Identify the caterpillars eating your tomatoes

The caterpillars most likely to damage your tomato plants are the tomato hornworm and the fruitworm (also called the corn earworm). Hornworms are large green caterpillars, up to 4 inches long, with white stripes and a horn-like projection on the rear end. Fruitworms are smaller, about 1 inch long, and range from green to brown to pink, with thin stripes running lengthwise. Both eat leaves, stems, and fruit.

You can spot damage by looking for dark droppings on leaves below the feeding area—this is caterpillar frass, and it's often the first sign of an infestation. Hornworms leave large, ragged holes in leaves. Fruitworms bore into the fruit itself, creating small entry holes and tunnels inside. Check your plants every few days during the growing season, especially in early morning when caterpillars are most active.

Key Takeaways

  • Handpick large caterpillars like hornworms in early morning or evening, when they are easiest to spot and remove.
  • Spray Bacillus thuringiensis (Bt) on leaves and fruit every 7 to 10 days to kill small caterpillars before they cause serious damage.
  • Plant companion plants like basil, marigold, and borage near tomatoes to attract natural predators that feed on caterpillar eggs and young caterpillars.
  • Use row covers or netting over young plants to block adult moths from laying eggs on your tomatoes in the first place.
  • Remove plant debris and fallen fruit at the end of the season to eliminate places where caterpillars pupate and overwinter.

Handpick large caterpillars by sight

Handpicking works best for hornworms because they are large and straightforward to spot. Check your plants in early morning or at dusk, when caterpillars feed most actively. Look under leaves, along stems, and inside the fruit cluster. Wear gloves if you prefer—the caterpillars are harmless to humans, though some people find them unpleasant to touch.

Drop caterpillars into a bucket of soapy water to kill them, or place them in a sealed bag and dispose of them in the trash. If you see a hornworm with white cocoons attached to its back, leave it alone—those cocoons are parasitic wasp pupae, and the wasps will hatch and kill other caterpillars in your garden. One hornworm with parasites can prevent future infestations in a small garden.

Spray Bacillus thuringiensis for small caterpillars

Bacillus thuringiensis, or Bt, is a naturally occurring soil bacterium that kills caterpillars but is safe for humans, pets, and beneficial insects. It works only on caterpillars—it does not harm adult insects, birds, or earthworms. Bt is sold under brand names like Monterey Garden Insect Spray and Safer Brand, available at most garden centers and online.

Mix and spray Bt according to the label directions, coating the tops and undersides of leaves and all exposed fruit. Spray in early morning or late evening when caterpillars are feeding and when beneficial insects like bees are less active. Reapply every 7 to 10 days or after rain, and continue spraying until you see no new damage for two weeks. Bt works best on young caterpillars—once they are larger than 1 inch, they are harder to kill.

Use row covers to block egg-laying moths

Row covers are lightweight fabric sheets that let light and water through but block insects. Drape them over young tomato plants at planting time, before adult moths arrive to lay eggs. find the edges with soil, rocks, or garden staples so moths cannot slip underneath. Remove the covers once plants flower and need pollinator access—usually 4 to 6 weeks after planting, depending on your climate.

Row covers prevent the problem before it starts, which is more effective than treating caterpillars after they hatch. They also protect against other pests like flea beetles and spider mites. The downside is that you must remove them during flowering, so this method works best as a preventive step for young plants rather than a season-long solution.

Plant companion plants to attract natural predators

Parasitic wasps, tachinid flies, and ground beetles all hunt caterpillar eggs and young caterpillars. You can attract these predators by planting flowers and herbs near your tomatoes. Basil repels some adult moths while also attracting beneficial insects. Marigolds, borage, dill, and fennel are excellent at drawing in parasitic wasps. Plant these in clusters near your tomato bed, or intersperse them throughout the garden.

Let some of these plants flower and go to seed—the pollen and nectar feed the beneficial insects, and the seeds feed birds that also eat caterpillars. This approach takes time to build up a population of predators, so it works best as a long-term prevention strategy combined with other methods during the current season.

Remove plant debris and fallen fruit

At the end of the growing season, caterpillars pupate in soil and plant material, then emerge as moths the following spring. Remove all dead leaves, stems, and fallen fruit from around your tomato plants and dispose of them in the trash or a hot compost pile (above 140°F). Till the soil around the base of plants to expose pupae to predators and weather.

Do not leave tomato plants standing in the garden over winter. Pull them out completely, including roots, and clean up the area. This single step reduces the number of caterpillars that survive to the next season and makes spring infestations much lighter. If you compost plant material, make sure your pile reaches and maintains a temperature of at least 140°F for several days to kill pupae.

Rotate crops and avoid planting in the same spot

Caterpillars that pupate in soil near your tomato plants will emerge as moths in the same location the following year. Plant tomatoes in a different bed each season, at least 20 feet away from where you grew them before. This breaks the cycle because the moths will emerge in an empty area and have to travel farther to find food.

If your garden space is limited, plant non-host crops like beans, lettuce, or carrots in the tomato bed the following year. Hornworms and fruitworms feed on tomatoes, peppers, and eggplants—they will not lay eggs on other vegetables. Rotating crops is one of the most reliable long-term ways to keep caterpillar populations low without spraying every week.

Frequently Asked Questions

Can I use neem oil to kill caterpillars on tomatoes?

Neem oil is less effective on caterpillars than Bt because it works by disrupting insect feeding and reproduction rather than killing them outright. It may slow caterpillar growth but will not stop damage quickly. Bt is the better choice for active infestations. Neem oil works better on soft-bodied insects like aphids and spider mites.

Is it safe to eat tomatoes after spraying Bt?

Yes. Bt breaks down in sunlight and is not toxic to humans or animals. You can harvest and eat tomatoes when ready after spraying, though rinsing them first is always a good practice. Follow the label directions for the specific product you use, as some brands recommend waiting a certain number of days before harvest.

What if I see holes in the fruit but no caterpillar inside?

The caterpillar has likely already moved to another fruit or pupated in the soil. Remove the damaged fruit and dispose of it in the trash to prevent the caterpillar from completing its life cycle. Continue scouting for caterpillars on other parts of the plant and spray Bt if you find more damage appearing.

Do I need to use pesticides, or can I rely only on handpicking?

Handpicking alone works if you check plants daily and catch caterpillars when they are small. However, it requires consistent effort and is straightforward to miss caterpillars hiding inside the fruit or deep in the foliage. Combining handpicking with Bt or row covers gives you better control with less time spent searching.