Tomato hornworms are one of the most destructive pests you can encounter when trying to grow tomato plants. These large caterpillars are voracious eaters that can munch their way through entire plants in a matter of days.
It’s easy to identify tomato hornworms due to their distinctive appearance, and you may notice the signs of hornworm damage before you spot the actual pests.
To get rid of tomato hornworms naturally, methods include manual removal, treating them with Bt, or making your own DIY spray. You can also treat your tomato plants with a chemical pesticide to kill tomato hornworms quickly.
What Are Tomato Hornworms?
Tomato hornworms are a type of large caterpillar that are common pests to vegetable gardens throughout the US. These pests are actually the larval stage of the sphinx or hummingbird moth.
Tomato hornworms like to feed on the leaves, fruits, and stems of many different plants, but have a particular preference for those in the nightshade family. In addition to tomatoes, their diet includes eggplant, potatoes, and peppers.
Tomato Hornworms Life Cycle
As we’ve mentioned, tomato hornworms are the larval stage of the hummingbird moth. The lifecycle of these pests is as follows:
1. Adult Moths Lay Eggs
The lifecycle of a tomato hornworm begins in the late spring when adult hummingbird moths lay their eggs on the undersides of plant foliage. As is their dietary preference, the adult moths lay their eggs on plants in the nightshade family, including tomatoes, eggplants, peppers, and potatoes.
2. Eggs Hatch into Tomato Hornworm Larvae
After about a week, the eggs hatch into the hornworm caterpillar larvae. The tomato hornworm larvae then feed voraciously for 4 to 6 weeks, eating the nightshade plants they have a preference for. The larvae grow to become sizeably large caterpillars.
3. Tomato Hornworm Larvae Enter Pupae Stage
After 4 to 6 weeks of feeding, the tomato hornworm larvae burrow into the soil and form a cocoon. During this stage, the caterpillars’ bodies disintegrate and regenerate into their adult moth form. This process can take as little as 2 to 3 weeks if the weather is warm enough.
4. Tomato Hornworm Pupae Become Adult Moths
Once they finish the pupal stage, the eggs hatch to give way to the new adult moths. These moths can be hard to spot as they are most active from the evening in the early morning. During these hours, they feed on the nectar of different flowers. The adult moths then lay more eggs, starting the cycle all over again.
Signs of Tomato Hornworm Damage
The signs of tomato hornworm damage on your tomato plants appear initially on the plants’ leaves, before showing up on the actual tomatoes.
Damage to the Tomato Plants’ Leaves
On your tomato plants, tomato hornworm damage typically starts at the tips of the plant. The hornworms will eat the leaves of the tomato plants, working their way down the foliage. These pests are voracious eaters and can consume every leaf on a tomato plant in a matter of days.
A severe infestation of hornworms can cause the complete defoliation of a tomato plant, leaving the plant’s stem completely bare of any leaves. They usually begin feeding on tomato plant foliage during the midsummer and may continue to feed throughout the growing season to the time of harvesting. Another sign to look out for is black droppings on the leaves of your tomato plant; the hornworms leave these black droppings behind as they feed on the plants.
Damage to the Tomato Fruits
After they have consumed every leaf on the tomato plant, tomato hornworms will move onto the actual tomatoes.
While worms burrow holes into tomatoes, tomato hornworms don’t do this. They instead feed on the tomatoes’ exterior, creating large, open welts on the fruits, rendering the tomatoes inedible. They feed on both the unripe and ripe tomatoes and can consume many in a short period of time.
How to Identify Tomato Hornworms
Tomato hornworms look like large caterpillars, growing to be up to 5 inches long. They have pale green bodies with markings of black and white, having 8 white V-shaped stripes along their back. Tomato hornworms also have a red horn-like protrusion that stems from their rear end; although this protrusion looks threatening, hornworms aren’t able to sting or bite you.
How to Get Rid of Tomato Hornworms
To get rid of tomato hornworms naturally, you can pick them off by hand, treat the plants with Bt, or create your own DIY organic hornworm repellent. As a last resort, you can use a chemical pesticide to kill tomato hornworms on your tomato plants.
Pick Worms Off By Hand
The most direct way to get rid of tomato hornworms is to simply pick them off your tomato plants by hand. This method is ideal if you have a small garden or a minor infestation of the pest.
