in 2 days by ITSELF. I've never encountered such destruction! They may be kinda "cute", but beware: they will destroy all your hard work. We named him "Ivan" because of the eye-like markings on his sides, & whisked him off to the back yard before he could start on my bell peppers.

    Not sure what u have going

    Not sure what u have going on. I'm thinking it's horn worms. I only have one plant now the other one I had died. But I'm noticing curled up leaves with tiny green worms. And a lot of eaten leaves, even cut flowers with a kind of web.around the worms. What are they and how can I get rid of them. I don't want to lose my plant?

    Hi, Joshua, We hate to see

    The Editors's picture

    Hi, Joshua, We hate to see you lose a plant but we're not sure what this might be. Usually any worm on a plant is a problem, so pick them off if you see them. Tiny green worms could very well become large green worms—hornworms!—and you don't want those, so eliminate the little and large things. You could also soak the plant in a pyrethrum solution. This is a safe pest repellant. (It worked two years ago when little white worms appeared all over my tomatoes.) Follow directions for mixing and really soak the plant.
    We hope this helps.

    Just anecdotal in nature:

    Just anecdotal in nature: located in Central Washington, I had a great year for tomatoes and eggplant one year.The new garden had been planted where alfalfa had previously been grown. Then the horned worms hit. They were everywhere. I picked half of a 3Lb coffee can full of them. I tossed one to the chickens and they went nuts for it. So, I tossed all of them in with the chickens. They loved them, running around stealing the worms from each other. The next morning all but one of 20 chickens were dead. There was no other variable changed other than the worms.

    Oh, no! Nobody else here

    The Editors's picture

    Oh, no! Nobody else here appears to have had that happen to their chickens, Dan. How terrible and shocking to find. We are so sorry.

    I never fed that many worms

    I never fed that many worms to my chickens, and all the ones I did feed them never affected them one way or the other. Sorry for your loss.

    Tomatoes are in the night

    Tomatoes are in the night shade family which is very toxic to chickens. The fruit is ok, but the stems and leaves are poisonous to chickens. The worms eat only the leaves and stems... That's why the chickens died. So sorry for your loss

    I planted some tomato plants

    I planted some tomato plants in our garden this year (first time growing a garden), and this morning, I saw a caterpillar eating through the stems of my plants.

    This had happened with the other plants, but I never saw a caterpillar until now.

    What's weird about this caterpillar is this it only eats through the bottom of the stem- but it leaves the rest of the plant intact. Could it be a "regular" caterpillar, or maybe a hornworm? It didn't look like a hornworm in any way, however.

    Thanks in advance.

    Perhaps it is a cutworm?

    The Editors's picture

    Perhaps it is a cutworm? These are usually nocturnal, but they cut through the base of young plants. Check this page for more information and photos:
    http://www.almanac.com/content...

    That would be cut worms they

    That would be cut worms they attack the stem of small plants

    I have found neem oil to be

    I have found neem oil to be very effective,for horn worms, and other leaf eating and sucking insects. It is probably the safest.
    It is not instantaneous. It causes worms to forget to eat,as well as many other symptoms. It is not harmful tobeneficials, because they dont eat or suck the leaves. youmight smother them though, so spray later in day, when they're not active. I live in sacramento, it gets quite hot here summmertime, no adverse effects so far, on my tomatos. most organic treatment I think.

    you don't even need protective clothing. It is effective in very small concentrations.

    I would feed any I pick to my

    I would feed any I pick to my chickens and watch the madness ensue. So far I have not had any horn worms but the stink bugs were a real menace this year. Perfect tomatoes with little black dots and they taste bad wherever they are poked at.

    Ended up having half a harvest due to a watering issue and the stink bugs. I think better weed control would have helped.

    My tomato plants are healthy,

    My tomato plants are healthy, and produced many flowers and tomatoes. They were so heavy with tomatoes that the cages fell over and had to be propped up. As I pick the tomatoes, I'm finding about half of them have a little black worm in them. I've seen these around the yard all the years I've lived here, and this is the first time I've seen them in the tomatoes. The live worm curls in a circle and it's about 1/3 inch long. The beefsteak tomatoes are ruined and half the Romas are infested. The cherry tomatoes have a few, but they fared the best.
    How do I protect against these in the future? They've never been a problem in the past

    Hi, Donna, It sounds like the

    The Editors's picture

    Hi, Donna,
    It sounds like the tomato pinworm. These overwinter in soil, especially that of greenhouses. The first recommendation is "clean soil." (Don't we all think we've got clean soil?) Essentially, if you buy transplants, get your tomatoes from a trusted source. Keep your garden clean last season's plant refuse. Rotate your crops.
    If you see evidence again (small holes in the leaves, for example), remove the leaves from the plant. If you see holes in the tomatoes in season, use any that are edible and dispose of the remainder.
    We hope this helps.

    I'm in the Boulder, CO area

    I'm in the Boulder, CO area and I've never seen hornworms as big as here! Moved here from Illinois last year and had them there, too. I have Marigolds all over the place right next to the tomatoes and basil less than a foot away - tons of it. Nothing helps except picking them off although I haven't tried the Bt stuff - afraid to!

    Last year when I noticed that

    Last year when I noticed that I had tomato hornworms feasting on my tomatoes, I picked and destroyed what I could find. Later, after dark, I went out in the garden armed with a blacklight on an extension cord, and lo and behold those that I missed lit up like neon lights among the leaves! Easiest way I know to get rid of the little beasts!

    Just had to share: My

    The Editors's picture

    Just had to share: My community garden has been plagued with hornworms for years. This year not so: I saw only two on my plants, and each was covered (and so destroyed) by tiny white wasp cocoons.
    To attract parasitoid wasps, provide beneficial plants nearby, such as those in the carrot or cabbage families. Specifically you could include sunflowers, coriander, cornflowers, sweet alyssum, and asters.
     

    I just seen one for the first

    I just seen one for the first time today and was bigger then a bic lighter and long ..

    I also just saw my first one

    I also just saw my first one ever!! Thought it was some kinda mutant caterpillar lol

    bT is safe and it works. One

    bT is safe and it works. One bite and they stop feeding. It works on all kinds of caterpillars, not just hornworms. Spray seems to not be the problem since you can wash it off,and it is in the soil naturally in small amounts, but when it is used in corn or other seeds as a GMO not so sure that it is safe.

    You wrote earlier by saying:

    You wrote earlier by saying: "don't crush them", why not? When I found one on one of my tomato plant, I sniped him in two. Is there a consequence?

    I'm curious about this as

    I'm curious about this as well. Why not crush them? Prior to reading this, I found one and I did crush it - will it attract others or something?

    Other than it being a icky

    The Editors's picture

    Other than it being a icky job that could leave a stain, it is OK to crush them; it is a popular control method. For those who are squeamish about crushing so large an insect, though, dropping them into soapy water is less gooey. We'll revise the article so that it is clearer. Thank you!

    Today I found several leaves

    Today I found several leaves of my potted tomato plant eaten...there were several "horn worms" attached to the branches, so with a long handled pair of plyers I pulled them off and dropped them in a bucket...I then sprayed the plant with liquid "Sevin"...about an hour later I found several large and small worms laying on top of the soil in the pot...by the way I also sprayed the ones in the bucket and they were dead...

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