The fastest way to stop caterpillars on tomato plants

The most effective when ready action is to pick caterpillars off by hand and drop them into soapy water. Check the undersides of leaves and around the stem where they hide during the day. This works best when you catch them early, before they've eaten much of the plant or grown large enough to be hard to spot.

If you have only a few plants or a small infestation, hand-picking is often enough. It costs nothing, harms no other insects, and takes 10 to 15 minutes per plant. Do this every two or three days for a week to catch new caterpillars as they hatch.

For larger infestations or if you prefer not to handle them, Bacillus thuringiensis (Bt) is a bacterial spray that kills caterpillars but is safe for humans, pets, and beneficial insects. Spray it directly on the leaves and stems where you see damage or caterpillars. It works best on young caterpillars and must be reapplied after rain or every 7 to 10 days.

Key Takeaways

  • Hand-picking caterpillars into soapy water is the fastest and cheapest method for small infestations.
  • Check the undersides of leaves and around stems every two or three days, since caterpillars hide during daylight.
  • Bacillus thuringiensis (Bt) spray kills caterpillars on contact and is safe for people and pets.
  • Neem oil and insecticidal soap work on soft-bodied caterpillars but may require multiple applications.
  • Remove fallen leaves and debris around plants to eliminate hiding spots where caterpillars pupate.

Identifying which caterpillars are eating your tomatoes

The most common tomato pest is the tomato hornworm, a large green caterpillar with white stripes and a horn-like projection on its rear. They can grow to 4 inches long and eat large holes in leaves and fruit. You'll often see dark droppings on leaves below where they're feeding.

The fruitworm (also called the corn earworm) is smaller, about 1 inch long, and ranges from green to brown. It burrows into the fruit itself rather than just eating leaves, making it harder to spot until you cut into a tomato.

Other caterpillars that feed on tomatoes include the cabbage looper, which is pale green and moves by arching its back, and various moth larvae. The treatment method is the same regardless of species: remove them or spray with Bt.

Using Bacillus thuringiensis spray correctly

Bt is a naturally occurring soil bacterium that produces a toxin lethal to caterpillars but harmless to mammals and birds. It's sold under brand names like Monterey Garden Insect Spray, Safer Brand BtK, and Bonide Bt. You'll find it at garden centers, hardware stores, and online retailers.

Spray in the early morning or late evening when caterpillars are most active and beneficial insects like bees are less likely to be on the plant. Mix according to the label instructions and spray until the leaves are wet but not dripping. Focus on the undersides of leaves, where caterpillars feed.

Reapply every 7 to 10 days or after rain. Bt works slowly—caterpillars stop eating within hours but may take 2 to 3 days to die—so don't expect when ready results. It's most effective on young caterpillars; large hornworms may survive a single process.

Neem oil and insecticidal soap for smaller caterpillars

Neem oil is derived from the neem tree and disrupts the feeding and reproduction of soft-bodied insects. It's less toxic than synthetic pesticides but can harm some beneficial insects if sprayed directly on them. Spray in early morning or evening, coating both sides of leaves.

Insecticidal soap works by breaking down the outer layer of soft-bodied pests like young caterpillars and aphids. It has no residual effect, so it only kills insects it contacts directly. Like neem, it's safest applied when pollinators are not active.

Both neem and soap require repeated applications—usually every 7 to 14 days—and work best on caterpillars smaller than 1 inch. Larger hornworms have tougher skin and may survive treatment. Always follow label directions, as some formulations can damage plants if applied in direct sun or extreme heat.

Removing caterpillar hiding spots and preventing future infestations

Caterpillars pupate in soil and leaf litter around the base of plants. Remove fallen leaves, dead plant material, and weeds where pupae can overwinter. In fall, after you've harvested, clear away all plant debris and turn over the soil around where tomatoes grew.

Handpick egg clusters before they hatch. Hornworm eggs are small, round, and usually laid on the underside of leaves. Fruitworm eggs are smaller and harder to spot, but removing visible clusters reduces the next generation.

Plant tomatoes in a different location each year if possible, since some caterpillar pupae survive in the soil. Companion plants like basil and marigold may deter some pests, though this is not a reliable control method on its own.

When to call for help or consider professional treatment

If your tomato patch is large or you have a severe infestation that hand-picking and Bt haven't controlled after two weeks, contact your local cooperative extension office. They can identify the specific pest and recommend treatments suited to your region and the time of season.

Professional pest control services can explore stronger insecticides, but these are usually unnecessary for home gardeners and may harm beneficial insects. Most caterpillar problems on tomatoes are manageable with the methods above.

If you're uncomfortable handling caterpillars or spraying, ask a neighbor or family member to help, or focus on removing fallen leaves and debris to reduce next year's population.

Frequently Asked Questions

Can I use regular insecticide on caterpillars?

Yes, but it's not necessary. Synthetic insecticides kill caterpillars faster than Bt but also harm beneficial insects like bees and ladybugs. Bt and hand-picking are usually enough for home gardens and protect the insects that eat other pests.

Will caterpillars come back after I remove them?

Yes, if moths are still laying eggs on your plants. Caterpillars hatch in waves over several weeks. Continue checking plants every few days and remove new caterpillars as they appear, or reapply Bt on schedule to catch them as they hatch.

Is it safe to eat tomatoes after spraying Bt?

Yes. Bt breaks down quickly in sunlight and is not toxic to humans. Rinse tomatoes before eating, as you would with any produce. Follow the label's harvest waiting period, though most Bt products have no waiting period or only 24 hours.

What if I see holes in tomato fruit but no caterpillar?

The caterpillar is likely inside the fruit. Fruitworms burrow into tomatoes to feed. Remove and discard affected fruit to prevent the caterpillar from completing its life cycle. Spray Bt on the plant to prevent new infestations.

Can I use dish soap to make my own insecticidal spray?

Diluted dish soap can work on very young caterpillars, but commercial insecticidal soap is formulated to stick to leaves and is more effective. Homemade soap spray may also damage plant leaves if the concentration is too strong. Commercial products are inexpensive and more reliable.