Hornworm caterpillars (Manduca quinquemaculata), also referred to as tomato hornworms, can devastate tomato plant foliage and fruit in the summer months. Hornworm caterpillars are identified by eight V-shaped markings on their body and a prominent horn in the rear. It’s imperative to eradicate a hornworm infestation as soon as possible to stem the damage and prevent future infestations. There are several methods you can employ to get rid of caterpillars on your tomato plants, including cultural, chemical, physical and biological.

Hornworm caterpillars have a natural camouflage that deters predators.
Hornworm caterpillars have a natural camouflage that deters predators.

Step 1

Inspect your tomato plants two times a week in the summer for signs of caterpillar infestation. Signs include unnatural defoliation, fruit damage and small holes near the fruit stems. Look carefully for the caterpillars themselves, as they blend with the leaves.

Step 2

Remove caterpillars from the plants by hand and destroy them by placing them in soapy water.

Step 3

Till your garden after each harvest with a tiller, working your way down the soil in rows. Till each row only once. Tilling eliminates burrowed caterpillars and caterpillar pupae.

Step 4

Plant spearmint, clover or daisies in proximity to your tomato plants to attract paper wasps, a natural predator of the horned caterpillar. Paper wasps rarely have stingers and are attracted to the insects. The small Braconid wasp also gravitates to the aforementioned plants. Braconids seldom have stingers and feed on the caterpillars until pupation and kill them before seeking other prey.

Step 5

Apply insecticidal soap or an insecticide containing one of the following active ingredients: bacillus thuringiensis, permethrin, bifenthrin, carbaryl or spinosad. Follow the manufacturer’s instructions when using an insecticide regimen. Of the previously mentioned insecticides, bacillus thuringiensis kurstaki is naturally occurring and specific to caterpillars.

Things You Will Need

  • Soapy water
  • Garden tiller
  • Spearmint, clover or daisies
  • Insecticidal soap or insecticide

Tip

  • Transplant your tomato plants to a different area of your garden each year after an infestation to prevent caterpillars burrowed in the soil from feeding.
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