![]() 7 After feeding inside the THW host, larvae emerge to form pupae in a white cocoon from which a wasp will emerge. The adult parasitoid lays an average of sixty-five eggs in THW larva, with a range of 5 to 126 eggs. ![]() One of the most common natural enemies is the Braconid wasp parasitoid Cotesia congregata, which has very visible white cocoons on parasitized THW larvae (figure 6). Natural enemies of THW can cause high levels of larval mortality in the field. Please see the Clemson University Pest Management Handbook for up-to-date control options and pesticide recommendations. An infestation level of ten or more larvae per one hundred plants (10%) indicates that the economic threshold has been reached, and an insecticide application is economically justified. Sufficient moisture in the soil is also needed for the plant to absorb the insecticide. Trials at the Clemson University Pee Dee Research and Education Center near Florence, SC, have shown six to eight weeks activity after transplant with either chlorantraniliprole or cyantraniliprole, though residual activity varies with environmental conditions. These insecticides can be used as a tray drench to seedlings in the greenhouse or in transplant water, which allows the roots to absorb the insecticide. The two insecticides chlorantraniliprole and cyantraniliprole belong to the anthranilic diamide class of insecticides and have systemic activity by root uptake against lepidopteran pests. These include several formulations of Bacillus thuringiensis (Bt) (Javelin, DiPel, etc.), chlorantraniliprole (Coragen), cyantraniliprole (Exirel for foliar applications and Verimark for tray drench/transplant water applications), emamectin benzoate (Denim), acephate (Orthene), and spinosad (Blackhawk). ManagementĪlthough THW can cause major yield loss in tobacco, the insect can fortunately be effectively controlled with a range of insecticides. 2 If no control action is taken, THW can completely defoliate a tobacco plant (figure 5). ![]() ![]() 6 As the tobacco plant ages, it becomes more tolerant of THW feeding. 2 Damage by THW leads to weight loss by defoliation, rather than reduced leaf quality. ![]() The THW is a defoliator and typically begins feeding on the upper leaves of a plant. Tobacco hornworm damage to flue-cured tobacco. ![]()
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