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If you have been vegetable gardening for anytime at all, I am sure you have ran into a huge green tomato hornworm! I really despise these things! And with good reason, they can destroy a tomato crop literally overnight! But don’t fear, with strategic planning and some careful management you can naturally control tomato hornworms and even get rid of this horrible garden pest for good!
- Tomato Hornworm life Cycle
- How to Naturally control Tomato hornworms
- Biological Ways To Control Tomato Hornworms
- Organic Insecticide To control Tomato Hornworms
- Prevention of Tomato Hornworms
- More Gardening Tips
- Connect with Hidden Springs Homestead
- Tips for Finding the Hornworms
- Tips for Organic Hornworm Control
- 06 Aug Tomato Hornworms
- Tomato Hornworm – Organic Control Of Hornworms
- Identifying Tomato Hornworms
- Tomato Hornworm – Organic Controls to Keep Them Out of Your Garden
- How to Get Rid of Tomato Hornworms in Your Garden
- Thwarting a Tomato Caterpillar Invasion
- What Is a Tomato Hornworm?
- Tomato Hornworm Life Cycle
- Tomato Hornworms’ Habitat
- Symptoms of Tomato Hornworm Damage
- Results of Tomato Hornworm Infestation
- How to get rid of Tomato Hornworms
- Natural Predators of the Tomato Hornworm
- Tomato hornworms
- How to protect your plants from tomato hornworms
- Our Top Picks On How To Get Rid Of Tomato Worms
- What Do Tomato Hornworms Look Like?
- The Tomato Worms Life Cycle
- How Can You Find These Large Tomato Caterpillars?
- How To Get Rid Of Tomato Hornworms And Its Caterpillars?
- 9 Ways To Practice Prevention
- Vary Your Pest Control Methods
- Connect With Us!
- 1. Cultivate
- 2. Hand Picking
- 3. Light Traps
- 4. Predators and Parasites
- 5. Bacterial Insecticides
- 6. Chemical Insecticides
- How to Control and Prevent Hornworms
- Eliminating Hornworm Problems
- Fighting Future Invasions
Tomato Hornworm life Cycle
I feel like before we talk about how to get rid of tomato hornworms, we need to understand how they grow so we know what to look for. I’ve placed the life cycle in a weird way because normally, our first encounter is the full grown hornworm – at least it was for me when I started gardening.
Where do tomato hornworms come from? The hornworm life cycle is quite fascinating and goes through 4 stages: Eggs, Larvae, Pupae, and Adult.
My first encounter was in the larva stage and most likely yours as well. The big fat ugly green worm we see on our tomato plants is actually in the larvae stage called “instar 5”. I know that sounds complicated, but it really is not. Let me explain…
Think of the tomato hornworm as a large caterpiller, (Manduca quinquemaculata). It has overwintered in the soil in a large reddish-brown pupae, this is the Pupae Stage.
Tomato Hornworm Papae in Garden Soil
In the late spring, the pupae will “hatch” and a large moth emerges known as the five spotted hawk moth or sphinx moth this is Adult Stage of the tomato hornworm. The moth will feed off nectar of various flowers late in the evening until early morning, which is why we rarely see them.
During this time, moths mate and within 1-2 days the female sphinx moth will lay her eggs on plants found in the Solanaceae (nighthshade) family. These include tomatoes, peppers, egg plants, and potatoes. Of course, they are most active on tomatoes, in my opinion. The laying of eggs is the first Instar stage.
The eggs hatch within 3-5 days of being laid and a tiny green worm appears. Over the next 18-21 days, the tiny worm sheds layers of skin and grows rapidly in what is know as the 5 Instar stages.
So how big do hornworms get? Fully grown, they are 4-5 inches long! This is normally when we find them on our tomato plants. Or possibly you’ll find them by the destruction they cause on the plants. They can decimate a plant literally overnight.
You’ll most likely see the signs of the tomato hornworm, before you see the worm because it is so camouflaged with the color of the tomato plant. This will be where it has eaten the plant down to a nub or it’s large unusual hornworm poop (feces) piles on the leaves.
So how do you control hornworms? Fortunately there are several ways to naturally control tomato hornworms in an organic garden. I have tried many of these and some work better than others. Give them a try to see what works best for you.
How to Naturally control Tomato hornworms
Tilling the Soil
Since I have only raised beds, I don’t do tilling. This is not an option for me. I also don’t tilling is the best idea for creating healthy soil and harming the microbes with this process. So I can’t speak with experience to this process.
Of course, since the pupae is buried in the soil, tilling will help to destroy them before they can hatch.
As I was replacing the rotted wood walls of my raised beds, with galvanized metal, over the fall and winter, I dug up 6 pupae that had managed to bury themselves for winter. So tilling is an option for locating them and destroying them.
This is probably the most natural way of controlling them. I just really hate touching the nasty things. And I am one that has a really hard time of killing a critter or insect of any type. Though some are real garden pests like this one.
You’ll think I’m nuts, but I apologize to it and it becomes history.
Tomato Hornworms Handpicked Off Tomato Plants
The best way to find hornworms on tomatoes is to carefully look the plant over, stems, leaves on top and bottoms 2-3 times a day. Remember, they are very well camouflaged, so look closely.
I look mine over early in the morning before the sun comes over the ridge, again sometime around lunch when I’m outside busy with something else, and then again late in evening before sundown.
So about 3 times a day, I’m checking my tomato plants as well as my potatoes and peppers. I’m not saying I did the every single day, but at least 4-5 days a week. It does help a lot with control of them.
Interplanting with Beneficial Companions
What plants repel tomato hornworms? Interplanting particular plants with tomatoes will help to deter the sphinx moth from laying her eggs on your garden tomatoes. Some great ones are:
- Marigolds – they give off a strong odor that confuses the sphinx moth. Best types of marigolds to use are: Calendula (often called Pot Marigold), and the Tagetes (Grannies Garden variety) marigold
- Borage – helps to deter both hornworms and cabbage worms. The blooms also attract predatory wasps which are helpful
- Nasturtiums – these are also edible
- Basil – edible too. Small blooms also attract the Bracnoid Wasp
A trap crop is a crop that is planted near but far away enough to attract pests from the garden. A great plant to grow near by is flower tobacco plants because the sphynx moth can’t resist it.
I found a great article from the Portland Nursery for you to read and gather all kinds of great information about the flowering tobacco plants. I have never ordered from this nursery, but I did enjoy this article.
I’ll be planting flowering tobacco plants myself this season.
Crop rotation will help with controlling the tomato hornworm too if you are able to get them far enough away. I have found that in my raised beds, crop rotation is not as helpful as handpicking and interplanting.
Unlike other vegetables, tomatoes are one vegetable that prefers to be planted in the same space year after year and this is fine unless you develop a disease problem and then you will need to be sure to move them to a new location.
