If you’ve found large, green caterpillars devouring your tomato plants, you need to know how to get rid of tomato hornworms. These pests can strip a plant bare in just a few days, but effective natural pest control can save your harvest.
This guide will show you safe, organic methods to protect your garden. You won’t need harsh chemicals, just some simple strategies and a bit of regular attention.
How to Get Rid of Tomato Hornworms
Tomato hornworms are the larval stage of the five-spotted hawkmoth. They are large, up to four inches long, and bright green with white V-shaped marks and a black “horn” on their rear.
They blend in perfectly with stems and leaves, making them tricky to spot. Their damage, however, is obvious: missing leaves, chewed stems, and even damaged fruit.
Why Choose Natural Control?
Chemical pesticides kill beneficial insects like bees and ladybugs. Natural methods target the pest while keeping your garden’s ecosystem healthy and your food safe to eat.
It’s also more sustainable. You’re working with nature, not against it, which often provides a longer-term solution.
Step 1: The Daily Hand-Picking Patrol
This is the most immediate and effective method. Go out to your garden in the early morning or evening when they are most active.
- Look for dark green droppings on leaves below. Look up from there to find the culprit.
- Wear gloves if you prefer, and simply pick them off the plant.
- Drop them into a bucket of soapy water to dispose of them. Check your plants every day during peak season.
Step 2: Encourage Natural Predators
Many insects and birds see hornworms as a tasty meal. Invite these helpers into your garden.
- Braconid Wasps: These tiny parasitic wasps are a hornworm’s worst enemy. They lay eggs on the caterpillar, and the larvae feed on it. If you see a hornworm with white rice-like cocoons on its back, leave it! The wasps will hatch and continue their work.
- Ladybugs & Lacewings: They eat hornworm eggs and small larvae. Plant dill, fennel, and yarrow to attract them.
- Birds: Encourage birds like robins and sparrows with a birdbath or feeder nearby. They will gladly pick off caterpillars for you.
Step 3: Use a Safe Organic Spray (Bt)
Bacillus thuringiensis, or Bt, is a naturally occurring soil bacteria. It’s completely non-toxic to people, pets, and beneficial insects.
When a hornworm eats leaves treated with Bt, it stops feeding and dies within a few days. It’s very effective against young caterpillars.
- Purchase a liquid Bt formulation (often called “Thuricide” or “Dipel”).
- Mix it with water according to the package directions.
- Spray it thoroughly on all plant surfaces, especially the undersides of leaves. Reapply after rain.
Step 4: Till Your Garden Soil
Hornworms overwinter as pupae in the soil. After the growing season ends, till your garden bed deeply.
This exposes the pupae to cold weather and birds, disrupting their life cycle. This simple fall or early spring task can drastically reduce next year’s population.
Companion Planting for Prevention
Some plants naturally repel the moths that lay hornworm eggs. Interplant these with your tomatoes:
- Basil: Its strong scent masks the smell of tomato plants.
- Borage: Repels the tomato hornworm moth and attracts beneficial wasps.
- Marigolds: Their roots exude a substance that deters many soil pests.
- Dill: While it attracts hornworms (making them easier to find), it also attracts the predatory wasps that kill them.
Step 5: Use a UV Blacklight at Night
Hornworms glow a bright green under ultraviolet (UV) light. This is a secret weapon for night hunting.
Take a small handheld UV flashlight into the garden after dark. The caterpillars will light up, making them incredibly easy to spot and remove. It’s a very efficient method for large gardens.
What Not to Do: Common Mistakes
Avoid these errors that can make the problem worse or harm your garden.
- Don’t use broad-spectrum insecticides. They kill the good bugs that are helping you.
- Don’t ignore small holes or droppings. Early detection is key to easy control.
- Don’t plant tomatoes in the same spot every year. Rotate your crops to break the pest cycle.
Identifying Hornworm Damage Quickly
Knowing the signs early gives you a head start. Look for these clues:
- Large sections of leaves missing, starting from the top of the plant.
- Stems that are bare, with only the central vein remaining.
- Black or dark green droppings (frass) on leaves below the damage.
- Sometimes, you’ll see scars or holes on the tomatoes themselves.
Frequently Asked Questions (FAQ)
Are tomato hornworms poisonous?
No, they are not poisonous to humans or pets. The “horn” is just for show and cannot sting. However, they can be toxic if they have been feeding on toxic plants like nightshade, so it’s best not to handle them with bare hands and always wash up afterwards.
What is the difference between a tomato hornworm and a tobacco hornworm?
They are very similar and both eat tomato plants. The tomato hornworm has eight V-shaped white marks and a black horn. The tobacco hornworm has seven diagonal white stripes and a red horn. Control methods for both are exactly the same.
What plants do hornworms eat besides tomatoes?
They also favor other plants in the nightshade family. This includes peppers, eggplants, potatoes, and tobacco. If you have an infestation, check all these plants in your garden carefully.
Will dish soap and water kill hornworms?
A simple soap spray can suffocate small, soft-bodied insects but is less effective on large, tough caterpillars like hornworms. It’s better to use hand-picking or Bt for them. Soap spray can help control the eggs though.
How do I prevent hornworms naturally?
Prevention relies on a combination of tactics: till your soil in fall, use companion planting, encourage predators, and inspect your plants regularly from early summer. A diverse, healthy garden is your best defense.
Dealing with tomato hornworms can be frustrating, but it’s very manageable. The key is consistency. A quick daily check, combined with these natural strategies, will keep your plants healthy. Your reward will be a plentiful, chemical-free tomato harvest for you and your family to enjoy.