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Controlling tomato hornworms naturally can be a bit of a battle. But it’s definitely possible. I don’t use any chemicals in my growing space, and I successfully fend off tomato hornworms and other pests using a combination of natural methods.
If you’ve ever grown tomatoes, chances are you’ve encountered the dreaded tomato hornworm that wreaks havoc on your tomato plants. These large green caterpillars can quickly defoliate your plants and ruin your tomato harvest. The tomato hornworm also attacks other members of the nightshade family, like pepper plants and eggplant.
We grow organically, so chemical eradication is out of the question for us. I don’t want to kill off beneficial insects, contaminate my soil and therefore my veg, and add pollutants to the groundwater. So I’m sharing with you my tried and tested methods for controlling your tomato hornworm problem naturally.
Where Do Tomato Hornworms Come From?
Tomato hornworms, scientifically known as Manduca quinquemaculata, are the voracious larvae of the sphinx moth or the five-spotted hawkmoth. They’re native to North America and growers spend a lot of time trying to figure out how to get rid of tomato hornworms from late spring to early fall.
The life cycle of tomato hornworms begins when adult sphinx moths lay their round, greenish-white eggs on the underside of tomato leaves, usually at night. These eggs are often laid singly, which makes them harder to detect. Within a week, the eggs hatch into small green caterpillars with a distinctive horn-like projection on their rear end.
As the caterpillars grow, they go through a series of molts, called instars. Each instar is larger and hungrier than the one before, and by the time they reach their final instar, these caterpillars can be up to four inches long. Throughout their larval stage, tomato hornworms feed voraciously on tomato leaves, stems, and fruits, which can result in significant damage to your plants.
After around four weeks of gorging themselves, the fully-grown caterpillars drop from the plants and burrow into the soil to pupate. They overwinter as dark brown pupae in the soil, emerging as adult moths the following spring to begin the cycle again. Hence why, as you’ll see below, I strongly recommend tilling in fall and again in spring.
Do Tomato Hornworms Eat Tomatoes?
Yes, tomato hornworms primarily feed on tomato plants and can quickly defoliate them if left unchecked. They prefer young leaves but will also eat stems and fruit.
Do Tomato Hornworms Eat Anything Else?
While tomato plants are their preferred food source, tomato hornworms will also feed on other members of the nightshade family, including peppers and eggplants. If you’re growing peppers and tomatoes, it’s a good idea to grow them in different spots in your garden so, hopefully, the moths will only target one set of plants to lay their eggs. But still, be vigilant.
How to Get Rid of Tomato Hornworms Without Pesticides
Tomato hornworms are one of the most destructive pests that can attack your tomato plants. These large caterpillars can strip a plant of its leaves and fruits in just a few days. If you’re an organic gardener, like me, you’ll want to avoid using chemical pesticides to get rid of them. Here are the methods I use to get rid of the tomato hornworm and other common tomato pests, like grasshoppers.
RELATED POST: Do Grasshoppers Eat Tomato Plants?
Companion Planting
Companion planting is a natural and effective way to control pests in your garden. And I plan for companion planting every year when I’m planning what I’m growing where. It’s by far my favorite method for pest control, soil health, and plant health.
By planting herbs like basil or marigolds near your tomato plants, you can create a natural barrier that repels many insect pests, including tomato hornworms.
Basil is particularly effective at repelling the tomato hornworm. Its strong scent confuses the caterpillars and makes it difficult for them to find their host plants. Planting basil in close proximity to your tomatoes can help deter these, and other pests from feeding on your tomatoes.
Marigolds are another excellent companion plant for deterring tomato hornworms. Their bright flowers contain compounds that repel many insect pests, including aphids and whiteflies, as well as tomato hornworms.
In addition to their pest-repelling properties, both basil and marigolds are easy to grow and add beauty and fragrance to your garden. They also attract beneficial insects like bees and butterflies, which can help pollinate your plants and keep other harmful pests under control.
When using companion planting as a natural repellent for tomato hornworm, it’s important to plant the herbs close enough to your tomatoes so that their scent can effectively deter the caterpillars. Planting them in between rows or around the perimeter of your garden can create a natural barrier that keeps these pests at bay.
Companion planting with herbs like basil, borage, or marigolds is an excellent way to naturally control tomato hornworms without resorting to pesticides or other harmful chemicals. By incorporating these companion plants into your planting plan, you can create a healthy and vibrant ecosystem that supports both plant growth and biodiversity.
Bacillus thuringiensis
Bacillus thuringiensis (BT) is a bacterium that produces a toxin that is lethal to many insect pests, including tomato hornworms. BT is available in powder form and can be mixed with water and sprayed onto your plants.
To use BT to kill tomato hornworms, first identify the affected plants and inspect them for signs of infestation. Look for chewed leaves, droppings, and the presence of the caterpillars themselves. Once you have identified the affected plants, mix the BT powder with water according to the instructions on the package.