Biological Ways To Control Tomato Hornworms
Beneficial Insects and Natural Predators
There are 4 really helpful beneficial insects to have in backyard garden to help with controlling and preventing tomato hornworms:
Do ladybugs eat hornworms? Acutally ladybugs feed and eat on the larva of the hornworm eggs that are found on the plants.
Ladybugs feed heavily on aphid & hornworm larva and can eat up to around 50 larva a day. You can purchase ladybugs to help control tomato hornworms. If you do purchase them, they should be released at night when the are less likely to fly away.
The green lacewings works a lot like the ladybug. It too feeds of the larva of the hornworm. Green lacewings will devour over 200 or more garden pests or pest eggs in week. And yep, lacewing eggs are even available for purchase too.
Brachoid Wasp & Traichogramma Wasp
These wasps are great natural controllers of the hornworm. They lay their eggs under the skin of the hornworm and then spin a “white pill-like” cocoon over them.
When the wasp eggs hatch under the skin, they feed on the hornworm from the inside out and it dies. If you see or have a tomato hornworm with these while pills on it, don’t kill it! It will die, and it is also carrying more beneficial wasps to help naturally control hornworms in your garden.
Tomato Hornmorm with Brachoid Wasp Eggs on It’s Back
Organic Insecticide To control Tomato Hornworms
How do you get rid of hornworms without using pesticides? Using insecticides is an option.
When all else fails in your home vegetable garden, insecticides are available. These are a product that is formulated using natural product and are a much safer choice.
Whatever you choose, make sure they have been approved by the OMRI (Organic Material Review Institute). This institute researches and tests products to make sure they are safe for use.
I’ve not had to use any of the so far, but the following is a list that have been labeled and approved to be safe. Be sure to look for the OMRI logo on whatever you choose to use.
This is a biological insecticide that can be used on fruit trees, vegetables, flowers and other plants. It affects only the larva (caterpillar) stage of the caterpillar. Once ingested, the caterpillar dies. It does not affect birds or beneficial insects.
LAWN & GARDEN PRODUCTS P MONTEREY B.T. CONCENTRATE 32 OUNCE
“Safer Brand” Garden Dust
This insecticide will be ingested by the hornworm and it will cease to eat within a couple hours. It will die in a matter of a few days. This will not harm beneficial insects or honeybees.
Safer Brand 5162 Garden Dust Caterpillar Killer with B.T. 8 oz.
Used as pest lure, repellent or trap. This is not one of my favorite though it has been approved. It kills a broad range of more than 40 insects including the hornworm. It takes up to 12 hours to rid the problem.
PyGanic Gardening 8oz, Botanical Insecticide Pyrethrin Concentrate for Organic Gardening
“Safer Brand” Home Spray
Uses naturally occurring bacterium to control and kill caterpillars and other leaf eating plants. Has no effect on earthworms, birds, or other beneficial insects like ladybugs, honeybees and beetles.
Safer Brand 5163 Caterpillar Killer II Concentrate, 16 oz
Monterey Garden Insect Spray
This organic control is probably my favorite because its active ingredient is produced by fermentation. It controls caterpillars, leafminers, borers, fruitflies and more.
Monterey LG6135 Garden Insect Spray with Spinosad Concentrate 32oz
As I mentioned, I have never used any of these, but I have do some pretty extensive research on them. Being a pollinator friendly organic gardener, it is important that you know what you are using on your organic home garden.
I don’t want to be killing beneficial insects or putting harmful chemicals on my garden that my family will be eating.
Prevention of Tomato Hornworms
We’ve talked extensively about control of the tomato hornworm but there are a couple ways of what I’d call prevention too.
Row covers are just what the name says. They cover the row to prevent unwanted moths and insects from getting to the tomato plants.
They do have their time and place to be used, but with this, comes the opposite too. Beneficial insects that you want on your tomato plants, are unable to get to them.
- Green Lacewings
- Ground Beetles
- Brachonid & Trichogramma Wasps
- Damsel Bugs
- Aphid Midges
- Preying Mantis
As a preventitive, this is by far my favorite product. I do feel this is the easiest and safest way to naturally kill hornworms. I would highly recommend this to any home gardener.
Diatomaceous Earth is a completely natural product made of tiny fossilized aquatic organisms. It looks like tiny broken pieces of glass on the soil and as predators crawl across it, their body is cut or scored by the tiny sharp organisms and they die. No toxic poisons are in it at all!
Of course, with this, some beneficial insects may suffer too, but the alternative outweighs not using it.
I know we’ve talked a lot about hornworms. I’m sure now that you understand more about their life cycle and how they feed, you can be better prepared to control and rid your garden of them when they appear.
What natural control most intrigues you and how will you be trying?
More Gardening Tips
- 5 Natural Ways to Control Cabbage Moths
- How to Grow Carrots
- Green Beans, How to Grow , Plant and Harvest
- How to Grow Cabbage
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Dianne Hadorn is the owner of Hidden Springs Homestead nestled in the hills of East Tennessee. She is a Master Gardener and enjoys helping others learn how to grow and preserve their own food and sharing tips for living a more frugal lifestyle.
Anyone that has found hornworms in the vegetable garden knows they can literally destroy a plant in no time. These caterpillars can be a trifling nuisance for tomatoes, peppers, and some herbs.
One hornworm can strip a plant of it’s leaves in just a few hours – they are eating machines. Because of their ferocious appetites, hornworms can grow to a large size in just a few days.
They can reach sizes of 6 inches long and almost an inch in diameter. Hornworms can be very difficult to prevent, but they can be slowed down.
If you have found a hornworm munching on your precious vegetable plants, here are some tips for getting rid of these pesky critters:
Tips for Finding the Hornworms
One of the best practices is to check your plants daily (twice a day is even better) for any signs of hornworms.
Don’t worry – you’ll notice if they are present very quickly. Check for any chewed leaves. Just the “meaty” parts of the leaves will be chewed off, the veins of the leaf will most likely still be present.
Obviously, check to see if you spot the caterpillars themselves. Hornworms can be tough to spot at first because they blend in very well with the plants. Make sure to look closely, and check under the bottom sides of leaves.
Also, look on the ground and on leaves for any signs of hornworm droppings. It will be very noticeable for a large hornworm. It looks similar to tiny rabbit poo – small black or dark brown pellets.
Another way to spot them is to spray the plant with soapy water. The soapy water will cause the hornworms to wiggle and convulse around, making it easier to spot them.
If hornworms are found immediately remove them from the plant and either drop them in a container of soapy water or smoosh them.
One thing to watch for when handling hornworms, when you grab them they will turn around and eject a dark brown or black liquid on your hand.
