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Tomato Hornworms: Green isn’t always good

July 20, 2011

It’s mid-summer, when hostile green hornworms (manduca quinquemaculata) emerge from their eggs and make a meal of tomato plants.

Hunting down these ugly worms is a tedious job. Their green color makes them nearly impossible to spot. Oftentimes, you’ll find them above black droppings. Hornworms come out of hiding early morning and in the evenings when it’s cool. Although hornworms usually appear in small numbers, one can destroy an entire plant.

As awful as it sounds, the best control for hornworms is to pick them off the plant and chop them up. I hold a small tin can below the hornworm then scrape it off the branch with a trowel so that it falls into the can. I either chop it in half with the trowel or feed it to the chickens. Some people squish them with their shoe but I don’t care to have green flesh (hornworms are green inside and outside) on the soles of my shoes.

  • Hornworms are named for the horn at the rear end.
  • Hornworms are the larval of the Lepidoptera sphingidae also known as the hummingbird moth.
  • Hummingbird moths are grey or brown with yellowish spots. It lays eggs on upper and lower sides of leaves.
  • Hornworm larvae emerge from its egg eating the plant. They eat leaves, small stems, and part (only part) of the fruit.
  • Hornworms can grow four inches long in four weeks.
  • When a tomato hornworm has reached full growth, it drops from the plant and burrows into the soil to pupate.* Two weeks later, moths emerge and begin mating and laying eggs. During their late cycle, the moths overwinter in the soil and emerge to mate in late spring.
  • Hornworms bearing white egg sacs should be left unharmed. The egg sacs are parasitic wasps, Braconid, which will kill undesirable pests in your garden.

*Non-feeding stage between the larva and adult in metamorphosis insects. This happens when the larva undergoes complete transformation within a protective cocoon or hardened case.

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3 comments

  1. I don’t like hornworms. I have one topsy-turvey hanging tomoato plant and have been fortunate not to experience these ugly creatures. bernadine p.s. my tomato plant has produced 3 yummy, sweet tomatoes so far.

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  2. I always find them on my potato vine first! The black droppings on the slate path are always a giveaway. Hopefully that means the marigolds we plant next to the tomatoes are doing their job detouring the pests. However, the girls (our 3 hens) would like me to find a few more of the protein packed delicacies I’m sure 🙂

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  3. I check every morning for hookworms and if there are any I put them in can and feed them to the chickens.

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