Tomato hornworms are a common garden pest that can quickly defoliate tomato plants. Getting rid of these large caterpillars takes some persistence, but is possible through a combination of physical removal, barriers, biological controls, and organic sprays. With a multi-pronged approach, you can protect your tomato crop from damage by tomato hornworms.

Identifying Tomato Hornworms

The first step in controlling tomato hornworms is learning how to identify them. There are some key characteristics to look for:

Large size – Tomato hornworms can grow up to 4 inches long when fully mature. They are one of the largest caterpillar pests.
Green color – They have a green color that blends in well with tomato foliage, making them harder to spot. Look closely to find them.
White V-shaped marks – There are white markings along the sides that look like a “V” shape. This helps distinguish them from other green caterpillars.
Horn on rear – They have a small horn that protrudes from their rear end. This is how they got the name “hornworm.”
Damage – Check for defoliated areas, chewed leaves, stems, and fruits. Frass (caterpillar poop) on damaged areas is a telltale sign.

Carefully inspect the undersides of leaves and inside stems where the hornworms like to hide during the day.shake digestive chemical substances from their bodies at an attacker. Some people also are sensitive to contact with the hairs. So dislodging them needs care.

Hand Picking Tomato Hornworms

One of the most effective organic methods for controlling tomato hornworms is to manually remove them from plants. Here are some tips:

Wear gloves to protect your hands from irritation from the hairs. Use tweezers or forceps if needed.
Inspect plants thoroughly, at least every 2-3 days during peak hornworm season.
Look on undersides of leaves, inside furled leaves, under branches, and inside growing stems where hornworms like to hide.
Gently crush the hornworms or put them into a bucket of soapy water to kill. You can also slice them in half with pruners or scissors.
Dispose of the dead hornworms far away from the garden so they don’t attract more. Putting them in sealed containers helps keep predators away.
Be sure to check all parts of the plant, as one plant can house several hornworms.
Enlist help from others – having multiple sets of eyes increases the chances of finding all the hornworms.
Check in the morning or evening when the caterpillars are most active and feeding.

Regular handpicking is time consuming but can easily eliminate light or moderate infestations before serious damage occurs. Combine with other methods for best control.

Biological Controls for Tomato Hornworms

Introducing natural predators into the garden is an organic way to control tomato hornworm populations. The main biological controls include:

Trichogramma Wasp

These tiny wasps lay their eggs inside hornworm eggs, killing the larvae before they can hatch and damage plants. Releasing them early in spring provides control through the season.

Available as parasitized hornworm egg cards from garden supply stores.
Hang the cards on tomato plants where hornworms have been previously spotted.
One card per plant is sufficient, released every 2-3 weeks.
Effective against eggs and young larvae before they grow large.

Braconid Wasp

The braconid wasp lays eggs on tomato hornworms which then kill the caterpillar from the inside. Look for hornworms with white cocoons sticking out of them – leave those in place for the wasps to hatch.

Naturally occurs in gardens but releasing extra provides better control.
Can be purchased from garden supply outlets and released onto plants.
The adult wasp will continually lay eggs on additional hornworms all season long.

Bacillus Thuringiensis (Bt)

Bt is a bacteria that kills hornworms when they ingest it but is safe for other insects and animals. It must be reapplied frequently as it breaks down in sunlight.

Available as a powder or liquid concentrate spray.
Treat plants as soon as hornworm damage is noticed.
Reapply every 1-2 weeks and after rain.
Most effective on young larvae so regular treatments are needed.

Entomopathogenic Nematodes

These microscopic roundworms kill caterpillars from the inside but won’t harm plants or other insects. They can be applied to soil or sprayed onto foliage.

Available from garden stores, best to get local species adapted to your area.
Apply at first sign of hornworm damage.
Reapply every 2-3 weeks as protection decreases over time.
Less effective on larger hornworms, so start early.
Work best in cooler, moist conditions. Avoid hot, dry weather.

Tachinid Fly

The tachinid fly lays eggs on tomato hornworms which then bore inside and feed, killing the host. The adult flies look similar to houseflies but do not bite or sting humans.

Can be purchased from garden suppliers and released.
Females continually lay eggs throughout summer.
More effective against larger larvae.
Allow any parasitized hornworms to remain in the garden to complete their life cycle.

Using a combination of these biological controls can provide ongoing, natural protection against tomato hornworms. Timing the releases correctly provides caterpillar control through all life stages for an effective integrated pest management program.