It’s advised to use gloves or tweezers to pick them up with, unless you want that goop on your hands.
Tips for Organic Hornworm Control
Of course, besides handpicking the hornworms you find, you’ll want to prevent them from getting to your nightshade vegetables in the future.
Here are a few things that will help to control their presence in your vegetable garden:
Take Action Before the Hornworms Emerge
You have probably heard the expression – “A good defense starts with some good offense”, right?
It’s no different when battling a pesky caterpillar that wants to eat up your harvest. Follow these tips when preparing your vegetable garden for planting:
When tilling, or loosening the soil where you grew tomatoes the previous year watch for the pupae of the hornworm in the soil.
They are brown torpedo-shaped, sac-like objects that look sort of like a little tube. Here’s a site with some great pictures of the hornworm pupae.
They can be difficult to catch, but careful cultivation may find a few. Have an extra set of eyeballs with you to hunt for the pupae.
- Rotate the crops in your vegetable garden, and avoid planting tomatoes, or other nightshade vegetables in the same area.
The moths may still fly around and find your tomatoes anyway, but crop rotation will still have its benefits.
Use a black plastic mulch for your nightshade vegetables. By covering the soil with black plastic garden mulch it can help prevent the moth from emerging in spring and laying eggs on your plants.
If the area is covered then the moth can’t emerge and will die.
Use a Homemade Moth Deterrent
You can use a mixture of garlic, insecticidal soap, and cayenne powder diluted with water to keep the sphinx or hawk moth out of your garden and from laying eggs.
This will help to control the hornworms from entering your vegetable garden to begin with.
Put the mixture in a garden sprayer or a bottle sprayer that attaches to a water hose, and spray your plants.
The moths hate the smell of the solution, and will not get near it.
Attract Insectivore Birds to Your Yard
Place a couple bird feeders, or bird baths, around your vegetable garden in strategic locations.
Some birds, including robins and mocking birds, can spot the worms and devour them for lunch.
Plant a Trap Crop
You can also plant a big patch of dill as a trap crop on one end of your vegetable garden.
Hornworms absolutely love dill, and might go for the dill plants instead of the tomatoes or peppers.
Diversions are legal when fighting garden pests.
Attract Parasitic Wasps
Public enemy number one for hornworms are the parasitic wasp. The parasitic wasp lay their eggs on the backs of hornworms, which the caterpillar will carry around until the eggs hatch. Once the wasp eggs hatch, they will kill the hornworm for food.
Use a Pop-up Net
Gardener’s Supply offers a Pop-up Bird Net that surrounds the plants in a moth-free setting.
There are a couple downsides to using the Pop-up Net. One is the cost – if you have a large tomato garden it could get expensive.
Secondly, if there are hornworm pupae in the soil where you place the Pop-up Net you could inadvertently trap the moth in with the tomato plants, giving it free picking on the plants.
So, if you use the Pop-up Nets make sure to cultivate the soil well, and add black plastic mulch on top to keep hornworms at bay.
Use Biological Warfare on Hornworms
I’m not saying you need to buy gasmasks, but you may need to use Bacillus thuringiensis, or Bt.
Bt is an organic pesticide that is completely safe to use on vegetables. Bt is mixed with water then sprayed on the tomato plants. When the hornworm eats a leaf with Bt, the hornworm losses its appetite and dies.
The awesome thing about Bt is it only harms insects that eat the leaves, so beneficial insects and pollinators are not harmed.
Thuricide, commonly called Caterpillar Control, is a good form of Bt to use for hornworms.
Using a Combination Battle Plan
As you can see there are many different ways to defend against hornworms. Unfortunately, it may take several, or maybe even all of them to successfully keep hornworms from devouring your precious tomato plants.
Even with several control methods in place you may still need to observe and handpick hornworms from your plants from time to time.
For more information about hornworms, please visit the Hornworms page.
Tomato Hornworm Prevention
By Michelle Ramsey, Butte County Master Gardener, June 28, 2013
If something is eating your tomato plants or your eggplants, hornworms may very well be the culprit.
Two common species of hornworms seen in the garden are the Tomato Hornworm (Manduca quinquemaculata) and the Tobacco Hornworm (Manduca sexta). They can be differentiated by how many white stripes the larvae have on each side of their bodies. Tobacco hornworm larvae have 7 diagonal stripes on each side, while the tomato hornworm larvae have 8 chevron-shaped stripes. Mature hornworm larvae can be very large, up to 4 inches long (they will most likely be the largest “caterpillar” you’ll see in your garden). Hornworms feed on blossoms, leaves and fruit and are particularly known to cause damage to tomatoes and eggplants. Damage to plants typically occurs in mid-summer (but may also be seen in late summer). In their larval stage, hornworms are green caterpillars often seen hanging upside down on the plants. They have a “horn” at the rear end of their body. In the early summer, hornworm eggs (laid singly on leaves), hatch into larva. The larvae feed on leaves for 3-4 weeks and then burrow into the ground to pupate. The pupa over-winter in the ground and then emerge as adult moths. Adult hornworm moths are strong fliers with a wingspan of up to 5 inches.
The larval form of the hornworm is the only stage that causes damage to your plants. Hornworms can be hard to find as their green coloring provides a nice camouflage for them amidst the tomato plant leaves. Foliage damage (and possibly some damage or scarring of fruit) and large droppings on the dirt under the plants are indications that hornworms are present in the garden. When the plant is shaken gently hornworms will sometimes make a clicking sound which can help you locate the intruder. Natural enemies of hornworms are the Trichogramma parasitic wasp which lays eggs in the hornworm eggs and the Hyposoter exiguae parasitic wasp which infests the hornworm larvae as a parasite.
The most common methods of hornworm management are hand-picking them off plants and/or snipping them with shears. However, if the hornworm infestation is out of control, an organic spray (Bacillus thuringiensis or Spinosad) may be applied. These sprays are effective against smaller hornworm larvae but will not destroy the natural enemies of the hornworms. Crop rotation and disking (breaking up and turning over the soil) after harvest destroys pupae in the soil, and will help prevent emergence and a repeat of the hornworm life cycle in your garden the following year.
For additional information visit:
06 Aug Tomato Hornworms
Methods of Control
Easy to control by handpicking, daily observation is key. Normally found in small numbers, even one or two can strip a plant in just a day. Simply squash or drop them in soapy water. Rototill your garden beds in late fall, after the harvest, to kill overwintering caterpillars and pupae.
See also: The Colorful World of Cherry Tomatoes
The essential oils in the marigold act as a repellent to many insects, including the moth that lays the tomato hornworm. Plant marigolds around crops that attract tomato hornworms, as well as throughout the garden.
