Grow It Eat It: Maryland's Food Gardening Network

Tobacco/Tomato Hornworm

Tobacco hornworm - Manduca sexta
Tomato hornworm - Manduca quinquemaculata

(Click on an image to enlarge.)

hornworm adult tobacco hornworm tomato hornworm - Whitney Cranshaw-Bugwood
Adult Tobacco hornworm larva
 Tomato hornworm larva
hornworm parasitized hormworm damage on tomato fruit
Larva-parasitized Damage-fruit

Video: Larva feeding

Double click on video to enlarge.
Appearance Host Plants Monitoring
Life Cycle/Habits Signs/Symptoms Prevention/Control
Appearance Eggs: round yellow/light green to white, laid in hundreds under leaves.
Larvae: first of 5 instars is yellow-white; others are green with final instar (caterpillar) reaching 3-4" inches in length with 7-8 white side-ways Vs on its side, and a black "horn" at the rear (tobacco hornworms have a red "horn"). 
Pupa: 2" long, hard reddish brown case with a distinctive loop attached that encases the mouthparts.
Adult: large 4-5" gray-brown hawk moth. Front wings, much larger than back wings which have black and white uneven bands. Abdomen has 5 orange-yellow spots.
Life Cycle/Habits Day-flying moths emerge over a long period beginning in May from overwintering  pupal cases in the soil. Eggs laid on leaf underside, rarely on top. Larvae feed voraciously on leaves and sometimes fruit. Mature larvae drop to the soil and burrow up to 6" into soil to form pupal case. One to two generations a year.
Host Plants Tomato, eggplant, pepper, potato.
Signs/Symptoms Caterpillar feeding ordinarily begins at the top of the plant.  Damage is usually unnoticed until the final instar when 90% of defoliation occurs. Their feeding makes large gouges in ripe tomatoes (especially during dry weather).
Monitoring Look under leaves for egg clusters. Green larva color is an effective camouflage. Be alert for light feeding at plant tops. Later entire leaves eaten including stems, leaving stubs. Mostly interior leaves eaten (vs. deer that browse on one side of plant.) Dark, BB-sized, cube shape droppings on leaf surface indicate late instar feeding above.
Prevention/Control
  1. Handpick.
  2. Large hornworms are often parasized by wasps. The cocoons of Braconid wasps look like grains of rice attached to the hornworm's back. Do not kill parasitized hornworms. Let the wasp complete its lifecycle on the worm so it can multiply. A parasitized hornworm stops eating and dies.
  3. Spraying water on plants agitates the hornworms and makes them easier to spot.
  4. Hornworms rarely warrant the use of an insecticide.
  5. Tilling garden soil in spring or fall may expose and kill some of the pupae.


Photo Credits:

UGA5304010 (Tomato hornworm larva): Whitney Cranshaw, Colorado State University, Bugwood.org

Adult moth, tobacco hornworm larva: Mike Raupp, UMD

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For more information, contact Jon Traunfeld

Last updated: 02/7/2012