Organic Sprays for Tomato Hornworms

There are also some organic home remedy sprays that can be applied directly to plants to kill tomato hornworms:

Neem Oil

Neem oil comes from the nuts of the neem tree. It smothers soft-bodied insects and makes plants unpalatable.

Mix 1-2 tablespoons neem oil per gallon of water with a small amount of insecticidal soap.
Spray leaves including the undersides, stems, and fruits.
Apply in the early morning or late evening every 1-2 weeks.
Can also deter feeding and act as an ovipositional deterrent on eggs.

Spinosad

Spinosad is a biological insecticide derived from a naturally occurring soil bacteria. It must be sprayed directly onto caterpillars to be effective.

Mix according to label directions, usually 1-2 tbsp per gallon of water.
Thoroughly coat leaves, stems, and fruits.
Reapply weekly for young larvae, or every 2-3 weeks for larger hornworms.
Most effective on small, early instars so regular applications are needed.
Can also treat eggs and be used as a barrier spray.

Garlic Spray

Garlic acts as a natural insect repellent. An oil spray can deter feeding by hornworms.

Crush 4-5 garlic cloves and steep in 1 quart of warm water for 1 hour.
Strain and mix the garlic water with 2 tsp insecticidal soap.
Add 1 tbsp baking soda and shake well until dissolved.
Pour into spray bottle and apply to plants, coating all surfaces.
Reapply every 5-7 days after watering.
The garlic smell may deter egg laying as well.

Hot Pepper Spray

Capsaicin in hot peppers burns soft tissue of insects. It causes irritation and prevents feeding.

Blend 1 cup chopped hot peppers with 2 cups water.
Allow to steep for 24 hours then strain.
Add 1-2 tsp liquid soap to help the spray stick.
Apply liberally to fully coat plants.
Reapply every 7-10 days or after rain.

Be sure to wear gloves and avoid touching your face/eyes when applying any of these organic sprays to prevent skin irritation. Spray in the early morning or evening to prevent leaf burn. Sprays are most effective against young larvae and must contact the insects to work. Rotate between different options to prevent resistance.

Physical Barriers Against Tomato Hornworms

There are some physical barriers that can be implemented in the garden to prevent tomato hornworms from accessing plants:

Row Covers

Floating row covers of fine mesh screen out the adult moths from laying eggs on plants.

Drape over tomato cages, hoops or supports to create a tent.
Secure tightly around the bottom to prevent entry.
Maintain throughout season until ready to pollinate, then remove.
Provides a physical rather than chemical barrier.

Collars

Barrier collars wrapped around each plant stem prevent caterpillars from climbing up onto the plant from the ground.

Cut cardboard, felt, or flexible plastic to fit snugly around stems.
Cover with tape or staples to seal any gaps.
Ensure collars are loose enough not to restrict growth.
Check underside for caterpillars trying to breach the barrier.
Keep soil cultivated around collars to disrupt any underground burrowing.

Tanglefoot

Sticky barrier pastes like Tanglefoot can be applied to stems to trap small larvae trying to climb plants.

Apply a thick layer around each stem, about 2-4 inches wide.
Reapply every 2 weeks to keep the material sticky.
Prevents young caterpillars from reaching foliage but doesn’t stop larger ones.
Other options include duct tape sticky side out or non-drying glue barriers.

While barriers work best against young hornworms, they can help reduce damage when used along with other organic methods in an integrated pest management plan.

Cultivation Practices That Deter Tomato Hornworms

Certain garden practices can also help deter tomato hornworms or limit their damage:

Remove all plant debris and fallen fruits from the garden after harvest. This eliminates overwintering sites for pupae in the soil.
Till up the garden soil thoroughly in fall to disrupt any hornworm pupae. Exposure destroys many.
Rotate tomato planting locations each year to break pest cycles. Avoid replanting in previously infested areas.
Weed the garden regularly and remove any solanaceous weeds like horsenettle which can harbor hornworms.
Use drip irrigation rather than overhead watering to keep foliage dry and prevent fungal diseases.
Avoid excessive nitrogen fertilizers that produce succulent, tender growth attractive to hornworms.
Monitor for eggs and young larvae weekly and use control methods early before populations explode.
Pick tomatoes as soon as ripe to prevent caterpillars from entering and destroying fruits.
Plant marigolds, onion, garlic or other companion plants that may deter moths.

A clean garden and vigilant crop monitoring are important to prevent tomato hornworms from ever taking hold. If detected early, light infestations can be controlled before plants suffer major defoliation.