Beneficial insects are the most effective means of keeping tomato hornworms in check. Hornworm caterpillars are a favorite host for parasitic wasps. The wasp lays it eggs in the caterpillar. When the larvae hatch, they consume their host from the inside out, leaving behind only mummified remains. Attract these beneficial insects by planting a wide variety of herbs and open-pollinated flowers. Try plants with an umbrella or flat shaped clusters of tiny flowers like Queen Anne’s lace or yarrow. Angelica, coriander, cosmos, and tansy also support parasitic wasp populations.
A Final Note
Consider planting more than you need so that the loss of a few plants is not an issue. Allow some of these creatures to survive and pupate. The tomato hornworm emerges from its cocoon a five-spotted hawk moth, also referred to as a ‘hummingbird moth’. This large-bodied, pale brown or gray moth resembles a hummingbird in its body shape and behavior. The five-spotted hawkmoth becomes active after dusk, appearing like a ghostly hummingbird as it hovers around moonflowers and ginger lilies, drinking nectar.
See also: Butterflies – Flying Flowers
Tomato Hornworm – Organic Control Of Hornworms
You may have walked out to your garden today and asked, “What are the big green caterpillars eating my tomato plants?!?!” These odd caterpillars are tomato hornworms (also known as tobacco hornworms). These tomato caterpillars can do significant damage to your tomato plants and fruit if not controlled early and quickly. Keep reading to learn more about how you can kill tomato hornworms.
Identifying Tomato Hornworms
Image by Beverly NashTomato hornworms are easy to identify. They are bright green caterpillar with white stripes and a black horn coming off the end of these tomato caterpillars. Occasionally, the tomato hornworm will be black instead of green. They are the larval stage of the hummingbird moth.
Normally, when one tomato hornworm caterpillar is found, others will be in the area as well. Examine your tomato plants carefully for others once you have identified one on your plants.
Tomato Hornworm – Organic Controls to Keep Them Out of Your Garden
The most effective organic control for these green caterpillars on tomatoes is to simply hand pick them. They are a larger caterpillar and easy to spot on the vine. Hand picking and placing them in a bucket of water is an effective way for how to kill tomato hornworms.
You can also use natural predators to control tomato hornworms. Ladybugs and green lacewings are the most common natural predators that you can purchase. Common wasps are also vigorous predators of tomato hornworms.
These tomato caterpillars are also prey to braconid wasps. These tiny wasps lay their eggs on the tomato hornworms and the larva literally eat the caterpillar from the inside out. When the wasp larva becomes a pupa, the hornworm caterpillar becomes covered with white sacks. If you find a tomato hornworm in your garden that has these white sacks, leave the tomato hornworm caterpillar in the garden. The wasps will mature and the hornworm will die. The mature wasps will create more wasps and kill more hornworms.
Finding these green caterpillars on tomatoes in your garden is frustrating, but they are easily taken care of with a little extra effort.
How to Get Rid of Tomato Hornworms in Your Garden
If your vegetable garden includes tomato plants, there’s a good chance that it will attract the attention of the pesky tomato worm, or hornworm, at some point. A greenish caterpillar with a spike or horn on its tail, tomato worms can be found in just about every region of the United States, and they can wipe out your plants in no time at all.
Have your ever noticed small holes in the leaves, fruit and stems of tomatoes, peppers and eggplants? Are small brown droppings present on your garden plants? If so, you may be observing the presence of the tomato hornworm.
However, as frustrating as an infestation can be, there are a number of steps you can take to control and eliminate hornworms in your garden. We’ve prepared this guide on hornworms and their life cycle to help you learn how to get rid of them. With a little hard work and the careful use of insect-killing products approved for organic gardening along with the use of beneficial insects, you can repel and prevent the tomato hornworm from eating your precious fruit before you do.
Thwarting a Tomato Caterpillar Invasion
Eliminating this pesky insect can be difficult. However, there are various simple tomato hornworm control techniques that can help you tackle your caterpillar problem.
Your first step should include thoroughly tilling soil at the beginning and end of the gardening season to destroy the larvae. Use a root-tiller, especially during the nongrowing season. Larvae are quite large and spend their winters buried just below the surface while in their pupal stage. A good tilling will break up the pupas and prevent them from emerging next summer.
There are also a number of beneficial insects that eat hornworms while avoiding your plants. Braconid wasps, ladybugs and lacewings either destroy or feed on the eggs of hornworms, helping to control the population. Make sure to release these beneficial insects before the infestation is full-blown, since they are better for preventing a population from growing than destroying one that already exists.
However, sometimes the best approach is more hands-on. Especially if your garden is small, you can pick the tomato worms out of the soil by hand; they are completely harmless and won’t bite or sting. They are large and easy to grab. Just drop them into a pail of soapy water to destroy them. Because of their green color, they can easily blend in when sitting on a stem or a leaf. If you are having trouble finding them, just spray the area with water, and the caterpillars with begin to squirm.
The Best Form of Tomato Worm Control
While there are several steps you can take before turning to insect-killing products, sometimes doing so is the wisest choice, especially if the size of your garden makes manual removal inefficient. A product such as Safer® Brand Garden Dust can quickly and easily be used for tomato hornworm control. The active ingredient in Safer® Brand Garden Dust is bacillus thuringiensis, a naturally occurring substance that causes the worm to stop feeding in a matter of hours when ingested. The tomato caterpillar typically dies in just a few days.
Safer® Brand Garden Dust is an OMRI® Listed product, meaning it contains ingredients that are approved for use in organic gardening practices.
For best results in controlling tomato worms, thoroughly cover plant leaves with the product and reapply every seven to 10 days or as often as necessary. Since caterpillars don’t hatch all at once, you can destroy an entire infestation only to find that they have reappeared in a week or so. Just apply 2 to 3 ounces for every 50 feet of garden every time caterpillars appear.
What Is a Tomato Hornworm?
The tomato hornworm caterpillar, or manduca quinquemaculata, is a greenish caterpillar measuring about 4 ½ inches long. It has a spike or horn on its tail, giving this insect pest its name. It can be found throughout North America and has long wreaked havoc on tomato, pepper, tobacco, potato and eggplant crops. They especially love eating leaves and stems, although they will sometimes feed on the fruit of plants as well.
Even though they are large, they are also the color of the leaves they feed upon, providing them with excellent camouflage. White stripes can be found across their bodies, finishing with their signature red horn at the end.
Eventually, these caterpillars become moths, called the hawk or sphinx moth, which are brown or gray with white zigzags across their wings. The larval stage of the tomato hornworm is the only destructive stage since it feeds on the leaves, fruit and stems of plants.
Keep in mind that if the moths are present, they will lay eggs which will eventually grow into plant-hungry larvae. So if you see this insect in any of its three stages, you should consider taking appropriate steps for controlling the population.