Next, spray the mixture onto your tomato plants, making sure to cover all surfaces thoroughly. Be sure to target areas where you have seen evidence of hornworm activity. The bacteria in BT will be ingested by the caterpillars as they feed on your plants, causing them to stop eating and eventually die.
One of the benefits of using BT is that it is safe for humans and other animals, making it an ideal choice for organic gardeners like us. Additionally, because it is a naturally occurring bacterium found in soil, it does not harm beneficial insects like bees, lacewings, or ladybugs.
Natural Predators
Several natural predators feed on tomato hornworms, including parasitic wasps, lacewings, and birds like blue jays and chickadees. Encouraging these predators by providing habitat like birdhouses or planting flowers (companion planting, again!) that attract beneficial insects can help keep tomato hornworm populations under control.
If you’re looking to attract parasitic wasps and lacewings to your garden, there are several flowers you can plant that will do the trick. Yarrow, fennel, dill, and cosmos are all great options. These flowers have delicate blooms that attract tiny wasps and other pollinators, as well as lacewings which are attracted to plants with lacy foliage.
Additionally, plants in the carrot family such as caraway and angelica are especially attractive to small parasitic wasps and flies. By planting these flowers in your garden, you’ll be creating a welcoming environment for beneficial insects that will help keep pests under control.
RELATED POST: How to Keep Birds From Eating Tomatoes
Vinegar
Mixing equal parts vinegar and water in a spray bottle can create an effective natural pesticide for controlling tomato hornworm invasions. Spray directly onto the caterpillars to kill them.
- Mix equal parts white vinegar and water in a spray bottle.
- Spray the mixture directly onto the tomato plants, making sure to cover both sides of the leaves.
- Repeat this process every few days until the hornworms are gone.
Vinegar works by disrupting the pH balance on the surface of the leaves, making it difficult for the hornworms to feed and survive. This method is safe for your plants, pets, or kids, and won’t harm beneficial insects.
Garlic Spray
Garlic spray is a potent and eco-friendly option for controlling tomato hornworms in your garden. Packed with sulfur compounds, garlic spray can effectively repel and even kill hornworms without causing harm to beneficial insects or your plants.
To create your own garlic spray, follow these simple steps:
- Peel and roughly chop 10-15 garlic cloves.
- Add the chopped garlic to a blender along with 4 cups of water.
- Blend the mixture until the garlic is fully liquefied.
- Pour the liquid through a fine mesh strainer or cheesecloth into a clean container, discarding any solids.
- Add a few drops of mild liquid dish soap to the strained liquid. The soap acts as a surfactant, helping the garlic spray adhere to the caterpillars and your plants’ surfaces.
- Pour the mixture into a spray bottle for easy application.
When using the garlic spray, be sure to coat both the upper and lower surfaces of your tomato plant leaves, as well as the stems and any visible caterpillars. It’s best to apply the spray in the early morning or late afternoon to prevent potential sun damage to the plants. You’ll need to reapply the spray every few days or after heavy rain to maintain its effectiveness.
Use Row Covers
One of the easiest ways to prevent tomato hornworms from attacking your plants is by using row covers. These covers are made from lightweight fabric and can be placed over your plants to keep the moths from laying their eggs on them. Row covers also protect your plants from other pests like aphids and flea beetles.
But, unless you’ve got covers made from netting with a mesh wide enough to let pollinators through, you’ll need to pollinate by hand or remove the row covers when the flowers appear and use other methods of control.
Pick Them Off By Hand
If you only have a few tomato plants, handpicking the hornworms off the leaves is an effective way to control them. You can wear gloves or use a pair of tweezers to pick them off and drop them into a bucket of soapy water.
Yes, it’s pretty gross, but it’s effective! The tomato hornworm is big and squidgy, but it’s not dangerous, so get stuck in and yank those greedy little suckers off.
Plant Trap Crops
Another way to control tomato hornworm invasions is by planting trap crops like dill, parsley, or fennel around your tomato plants. Oh look – companion planting again! It’s just so useful. These herbs attract parasitic wasps that lay their eggs inside the hornworms, killing them before they can cause damage.
Practice Crop Rotation
Just companion planting, I bang on about crop rotation a lot! But I really can’t overstate its importance in soil and plant health and crop yield. I you don’t rotate crops, you’re asking for all kinds of trouble. Not just with nightshades, either.
Crop rotation is a time-tested agricultural practice that plays a vital role in maintaining soil fertility, preventing the buildup of soil-borne diseases, and managing pests like tomato hornworms, cabbage worms, and other grubs and vegetable-killing pests in an organic garden. The idea behind crop rotation is to change the location of specific plant families in your garden each year, breaking the life cycle of pests and diseases that may have become established in the soil.
For these tomato worms, their life cycle relies on the presence of plants from the nightshade family (tomatoes, potatoes, eggplants, and peppers) as their primary food source. By rotating the planting location of these crops, you can disrupt the hornworms’ life cycle and reduce the likelihood of infestation in the following growing season.