When to Call for Professional Help with Tomato Hornworms

While the methods described can help manage tomato hornworms organically, severe infestations may require other options:

If handpicking large numbers of hornworms daily but damage continues, the infestation is too high for this method alone.
If biological controls have been released per directions but populations are still rising, additional control is needed.
If plants show signs of excessive defoliation (over 30%) even after sprays, the hornworms are out of control.
If caterpillars have entered fruits internally, insecticides are required immediately to save the crop.
If you are unable to effectively monitor and treat the infestation due to size or access issues, professional intervention may be required.

In these cases, contacting a licensed pest control operator to apply Bt or synthetic insecticides may be warranted to control heavy tomato hornworm populations. They have the equipment and training needed for maximum effectiveness.

Tomato Hornworms – Final Thoughts

Tomato hornworms can be alarming pests, but don’t let them discourage you from growing tomatoes! With regular inspection and a combination of removal, barriers, biological controls, and organic sprays, you can protect your crop. Practicing good garden sanitation and crop rotation are also important preventive measures. Move quickly if populations explode to avoid serious losses. A persistence, integrated approach will provide effective organic tomato hornworm control without sacrificing the health of people, pets, beneficial insects, or the environment.

Frequently Asked Questions About Tomato Hornworms

How do tomato hornworms damage plants?

Tomato hornworms are voracious leaf feeders. They use their chewing mouthparts to eat leaves, stems, buds, and even green tomatoes. This defoliation can quickly strip plants if heavy infestations go uncontrolled. Hornworms also leave behind frass (caterpillar droppings) which promotes fungal issues.

What do tomato hornworm eggs look like?

The adult tomato hornworm moth lays its tiny eggs singly on the undersides of leaves. They are round and pale yellow, about the size of the tip of a pencil eraser. Eggs hatch in 3-10 days into larvae which immediately start feeding.

How fast do tomato hornworms grow?

Tomato hornworms grow rapidly, molting 5 times over 2-3 weeks until reaching full size. After hatching they may be only 1⁄8 inch long but at maturity can reach 4 inches. Their massive appetite allows for this exponential growth in a short period.

Do tomato hornworms bite or sting?

While tomato hornworm caterpillars may look intimidating with their large size and horn, they do not bite or sting humans. The horn is harmless. However, they do have microscopic irritating hairs that can cause skin irritation in some people so gloves should be worn when handling.

What is the tomato hornworm lifecycle?

Tomato hornworms overwinter as pupae in the soil. The adult moths emerge in spring and lay eggs on tomato plants. The caterpillars hatch and feed for 2-3 weeks before burrowing into soil to pupate. A second generation then repeats the cycle, with moths appearing in late summer.

What eats tomato hornworms naturally?

Tomato hornworms have many natural predators. Birds, parasitic wasps, predatory insects, spiders, and reptiles all prey on various life stages. Diseases like viruses and nematodes also help regulate populations. Promoting biodiversity encourages these beneficial controls.

Are tomato hornworms poisonous to humans?

While it would certainly be unpleasant, tomato hornworms are not poisonous if ingested. However, the plants they feed on absorb toxins from the caterpillar’s diet, making them potentially poisonous to consume. Accidentally eating a hornworm will not cause harm beyond the gross factor!

What temperature kills tomato hornworms?

Tomato hornworms thrive in warm weather between 70-90°F. Temperatures below 55°F or above 95°F will kill eggs and small larvae. Sustained freezing temperatures are required to destroy overwintering pupae in the soil. High heat can have adverse effects on biological controls as well.

Can you tell the difference between a tobacco hornworm and a tomato hornworm?

While similar in appearance, the tobacco hornworm has seven white diagonal lines on its body rather than the V-shaped markings of the tomato hornworm. Tobacco hornworms also have a reddish horn while tomato horns are black. But both can damage tomato plants so should be removed.

Conclusion

Tomato hornworms can decimate plants quickly if left unchecked. But with close monitoring and early intervention using a combination of removal, barriers, beneficial insects, and organic sprays, tomato lovers can defend their crops. Prevention is also key through garden sanitation, plant health, and disruption of the hornworm lifecycle. A diligent integrated pest management approach can successfully protect tomatoes from these voracious pests without harmful chemicals. With the right knowledge and persistence, gardeners can safely get rid of tomato hornworms and enjoy a bountiful, worm-free tomato harvest.

How to Get Rid of Tomato Hornworms