In addition to tomato hornworms, tobacco hornworms are also often found in North American gardens. The tobacco hornworm, a relative of the tomato hornworm, is found on tobacco plants throughout North America. Since this larvae has similar eating habits, the control methods are also much the same.
Tomato Hornworm Life Cycle
Adult moths will mate and lay eggs in late spring. Their eggs are small, green spheres, and can usually be found on the undersides of the same leaves they will someday eat. The eggs hatch in about six to eight days. After that, the larvae will go through development in stages that last up to four weeks, which includes the ravenous feeding that can cause such destruction within your garden.
After a summer of getting their fill, they will go below ground to spend the winter in the pupal stage, emerging in June or July of the following year as adult tomato hornworm moths, ready to begin the cycle over again.
This is why you need to interrupt the tomato hornworm life cycle one way or another. Whether you destroy the pupas with a root-tiller or kill the larvae with an insect-killing product, by interrupting the cycle, you will prevent future infestations of hornworms.
Tomato Hornworms’ Habitat
Tomato hornworms can be found on tomatoes, peppers, eggplants and other members of the nightshade family. In other words, if you live anywhere in North America where you can plant a vegetable garden, you run the risk of hosting hornworms.
In fact, hornworms need gardens, with their broad leaves and soft soil, in order to survive. Because they lay their eggs, feed and breed around vegetable plants, they are just as tenacious in protecting their claim to your garden as you are about eliminating them.
This is what makes them so difficult to eliminate. They aren’t going to be discouraged and look for greener pastures elsewhere. If only a handful remain, they will quickly breed and return to their previous numbers.
Considering how inviting your garden or field is to these pests, you have to do everything you can to eliminate the entire population before they eliminate your hard work.
Symptoms of Tomato Hornworm Damage
Holes in the leaves, fruit and stems of tomatoes, peppers and eggplants are typically the first thing you’ll notice in your garden, and this likely indicates the presence of the tomato hornworm. A few holes in your plants may not seem like a big deal, but if this minor damage is allowed to progress, it will soon destroy your plants and ruin your crop.
With its large size, the tomato hornworm might be visible on plants. In fact, the first time you see one of these large insects, it can be quite shocking. Obviously, if you find a caterpillar on your plants, you know the hornworm is the culprit. However, its coloring does camouflage it very well, so it can often go unnoticed despite its size.
If you find the telltale holes but are still unsure if you have a true hornworm infestation, the next step is to look for hornworm droppings. Clustered tan or brown droppings may be seen on plant leaves and parts. Often you can find a resting hornworm right above where you find their waste.
Once you find proof of hornworm damage, you can be confident that you are hosting an entire hornworm party. If there is one larvae or one patch of droppings, eggs and other larvae are sure to be in the garden as well. If you see symptoms, it’s time to start treating your garden or fields for hornworm infestation.
Results of Tomato Hornworm Infestation
Hornworms are voracious eaters. If left undisturbed on a plant, hornworms can completely defoliate your garden vegetables in just a few days. With the larvae eating the leaves and new stems of plantings, the planting may die, although plants can typically recover if the hornworms are removed early.
However, even if the plant survives the initial leaf feast, if you don’t remove the larvae, they will move on to other, more prized fruits of your garden. Later in the season, the tomato hornworm feasts on the actual tomatoes, peppers and eggplants, making your fruit or vegetables unmarketable and unappetizing.
If you’re farming with the goal of making money, a hornworm infestation can hit your pocket hard. Even if you have a small garden, hornworms can erase hours of work and spoil the joys of a homegrown vegetable on your family table.
How to get rid of Tomato Hornworms
As we already discussed, there are a number of insect-control products that can assist you in your quest of taking back your garden from hornworm invaders.
With so many products on the market, it is tempting to purchase the first one you see on the shelf in your local garden center. However, not all products are created equal. Chemicals have a lasting impact on the environment, so you should know what’s in your insect control products and how they work.
With that in mind, here is a quick rundown on a few organic and effective options.
What OMRI® Compliant Gardening Products Are Out There?
Products such as Safer® Brand Garden Dust, Safer® Brand Tomato & Vegetable Insect Killer and Safer® Brand Caterpillar Killer II with B.T. Concentrate are approved for organic gardening and can be used for effective tomato hornworm control.
Safer® Brand Garden Dust provides an effective method of eliminating tomato hornworms in your garden or field without environmental concerns or potential harm to wildlife and beneficial insects when used as directed.
Insecticides containing B.T., such as Safer® Brand Caterpillar Killer II with B.T. Concentrate, can also be an effective method of controlling the hornworm.
How Do These Products Work to Control Tomato Hornworms?
Safer® Brand Garden Dust kills hornworm larvae, thereby preventing further damage. When the worm ingests the B.T., it works as a gut rot poison that makes the worm stop feeding. The tomato hornworm will stop feeding immediately and die within days from malnutrition.
Safer® Brand Caterpillar Killer II with B.T works in much the same way. When a hornworm eats the treated foliage, it will immediately stop eating and die shortly thereafter.
B.T. usually comes in a dust or concentrate and kills a variety of caterpillars and worms, including the destructive hornworm.
Sprays containing pyrethrin such as Safer® Brand Tomato and Vegetable Insect Killer paralyze the insects, resulting in their death. Since they are OMRI® Listed, you know the ingredients are approved for use in organic gardening.
As with any insect-control product, it is recommended with any pesticide to test plants for sensitivity to the product. Spray a small section of the plant in an inconspicuous area and wait 24 hours before full coverage.
Safer® Brand offers a variety of tomato hornworm control products to help control and eliminate this garden pest and revive your plants. Please check out our tomato hornworm-control products for more details, including their chemical contents.
When Should I Use These Products?
As with any gardening product, when you apply affects how well they work. With that in mind, here is a quick rundown on when to use insect-control products so that you can quickly get your hornworm infestation under control.
Any product with B.T. is best applied when it is a cooler time of day, preferably later in the afternoon or early in the evening, since the product breaks down in sunlight and heat. A cloudy day is also a perfect time to apply the product.
When applying pyrethrins to infected plants, do not spray plants in the peak of the day or when temperatures exceed 90° F.
As with any product, carefully read and follow all directions on the product labeling for safe and effective application.
Why Choose a Pest Solution?
Thankfully, many people are starting to realize that products that are compliant for use in organic production are the best solutions available. Why exactly are these products preferred? These solutions break down quickly into their natural elements. They are preferable to chemical pesticides that leave residuals where they are sprayed, causing long-term detrimental effects on the environment.
Plus, if you’re using the wrong insect-control products on produce, these chemicals can make their way into your food, eventually reaching your home and family. You put your love and sweat into your garden because you want to put great food on the tables of your family and whoever else eats your produce. So you want to choose a product that befits the fruits of your labor.
