Connecticut Garden Journal: Tomato Hornworm | Connecticut Public Radio
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Connecticut Garden Journal: Tomato Hornworm

Aug 8, 2019

I remember my first encounter with the tomato hornworm. I came back after being away from my garden for a few days and noticed the tops of my plants were all munched. I naturally blamed the deer, but after further inspection I came face to face with this 4-inch long, green monster. It was happily munching away on the leaves. I swear I could hear it chew.

Tomato hornworms are common in Northern states. The adult is a gray or brown colored hummingbird-like moth with a 4- to 5-inch wingspan. It lays single eggs on the leaves in late spring. They hatch into these well-camouflaged green caterpillars. The caterpillars feed, then drop to the ground to pupate. They'll have a second generation or overwinter in the soil.

Although they're an imposing-looking larvae, the tomato hornworm isn't dangerous to people, even though some people hate how they curl around your fingers when you pick them off plants. They attack, not only tomatoes, but other solanaceous plants, such as eggplant and pepper. To control hornworms, hand pick individuals and drop them in soapy water. For big infestations you can also spray Bacillus thuriengensis or Bt on the plants to kill them. To more easily find them, go out at night with a black night and they will shine for you! Tilling the soil in spring also will kill the pupae in the soil.

If you happen to see white protrusions on the back of your hornworms, leave them. These are cocoons of the braconid wasp. It’s a parasitic wasp that kills the hornworm and, once they hatch, infect more hornworms.