Inspect your tomato plants for the hornworms, focussing on the stems and the tops and undersides of leaves. Pick off all of the hornworms that you can see. Although they have spikey bodies, they don’t sting and they also don’t bite, so you can do this with your bare hand. If you’re squeamish, wear a pair of gloves or pick them up using tongs.
After picking off the hornworms, crush them or place them into a bucket of soapy water to kill them. If you have them, you can alternatively feed the hornworms to your chickens.
Apply Bt to Tomatoes
For more severe infestations, you can kill tomato hornworms by treating your tomato plants with Bacillus thuringiensis, or Bt. This is a bacteria that naturally occurs in soil.
When the tomato hornworms consume Bt, the bacteria paralyzes the pests’ digestive system. This prevents them from feeding and eventually causes them to die off. You don’t need to worry about harming other lawn-friendly insects such as bees, as Bt is only harmful to caterpillars.
Using Bt to kill tomato hornworms is most effective when the larvae are smaller. There are many strains of this bacteria; for recommendations on which strain is most effective to kill tomato hornworms, get in contact with your local garden center or extension office.
Make Your Own DIY Tomato Hornworm Repellent
Another way to get rid of tomato hornworms naturally is to create your own DIY repellant. You can use this remedy in place of a harsh chemical pesticide.
Make a mixture of dishwashing soap and water and place it into a spray bottle. Spray the mixture onto the foliage of the infested tomato plants. After spraying the plants, sprinkle some cayenne pepper over the foliage and fruit while it’s still wet. The soap spray will kill the tomato hornworms currently on your plants, while the pepper works to repel new pests entering your garden. You’ll need to repeat applications of this treatment after each heavy rain to maintain its efficacy.
Use a Chemical Pesticide
Chemical pesticides are an effective way to kill tomato hornworms. However, you should only use chemical products as a last resort when all other natural options fail to work or if you have a particularly severe infestation.
How to Prevent Tomato Hornworms
In order to prevent reinfestations of tomato hornworms, you should incorporate tilling into your annual gardening routine. You can also encourage the presence of natural hornworm predators to keep these pests at bay.
Till Soil Annually
If you have a recurring issue with tomato hornworms, you should make a point of tilling your soil twice annually. Use a rototiller to till the soil first in the spring before planting, then again in the late fall.
The tilling action will bury or destroy the pupae, preventing them from becoming adult egg-laying moths; this disrupts the tomato hornworms’ life cycle, reducing the chances of a reinfestation of the pest. Also, tilling in the fall allows you to till your old growth into the soil where it becomes an organic fertilizer. This gives your soil a boost of nutrients over winter which your new plants can use in the spring.
Encourage Presence of Natural Hornworm Predators
There are several natural predators that will eat tomato hornworms. Encouraging the presence of these creatures will help to keep hornworm populations low.
Many types of birds eat tomato hornworms, such as crows and owls. Encouraging these birds to your garden may help to prevent tomato hornworm infestations; however, you should keep in mind that these birds may also feed on your tomatoes. If you have chickens, you can let them loose in your tomato patch and they’ll eat up the hornworms.
More effective predators of tomato hornworms are several types of parasitic braconid wasps. These wasps attach their eggs to the backs of the tomato hornworms; when the eggs hatch, the wasp larvae feed on the hornworms which eventually causes them to die. If you notice there are hornworms covered in tiny white egg sacks, leave these to be. The eggs will hatch into a population of wasps that will help to keep hornworm infestations at bay. To attract braconid wasps, plant dill, clover, fennel, or sweet asylum in your garden.
More FAQs About Tomato Hornworms
Where Do Tomato Hornworms Come From?
As we’ve explained, tomato hornworms come from eggs laid by the hummingbird moth.
While the larvae are drawn to plants in the nightshade family, adult moths are drawn to plants with large, fragrant flowers that bloom at night, such as moonflower, evening primrose, and four o’clocks. If you have plants that attract both the larvae and adult forms of the hornworms, your garden will likely attract these pests.
Where Do Tomato Hornworms Go During the Day?
Tomato hornworms are most active during the evening and early morning when air temperatures are cooler. During the day, they will hide underneath leaves and the interior stems of plants to escape the sun.
Are Tomato Hornworms Poisonous?
Although they have a threatening protrusion on their bodies, tomato hornworms are not poisonous. They aren’t able to sting or bite you, and you can pick them off with a bare hand without a problem.
Are Tomato Hornworms Poisonous to Dogs?
Tomato hornworms are not poisonous to dogs. Some dogs may even seek out and eat the tomato hornworms, helping to keep populations at bay.