Natural Predators of the Tomato Hornworm
In addition to natural products, natural predators and beneficial insects can effectively control the hornworm population in your garden or fields. How do these predators work and how can you be sure they aren’t just as harmful as the caterpillars you are trying to kill? Here is a quick rundown on natural beneficial insects that you can employ to keep your garden pest-free.
What Insects Are Beneficial?
Parasitic braconid and trichogramma wasps, ladybugs and green lacewings are beneficial insects that help to control tomato hornworm problems. They can be attracted naturally to your cornfield or garden area where your vegetables are planted, and there are some companies that raise these insects and sell them to consumers.
How Do These Insects Work?
Different beneficial insects work in different ways. On the one hand, the parasitic wasp lays its eggs inside the tomato hornworm’s egg, destroying the hornworm egg in the process. The presence of parasitic wasps have shown success rates of more than 50 percent in eliminating hornworm populations.
On the other hand, upon hatching, the green lacewing larvae will eat the larvae of the tomato hornworm. They eat hornworms and their eggs just as voraciously as hornworms eat your plants. Ladybugs feed much the same way.
Either way, whether they are eating or destroying hornworm eggs, the presence of beneficial insects will help interrupt the life cycle of the hornworm and destroy the population.
How Do I Get Beneficial Insects Into My Garden?
There are a number of ways to invite these beneficial insects into your garden. Planting pollen and nectar-bearing flora near the tomatoes and peppers may attract these beneficial predators. If trying to attract them doesn’t work, they can also be purchased from companies who raise them. These are the types of bugs you will be glad to see while you are gardening, as they work hard to keep your plants hornworm free.
When Should I Employ These Insects?
Plant the pollen or nectar-producing flora as soon as possible according to the temperature of your area. Most local greenhouses and garden centers can help you determine the right planting time.
If you are purchasing insects, there are a few basic guidelines for their release. Ladybugs should be released in the evening. Lacewing larvae should be spread immediately after you have acquired them. Wasps should be released when you observe the presence of adult hornworm moths.
For more specific instructions, contact a company that raises beneficial insects to find out when they should be purchased and released for maximum hornworm control.
Why Should I Use a Natural Predator?
There is no more natural of an approach to hornworm control than employing a natural predator. These insects normally feed on hornworms without human intervention. By introducing them into your garden, you are helping Mother Nature do something she would do normally. They don’t contain any chemicals and are a healthy part of the ecosystem. Beneficial insects are an effective and guilt-free solution to your hornworm infestation.
The tomato hornworm and its cousin the tobacco hornworm are pests that are as destructive as they are annoying. In a matter of days, these moth larvae can completely destroy a plant, undermining the hours of work that you’ve put into your garden or field. With their camouflaging color, they can often go undetected. However, if you can learn to recognize the signs – such as holes in the leaves of your plants or the sight of brown droppings on your foliage – you can begin to take the proper steps to take back your garden.
Tilling the soil and manually removing hornworms can destroy the life cycle of these pests, especially if you have a small garden where working with your hands is more manageable.
If you need a little more power, natural products are an effective solution for killing and eliminating the threat to your produce.
Hopefully this guide on how to get rid of tomato hornworms has helped you identify the damage these caterpillars cause and the best ways to address the problem. With these approaches, your garden will quickly recover from the damage caused by your unwanted guests.
Safer® Brand leads the alternative lawn and garden products industry, offering many solutions that are compliant with organic gardening standards. Safer® Brand recognizes this growing demand by consumers and offers a wide variety of products for lawns, gardens, landscapes, flowers, houseplants, insects and more!
How to protect your plants from tomato hornworms
Check plants for tomato hornworms at least twice per week during the summer.
Remove weeds regularly
- Remove weeds to reduce the number of sites where worms can lay eggs.
- Till the soil after harvest to destroy burrowing caterpillars and pupae.
Pick hornworms off plants
- This is the most effective means of managing them.
- Tomato hornworms are easy to find because of their large size.
- Drop them into soapy water to kill them.
Natural enemies can control hornworms
There are many natural enemies of the tomato hornworm.
- General predatory insects such as lady beetles and green lacewings often prey upon the egg stage and on young caterpillars.
- Another important predator is the paper wasp, Polistes spp. This common wasp feeds on many types of caterpillars including those found in gardens.
Tomato hornworms are also parasitized by a number of insects.
- One of the most common is a small braconid wasp, Cotesia congregatus.
- Larvae hatching from wasp eggs are laid on the hornworm.
- The wasp larvae feed on the inside of the hornworm until the wasp is ready to pupate.
- The cocoons look like white rice protruding from the hornworm’s body.
- If you see this happening, leave the hornworms in the garden to allow the adult wasps to emerge.
- These wasps kill the hornworms when they emerge from the cocoons.
- Then the wasps look for other hornworms to parasitize.
Pesticides are generally not necessary. But, if other options are not effective or practical, you may consider applying a product.
It is easier to control small caterpillars than large ones. Treat tomato hornworms before defoliation is severe.
Some pesticides that can be used for tomato hornworm treatment:
- Insecticidal soap
- Bacillus thuringiensis subsp. kurstaki
CAUTION: Mention of a pesticide or use of a pesticide label is for educational purposes only. Always follow the pesticide label directions attached to the pesticide container you are using. Remember, the label is the law.
Be sure that the fruit or vegetable you wish to treat is listed on the label of the pesticide you intend to use. Also be sure to observe the number of days between pesticide application and when you can harvest your crop.
Tomato worms or tomato hornworm Manduca quinquemaculata is a very common green caterpillar in North America.
This tomato caterpillar eats a wide variety of popular veggie host plants including members of the Hemlock family, such as:
- Tomato plants
The tobacco hornworms Manduca sexta wreak havoc on tobacco crops. These enormous and rather dazzling-looking tobacco worm caterpillars are relentlessly destructive.
They eat leaves whole and also cause massive damage to stems, fruits and plants as a whole.
Our Top Picks On How To Get Rid Of Tomato Worms
- Bacillus thuringiensis bt
- Food Grade Diatomaceous Earth
- Neem Oil – online at Amazon
- Insecticidal soap
Tomato hornworms share some characteristics with the tobacco hornworms.
Even though they are large and flashy looking, they can hide with ease in the vegetable garden because their coloring and markings tend to blend in with the crops and plants they pillage.
For this reason, you may find yourself surprised by areas of mass destruction of a big green caterpillar without ever having seen one of these little devils at work.
You are most likely to find this damage beginning in midsummer, and if you don’t put a stop to it, the tomato horn worm can ruin your entire growing season and your crops.
In this article, we will provide sound advice for identifying and dealing with these green worms on tomato plants early and efficiently. Read on to learn more.