Till the Soil
Tilling the soil is good for soil health (in moderation), helps prepare the soil for planting, and aids in controlling overwintering pests like tomato hornworms. By turning and loosening the soil in between growing seasons, you can expose any hidden pupae or larvae to predators such as birds and beneficial insects, as well as the elements, which can help reduce their survival rate.
Here’s how tilling the soil can contribute to effective pest control:
- Disruption of life cycle: As the tomato hornworm overwinters in the soil as pupae, tilling the soil can unearth and destroy them, effectively disrupting their life cycle and reducing the chances of a new generation of caterpillars emerging in the following growing season.
- Exposure to predators: Turning the soil brings the pupae and larvae closer to the surface, making them more accessible to natural predators like birds, rodents, and beneficial insects. These predators can help keep pest populations in check.
- Improved soil health: Regular tilling can also help maintain soil health by breaking up compacted soil, promoting aeration, and allowing water and nutrients to penetrate more easily. Healthy soil fosters robust plant growth, making your garden less susceptible to pests and diseases.
- Reduction of hiding spots: Tilling the soil can help eliminate weeds and plant debris, which can serve as hiding spots and breeding grounds for pests like the tomato hornworm.
Top tilling tips for pest control:
- Till the soil in the fall after harvesting your crops to expose any overwintering pupae.
- Perform a second tilling in early spring before planting to further disrupt the life cycle of any surviving pests.
- Avoid excessive tilling, as it can damage soil structure and reduce its ability to retain moisture and nutrients. Focus on targeted tilling for pest control purposes and practice other soil management techniques like mulching and cover cropping to maintain soil health.
Use DE
Diatomaceous earth (DE) is a natural powder made from fossilized diatoms that can be used as an insecticide. Sprinkle DE around the base of your tomato plants or directly on the leaves where you see hornworm activity. The powder will stick to their bodies and dehydrate them.
Make Use of Nematodes
Nematodes are another powerful weapon in your organic arsenal against the dreaded tomato hornworm. Beneficial nematodes are microscopic, non-segmented roundworms that play a crucial role in natural pest control. These tiny organisms feed on various insect larvae, including those of tomato hornworms, making them an excellent ally in maintaining a healthy and pest-free garden. Introducing nematodes to the soil around your plants can help control hornworm populations and protect your tomato plants from damage.
These nematodes enter the bodies of the hornworm larvae through natural openings, releasing symbiotic bacteria that multiply and cause the larvae to die within a few days. The nematodes then reproduce inside the dead larvae and move on to search for new hosts, providing ongoing control of hornworm populations.
Try Neem Oil
Neem oil, derived from the seeds of the neem tree (Azadirachta indica), is a powerful, natural pesticide that is effective against a wide range of garden pests, including tomato hornworms. With its unique blend of active compounds, neem oil works by disrupting the growth and development of insects, as well as deterring feeding and reproduction. In addition to its pesticidal properties, neem oil is biodegradable and non-toxic to beneficial insects, making it an eco-friendly option for managing pests in your garden.
Make sure you buy 100% pure, cold-pressed neem oil, then just mix 2 teaspoons of neem to 1 quart of water and add a few drops of liquid dish soap to help the mixture stick. Pour into a spray bottle, shake well, and spray all over your plants. You’ll probably need to reapply every few days until all signs of pests have vanished.
Make an Easy Soap Spray
A simple soap spray made with liquid dish soap and water can also be effective against tomato hornworms. Mix 1 tablespoon of soap with 1 quart of water in a spray bottle and apply it directly onto the leaves where you see activity.
Best Natural Repellent for Tomato Hornworms
The best natural repellent for tomato hornworms is companion planting with herbs like basil or marigolds. These plants emit strong scents that repel many insect pests, including tomato hornworms. I’d also use neem oil, if you don’t have cats. And I go out and pick the blighters off by hand, as with any pest lurking my vegetable garden, I go out at dawn and dusk, pull them off, and drown them in soapy water. Brutal but effective.
FAQs
Do tomato hornworms sting or bite?
No, tomato hornworms don’t sting or bite humans. They may look a bit intimidating with their large size and distinctive appearance, but they are not dangerous to humans. They don’t sting or bite, so there’s no need to worry about being harmed by them. However, they can cause significant damage to tomato plants and other plants in the nightshade family if left unchecked. Tomato hornworms feed on the leaves and stems of these plants, which can lead to defoliation and reduced fruit production. That’s why it’s important to take steps to control these pests before they become a problem in your garden.
Are tomato hornworms poisonous?
No, while they do contain toxins from the plants they consume, they are not poisonous to touch or ingest.
Are tomato hornworms dangerous?
While they may be destructive to your garden if left unchecked, they are not considered dangerous to humans or pets. They do not bite or sting, and they are not poisonous if ingested accidentally. They’re only really dangerous to any nightshades growing in your vegetable garden.
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Incredible capture of the caterpillar. Love the little details. Never knew those wasp larve feed on them.
I will watch out for these in my garden.
Yes, wasps aren’t everyone’s favorite creature, but predatory wasps are really useful in the garden.