Translocation and persistence of soil applied chlorantraniliprole as a control measure for Chloridea virescens in tobacco plant Nicotiana tabacum

Abstract

Chloridea(Heliothis) virescens (F.) (Lepidoptera: Noctuidae) (tobacco budworm) management in pre-topped tobacco remains a concern for growers. Chlorantraniliprole, an anthranilic diamide insecticide, emerged as an option for C. virescens in early season tobacco because it selectively targets caterpillars, exhibits systemic action, and satisfies reduced risk classification. It is currently recommended for foliar application at threshold; however, because of its systemic action, many growers deploy soil applications at transplant. We conducted a series of experiments to determine the potential efficacy and longevity of soil applications of chlorantraniliprole for use against C. virescens in tobacco. First, tobacco plants were grown in the NCSU Phytotron, a controlled environment facility, and were treated with chlorantraniliprole soil applications either as a soil injection or soil drench at field equivalent rates at transplant. Plants were either watered daily or two times per week. A field experiment was established at two locations where at transplant in furrow and soil drench applications of chlorantraniliprole were compared to foliar applications. In both these experiments, one of the youngest leaves of adequate length on a subset of plants was sampled weeks three through nine after transplant in the phytotron and five through eight after transplant at the field stations. One-half of each leaf was exposed to second instar C. virescens to assess mortality and feeding, and the other half was analyzed for chlorantraniliprole concentration. Mortality differed between treatments in phytotron and field trials after 96 h exposure. Frass production and survivorship increased as plants grew. Phytotron trials demonstrated longer toxicity to C. virescens than field experiments, and chlorantraniliprole concentrations decreased at a slower rate in the Phytotron than in the field. Our field results suggest that soil applications of chlorantraniliprole are not likely to provide acceptable early season C. virescens control in the field.