What Do Tomato Hornworms Look Like?
Tomato hornworms (aka: Manduca quinquemaculata the Five-spotted Hawk moth) are quite large. The five-spotted hawkmoths also measure between three and six inches long, and they are quite sporty with a bright green body, seven white stripes running diagonally and a prominent red or black horn at the rear end.
The parent moths are also quite large with a wingspan of four or five inches. The moths are brown or gray with zig-zagging white markings on the wings and brown or orange spots on their heavy bodies.
You may have heard these moths referred to as Hawk Moths or Sphinx Moths. They are rather impressive because they can fly very fast, and they can hover like hummingbirds. Sometimes they are called hummingbird moths because of this.
The Tomato Worms Life Cycle
Where do tomato worms come from? The pupae overwinter in the soil. At this stage, they are dark brown.
In the late spring, adult moths emerge from the soil and mate. Then they lay their eggs, which are green and spherical, on the underside of leaf of their chosen plant.
The tomato hornworm eggs hatch from the leaves within five days and the larvae begin their above-ground life cycle. This is a multi-stage process that is completed within a month.
At the end of the month, they burrow beneath the soil and become larvae. This stage lasts for two-to-four weeks. At the end of the larval stage, adults emerge to mate and lay eggs.
This cycle is completed twice annually, so you will see new adults emerging from your garden in late spring and again in the mid-summer.
How Can You Find These Large Tomato Caterpillars?
If you notice Sphinx Moths around your garden or your porch light at night, you should begin looking for their eggs and small caterpillars amongst your crops.
Look at every tomato leaf if you can. Catching them early is key to control.
Signs of a tomato hornworm caterpillar garden infestation include black caterpillar droppings (frass) on the ground around your plants and the leaves.
How To Get Rid Of Tomato Hornworms And Its Caterpillars?
A single green horned tomato worm can consume all of a plant’s leaves in a very short period of time. This large green caterpillar has a voracious appetite and eats constantly, so they grow very large very quickly. It is possible for them to grow as large as six inches in length and one inch in girth.
Follow these tips to eradicate hornworms from your garden:
1. Check your plants every day for signs of these pests. These signs include:
- Chewed leaves
What do caterpillars eat? Note that when green tomato worms eat leaves, they usually leave the veins and only eat the flesh of the leaf. When you see this, you can be sure you are dealing with hornworms.
2. Be thorough! Scan both sides of leaves and look around on the ground for signs of worms on tomato plants. Be aware that hornworm poop is quite large. In fact, you may even mistake them for rabbit droppings.
3. At the early stage, you can just give the foliage a good, vigorous spraying with plain water to knock small caterpillars off and drown them. This goes a long way toward solving your problem.
4. In addition to a visual inspection and spraying with water, try spraying your plants with a solution of dish soap and water. This spray mixture causes the caterpillars quite a bit of distress. They’ll move around trying to get away, and you will be able to see them and catch them. Just drop them into a bucket of soapy water to finish the job.
TIP: Wear gloves when picking off hornworms by hand because they will attempt to defend themselves by spitting “tobacco juice” (dark brown liquid) onto your hand.
9 Ways To Practice Prevention
You can prevent tomato worms from returning to your garden by taking a few simple precautions.
1. When you till up your garden soil, keep an eye out for hornworm larvae. They look like small, brown torpedoes. Pick them out and drop them in a bucket of soapy water.
2. Don’t plant the same crops in the same place year after year. Crop rotation helps keep all pests off guard. Never plant any type of nightshade varieties in the same place from one year to the next. For example, when you rotate your tomato plant crops (for example) you should not replace them with potatoes or another type of nightshade.
3. Cover the ground around your tomatoes in the nightshade family with sheet of black plastic mulch. The plastic helps block the emergence of the adults from the soil in the late spring.
4. Spray your garden with a natural mixture of water, cayenne powder, insecticidal soap and garlic to prevent Sphinx Moths from laying eggs on your plants.
Diatomaceous Earth: Its Benefits And How To Use It In Your Garden – is also a good pest control option for not only caterpillars but also:
- Beetles – Flour, Darkling, Grain, Carpet and Colorado Potato beetles
- Earwigs (pincher bugs)
- Centipedes, Millipedes, Sowbugs and Pillbugs
- Slimy slugs and snails
5. Make your yard a haven for caterpillar eating birds. Be sure to set up bird baths and feeders in your yard and garden to enlist the help of these natural predators. Mockingbirds, Robins and other larger, carnivorous and omnivorous birds are very fond of big juicy hornworms.
6. Decoy hornworms with a trap crop. Planting a crop of dill may help keep hornworms off your hemlock crops. They prefer this plant, and having them gathered around it will make it easier for you to find them and eliminate them.
7. Encourage the presence of parasitic wasps a natural enemy. These wasps lay eggs on hornworms’ backs. When the eggs hatch, the wasp larvae eat the hornworms.
8. Place pop-up bird netting around individual plants. It is supposed to keep birds away from your fruit, but hornworms are so big that they cannot get through the mesh either. This solution is a bit cumbersome because these nets are rather expensive. Also, they do nothing to prevent pupae emerging from the soil in the form of tomato hornworm moths.
9. Make wise use of Bacillus thuringiensis bt. This organic pesticide consists of a form of bacteria that is very effective in poisoning young caterpillars but has no effect on other garden fauna. The strain of Bt that is known as Thuricide is an excellent choice for controlling hornworms.
You simply mix the liquid or powdered concentrate with water and spray your tomato plants with it early on to catch hornworm caterpillars before they can do much damage.
Because this solution is caterpillar-specific, remember that it will also kill butterfly caterpillars, so apply it carefully and keep it away from your butterfly garden and individual plants that butterfly caterpillars enjoy.
10. Attract beneficial insects. In addition to predator braconid wasps, a number of other beneficial insects lay waste to hornworms by eating the eggs. Be sure to protect and encourage lady-bugs and lacewings, as well as trichogramma wasps.
Related Reading: How To Kill Wasps Naturally
Vary Your Pest Control Methods
It is important to use a wide variety of ways to control and eliminate hornworms because they can build up resistance and learn workarounds for just about anything you do if you only do one thing. Keep them on their toes by varying your methods throughout the growing season.
A good technique is to use bt Bacillus thuringiensis early on. Give it 48 hours to dissipate and then introduce predatory insects to your garden to keep your hornworm numbers low. At the end of the growing season, be sure to till your garden.
This disrupts the soil and interferes with the pupae underground. Some studies show that tilling can kill as much as 90% of buried larvae. As mentioned, if you see hornworm pupae when you till, be sure to collect and destroy it.
