Pest of the Week: Tobacco and Tomato Hornworms

Figure 1 Tobacco hornworm larva
Courtesy of University of Kentucky

Figure 2 Parasitized larva
Courtesy Clemson University - USDA Cooperative
Extension Slide Series, www.insectimages.org


Figure 3 Tomato hornworm larva
Courtesy of Colorado State University

Common name: Tobacco and Tomato Hornworms

Latin Name: Manduca sexta (Linneaus), Manduca quinquemaculata

Life Cycle: Two or more generations per year in warmer climates, one generation per year in cooler climates (check local extension information for specifics on life cycles by region); adult moths lay eggs mostly on undersides of leaves, eggs hatch within about five days, larvae generally move through five instars to reach full size, overwinter as pupae in the soil and emerge in the spring as adults who then mate and begin the process again.

Plants effected: Tomatoes, peppers, tobacco, other Solonaceous crops and weed species.

Insect Habit: Adults emerge in spring (first generation) or summer (second and subsequent generations, depending upon climate) to mate and feed on the nectar of deep throated flowers; larvae feed upon foliage of Solonaceous crops and weeds. As larvae mature, large frass is produced and quite evident under and around effected plants even though the actual pest may not be observed. Tobacco hornworm has seven white lines on both sides and curved red horn on last body segment, tomato hornworm has v-shaped white lines on both sides and a straighter, blue-black horn.
Control: Remove larvae as they are found, till soil just after crops are finished for the season (very effective in ridding the soil of overwintering pupae), natural populations of paper wasps and yellowjackets will kill and feed larvae to their larvae, lady beetles and green lacewings will eat eggs1, larvae of the Cotesia congregatus wasp will parasitize hornworm larvae and, if found, should be left alone to complete their life cycle to build up natural enemy populations1 (Fig. 2), Bt products are effective against smaller larval stages.