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At this time of year, many gardeners find that their tomato plants have been stripped of foliage. With a closer look, it may be determined that the tobacco hornworm is to blame. The tobacco hornworm caterpillar is light green in color with seven white diagonal stripes down each side of its body and a distinctive red “horn” on its posterior. The tobacco hornworm will reach up to 4½ inches long. It feeds on the foliage of tomato plants but will also feed on other plants in the nightshade family, such as Irish potato, eggplant and peppers. If a heavy infestation develops, the caterpillars may also feed on the surface of developing tomato fruit, leaving large open scars. Fortunately, the tobacco hornworm has many natural enemies, such as the braconid wasp. The braconid wasp parasitizes the hornworm by inserting eggs into its body. The developing larvae then feed on the hornworm. When the larvae pupate, they spin a small white cocoon on the outside of the hornworm’s body. The clusters of small white cocoons are found on the outside of a parasitized hornworm, making the caterpillar more visible in the tomato foliage.
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This information is supplied with the understanding that no discrimination is intended and no endorsement by the Clemson University Cooperative Extension Service is implied. All recommendations are for South Carolina conditions and may not apply to other areas. Use pesticides only according to the directions on the label. All recommendations for pesticide use are for South Carolina only and were legal at the time of publication, but the status of registration and use patterns are subject to change by action of state and federal regulatory agencies. Follow all directions, precautions and restrictions that are listed.