When you see hornworms with parasitic wasp cocoons on board, collect them and keep them in an area of discarded or volunteer hemlock crops or dill. Allow the wasps to hatch and eat the hosts. Then you will have a beautiful, healthy crop of predator wasps to continue helping you year after year.
Take care of your tomatoes and other crops by making use of the above tips to any control caterpillar on tomato plants. Make your garden and soil free from the danger of tomato pest and tomato hornworm damage for a more productive harvest.
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PHOTO: Brad Smith/Flickr by Leslie J. Wyatt July 28, 2014
Something is eating your tomato plants, stripping leaves until only stems remain. You find “frass” (larval droppings) on neighboring leaves and on the ground. The culprit? It’s 4 inches long, green as grass, sporting eight V-shaped white marks down each side and a blue-black “horn” on one end: the tomato hornworm, the larval stage of the sphinx moth, also known as a hummingbird or hawk moth.
Tomato hornworms (Manduca quinquemaculata)—and their orange-horned cousin the tobacco hornworm (Manduca sexta)—can strip leaves and blooms in record time and munch on fruits, as well. These big babies feed only on solanaceous plants, aka the nightshade family. Although tomatoes are their main target, peppers, eggplants, potatoes, and related weeds, such as henbane, jimson weed and nightshade, can also fall prey to them. The horns of these pests intimidate predators, but aren’t dangerous.
Hornworms can produce between two and four generations per growing season, depending on the region. Two to eight days after the moth deposits her spherical, greenish-white eggs primarily on the lower surface of foliage, 1/2-inch-long larvae hatch out. For approximately the next 20 days, your garden is at risk of their voracious appetites.
Here are six ways you can keep tomato hornworms from decimating your garden.
First line of defense is tilling—spring, fall and every few weeks in between. The University of Florida says the average life cycle of the hornworm is 30 to 50 days, unless the pupae enter diapause (dormancy). Mature larvae drop to the ground, burrowing to a depth of roughly 1/2 inch, and then enter the pupae stage.
- Advantage: destroys up to 90-percent of the 45-60mm pupae, thus effective in population control
- Disadvantage: doesn’t prevent larvae damage
2. Hand Picking
Unlike many garden pests, a tomato hornworm’s size makes it possible to go on a search-and-destroy mission. The Colorado State Extension office advises that larvae are more easily seen during shadier periods near dusk and dawn, when they tend to feed on the exterior parts of plants.
- Advantage: prevents larvae from defoliating your plants and from reproducing
- Cryptic coloration makes hornworms hard to locate.
- Destroying the caterpillars is distasteful to some gardeners.
3. Light Traps
According to the University of Florida, light traps for adult moths can be used in the garden for added prevention. The moths are attracted to the light and then captured, preventing them from laying eggs.
- Advantage: reduces the egg-laying population
- Disadvantage: minimally effective
4. Predators and Parasites
Lady beetles and green lacewings prey on hornworm eggs and early larval stages, and Japanese paper wasps (Polistes spp.) will attack and feed on all sizes of hornworm larvae. Encouraging wasp colonies near your garden may protect your tomatoes.
Several small parasitic wasps—Trichogramma spp, Cotesia congregata and Hyposoter exigua—will lay eggs and pupate on hornworms. If you capture a caterpillar with what looks like rice grains on its back, sequester it in a screen-lidded container with a few leaves. As the wasps emerge from their little white cocoons, they kill their host and escape the jar, seeking out other hornworms to parasitize.
To increase effectiveness, purchase additional beneficial insects and/or plant host plants.
- Advantage: effective, natural, no-hassle pest control
- Lacewings and lady beetles aren’t effective as the caterpillars gain size.
- With parasitic wasps, a certain amount of defoliation still takes place until parasitism takes effect.
- Paper wasps sting people.
5. Bacterial Insecticides
Bacterial insecticides include Bacillus thuringiensis of the Kurstaki strain (BtK—e.g. Dipel, Thuricide). Applied to foliage, they are most effective when hornworm larvae are small. Caterpillars lose the ability to feed soon after munching leaves sprayed with BtK, according to Gardens Alive, a retailer of eco-friendly garden products. (Follow label instructions for application.) If hornworms have been a problem in previous years, you can spray prophylactically every two weeks to prevent damage to plants.
- You don’t have to find the caterpillars—just spray the host plants well.
- BtK is effective against all caterpillars, but will not harm beneficial insects.
- Disadvantages: Overspray onto butterfly host plants can kill butterfly caterpillars.
6. Chemical Insecticides
Chemical insecticides, carbaryl, permethrin, bifenthrin, and spinosad, kill larvae on contact, though should be used with caution if you have animals near the garden or are concerned about keeping beneficial insect populations intact.
- effective on all stages of hornworms
- readily available
- kills beneficial insects
- toxic to mammals
How to Control and Prevent Hornworms
Tomato and tobacco hornworms are both immature, larval stages of large moths. The damage these worms cause in your garden is the same, but the worms have different markings. Tomato hornworms have a black horn on their rear with white, V-shaped marks pointing forward along their bright green sides. Tobacco hornworms have a red horn on their posterior and diagonal white stripes along their sides.
The adult forms of these hornworms are known regionally as sphinx moths, hawk moths or hummingbird moths. These large moths emerge in late spring and lay their eggs at night on plant leaves. They prefer tomato and tobacco leaves, but they’ll use related plants, too. Under optimal conditions, a single adult female moth can produce up to 2,000 eggs.1 Hornworms hatch in less than one week, and then dine relentlessly on your veggies for up to one month.2 With a life cycle of just 30 to 50 days, two or more generations per season are common.3
Eliminating Hornworm Problems
Handpicking hornworms and drowning them is an effective way to fight these pests. That is, if you can find them while your plants are still standing — and you don’t mind spending time in dark gardens thinking about 2,000 4-inch worms. Fortunately, GardenTech® Sevin® brand insecticides easily control hornworms.
Sevin® Insect Killer Ready to Use and its easy-to-use sprayer make it simple to treat specific plants and pests with a targeted spray. For larger treatment areas, Sevin® Insect Killer Concentrate is perfect for use with pump sprayers. Sevin® Insect Killer Ready to Spray, for hose-end spraying with a regular garden hose, provides the same highly effective control against hornworms and more than 500 insect pests.
These products are known as “nonsystemic” insecticides. This means they don’t penetrate vegetables or plant tissues. Instead, they stay on the surface and kill hornworms by contact. You can treat tomatoes and many other garden favorites right up to one day before harvest. Just follow label directions and guidelines for intervals between application and your harvest day.
Fighting Future Invasions
Hornworms overwinter in the soil in a pupae stage before becoming spring moths that start the season’s hornworm troubles by laying eggs. Tilling your garden after your harvest and again in early spring can kill 90 percent or more of the overwintering pests and reduce hornworm problems for the coming year.3