The most common worms on tomatoes and how to spot them

The worms you see on tomato plants are usually one of three species: the tomato hornworm, the fruitworm (also called the corn earworm), or the cutworm. Hornworms are large green caterpillars with white stripes and a horn-like tail; they can grow to 4 inches long and eat leaves and fruit. Fruitworms are smaller, yellowish-brown, and tunnel directly into the fruit, leaving holes and rot. Cutworms are gray or brown and hide in soil during the day, cutting through seedling stems at ground level.

Check your plants every few days, especially the undersides of leaves where hornworms hide. Look for dark droppings on leaves (a sign of feeding), holes in fruit, or wilted stems near the soil. Early detection makes removal much easier and prevents a small problem from becoming an infestation.

Key Takeaways

  • Hornworms and fruitworms can be removed by hand or treated with Bacillus thuringiensis (Bt), a natural bacterial spray that kills caterpillars without harming other insects.
  • Neem oil and insecticidal soap work on smaller worms and younger caterpillars but are less effective on large hornworms.
  • Cutworms are best prevented by placing cardboard collars around seedling stems at planting time or by removing debris where they hide.
  • Removing infested fruit and fallen leaves stops worms from completing their life cycle and returning next season.
  • Companion planting with basil, marigolds, and borage attracts natural predators like parasitic wasps that lay eggs inside worms.

Hand-picking and removing infested fruit

The simplest method for light infestations is to pick worms off by hand. Wear gloves, search the plant thoroughly (especially the top 12 inches where hornworms congregate), and drop worms into a bucket of soapy water. Check every 2 to 3 days until you stop finding new ones. This works best when you catch the problem early, before worms are large or numerous.

Remove any fruit with holes or soft spots when ready, even if the worm is not visible inside. Fallen fruit and leaves on the ground are where worms pupate and overwinter, so collect and discard them (or bury them deep in a compost pile that reaches 140°F). Do not leave debris under the plant.

Bacillus thuringiensis (Bt) spray for larger infestations

Bacillus thuringiensis, sold under brand names like Monterey Garden Insect Spray and Safer Brand, is a naturally occurring soil bacterium that kills caterpillars by destroying their digestive system. It works on hornworms, fruitworms, and other caterpillars but does not harm bees, ladybugs, or other beneficial insects. Spray in the early morning or late evening when caterpillars are most active.

Mix according to the label (usually 1 to 2 tablespoons per gallon of water) and spray the entire plant, coating both the tops and undersides of leaves. Reapply every 7 to 10 days or after rain. Bt works best on young caterpillars; large hornworms may require hand-picking in addition to spraying. Results typically appear within 3 to 5 days as caterpillars stop feeding and die.

Neem oil and insecticidal soap for smaller worms

Neem oil, derived from the neem tree seed, disrupts the feeding and reproduction of soft-bodied insects and young caterpillars. It is less effective on large hornworms but works well on fruitworms and cutworms when they are small. Spray every 7 days, always in early morning or evening, and avoid spraying during the hottest part of the day to prevent leaf burn.

Insecticidal soap (potassium fatty acids) works similarly on small caterpillars and aphids by breaking down their outer coating. Both products break down quickly in sunlight and rain, so frequent reapplication is necessary. Follow label directions carefully, as overuse can damage plant leaves and reduce fruit yield.

Preventing cutworms at planting time

Cutworms hide in soil and emerge at night to sever seedling stems just above the soil line. The best prevention is a physical barrier placed at planting time. Cut a toilet paper tube or paper towel tube into 2-inch rings and slide one around each seedling stem, pushing it 1 inch into the soil and leaving 1 inch above. Alternatively, wrap aluminum foil loosely around the stem or use a plastic cup with the bottom cut out.

Remove mulch and debris in a 4-inch radius around each seedling, since cutworms hide under dead leaves and straw. If cutworms have already damaged seedlings, dig 1 to 2 inches into the soil around the base of the plant to find and remove them by hand. Water in the morning rather than evening, as wet soil at night attracts cutworms.

Companion plants and natural predators

Planting basil, marigolds, and borage near tomatoes attracts parasitic wasps, which lay eggs inside hornworms and fruitworms. The wasp larvae consume the worm from the inside, killing it. These plants also repel some flying insects and add flavor or beauty to the garden. Plant them at the same time as tomatoes or a few weeks before.

Leaving a small area of native plants or wildflowers nearby supports ground beetles and spiders, which hunt cutworms and other soil-dwelling pests. Avoid broad-spectrum insecticides, which kill these beneficial insects along with the pests.

When to use chemical insecticides

If natural methods are not controlling the infestation and fruit damage is severe, spinosad (a naturally derived insecticide) or pyrethrin (from chrysanthemum flowers) can be used. Both kill a wide range of insects, so spray only the affected areas and only in early morning or evening to minimize harm to bees. Always follow label directions for timing before harvest; most require 1 to 7 days between the final spray and picking fruit.

Avoid broad-spectrum synthetic insecticides like carbaryl or permethrin on tomatoes, as they kill beneficial insects and can cause mite outbreaks. If you do use them, use the lowest concentration listed on the label and the longest pre-harvest interval to reduce residue on fruit.

Frequently Asked Questions

Can I eat a tomato with a small hole in it from a worm?

A small surface hole is usually safe to cut out and discard, then eat the rest. If the hole is deep or the fruit is soft inside, the worm has likely contaminated the interior with bacteria, so discard the whole fruit. When in doubt, throw it away.

What time of year do tomato worms appear?

Hornworms and fruitworms emerge when nighttime temperatures stay above 50°F, usually mid-summer through early fall. Cutworms appear earlier, in spring and early summer, targeting seedlings. Check plants regularly from transplant time through the end of the season.

Do I need to spray the whole plant or just the affected areas?

Spray the entire plant, including the undersides of leaves, because worms hide in areas you cannot see. Partial spraying leaves hiding spots where worms survive and continue feeding. Thorough coverage is especially important with Bt and neem oil.

How long does it take for Bt to kill worms?

Bt stops worms from feeding within hours, but visible death usually takes 3 to 5 days. You may see worms stop moving and turn dark before they fall off the plant. Continue spraying every 7 to 10 days to catch any new worms that hatch from eggs.

Will removing worms by hand hurt the plant?

No. Gently pulling a worm off a leaf or stem causes no lasting damage to the plant. The plant recovers quickly. Hand-picking is safe, free, and often the fastest way to stop feeding damage if you catch the problem early.