Sub-Lethal and Transgenerational Effects of Nucleopolyhedrovirus on Helicoverpa armigera and Its Synergistic Potential with Biorational Insecticides for Effective Pest Management

Abstract The tomato fruit borer, Helicoverpa armigera (Hubner) (Lepidoptera: Noctuidae), is a highly adaptable, polyphagous insect pest known for causing extensive damage to a wide range of crops across the globe. This study aimed to assess the impact of sub-lethal doses of Helicoverpa armigera nucleopolyhedrovirus (HearNPV) on both treated parental populations and their F1 progeny, and to evaluate the efficacy of HearNPV when combined with half the recommended doses of Emamectin benzoate and Spinetoram. The objective was to enhance pest management efficacy while reducing insecticide usage against H. armigera. Sub-lethal doses of HearNPV significantly increased the pupal, incubation, and ovipositional periods, while causing notable reductions in pupation rate, adult emergence, fecundity, egg hatchability, and adult longevity in both male and female moths. Transgenerational effects were evident, as viral transmission to offspring negatively impacted F1 development and reproduction, although to a lesser extent than in the treated parental generation. Under field conditions in tomato crops, the combination of HearNPV with Spinetoram resulted in the highest larval mortality (92.18%), followed by HearNPV + Emamectin benzoate (87.82%), Spinetoram alone (71.13%), Emamectin benzoate alone (69.52%), and HearNPV alone (66.49%). These findings highlight the potential of HearNPV to induce both sub-lethal and transgenerational effects, significantly contributing to population suppression of H. armigera, and demonstrate that its combined use with reduced insecticide doses is an effective integrated pest management strategy.