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Be-at-Home with Nature: Tobacco hornworms

[CREDIT: K.Clements]

The very hungry caterpillar

The tobacco hornworm (Manduca sexta) is not a worm. It is a caterpillar, a very hungry caterpillar. They are called hornworms because they have a harmless, red horn on their abdomen. These common garden pests are known for eating entire leaves off of plants from the Solanaceae family, such as tomato, pepper, eggplant, petunia, tobacco, or potato plants. So, if you notice that your tomato or pepper plant is becoming bare, the tobacco hornworm may be the culprit.  

Lifecycle  

[CREDIT: K.Clements]

Tobacco hornworms start their life as eggs underneath a leaf in your garden. Moths lay eggs on the leaves of plants from the Solanaceae family, also known as nightshades.

About five days after being laid, the eggs hatch and become larvae. The larvae then feed on leaves or ripening fruit. Unlike most caterpillars, they consume the entire leaf. At this stage, they grow from around 6 millimeters to 8 centimeters.  

About three weeks later, the larvae become pupae. In this stage, the hornworms drop off the plants to burrow in the soil in a reddish-brown colored cocoon. 

Carolina Sphinx Moth [CREDIT: Lyle Buss, Entomology & Nematology Dept. University of Florida]

One to two weeks later, a beautiful moth emerges. At this point in their life, they are known by the name Carolina Sphinx Moth. They can be identified by their six yellow/ orange markings. The Carolina Sphinx Moth can easily be confused with the Five Spotted Hawk Moth, aka a tomato hornworm, who has five yellow/ orange markings. Tomato hornworms are not as common in the southeastern United States.  

Wild, wacky, and wonderful

Cube shaped frass. [CREDIT: K.Clements]

Cube Shaped Frass: To prevent the tobacco hornworm from taking over your garden, check your leaves for cube shaped droppings. This is a sign that tobacco hornworm larvae are feasting on the leaf above. It is recommended to check for them twice a week in the summer months. Additionally, make sure to remove unnecessary nightshade weeds from your garden. You do not want to provide any extraneous food sources for these hornworms. 

 

Masters of Defoliation: Tobacco hornworms are successful conquerors of many nightshade plants. The hungry hornworm chomps away at both your foliage and your fruit.  Luckily, there are a few ways to free your plant of their rule.

  • Remove the hornworms by hand and kill them by placing them in soapy water. 

    Cotesia congregata larvae on a tobacco hornworm [CREDIT: Pat Morgan from Pixabay]

  • Till your soil to destroy any underground pupae.  
  • Allow Mother Earth to take it into her hands and let natural predators kill off these nightshade-rulers. Wasps, lady beetles, and birds are all enemies of the hornworm. The wasps (Cotesia congregata) are particularly interesting because they lay dozens of eggs in the tobacco hornworm. The larvae then feed on the hornworm, killing it in the process.
  • Pesticides such as insecticidal soap can be your last line of defense in this war against the hornworm. Be sure to follow all safety precautions and instructions on whichever pesticide you choose.  

 

Nocturnal Pollinators: The Carolina Sphinx Moths are nocturnal pollinatorsThey are fast, agile flyers that can hover and dart between flowers like a hummingbird. Even though tobacco hornworms can be a nuisance, their adult form is an essential part of the ecosystem. 

Questions and inquiries 

Make your own egg carton caterpillar!

Materials:

  • Cardboard egg carton
  • Green and white paint
  • Paint brush
  • Scissors
  • Red pipe cleaner
  • Optional: Googly eyes

 

Directions:

  • Cut egg carton in half
  • Paint the entire egg carton light green
  • Paint 7 white, diagonal stripes across the “body” of the caterpillar
  • Paint eyes or glue on googly eyes

    [CREDIT: Kassidy House]

  • On the opposite end from the eyes, use scissors to poke a small hole in the egg carton
  • Glue a red pipe cleaner in the hole and voilá! You made your very own tobacco hornworm!

 

Can you tell the difference between a moth and a butterfly? Click here for the worksheet and here for the answers!

One Comment on “Be-at-Home with Nature: Tobacco hornworms

  1. You may be the first person to have ever written this phrase, “cube shaped droppings”. Congrats!

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