Enhanced Efficacy of Helicoverpa armigera Nucleopolyhedrovirus Against Spodoptera litura Larvae Using Zeolite and Chitosan Nanoparticle Formulations

Helicoverpa armigera Nucleopolyhedrovirus (HearNPV1) shows considerable potential as a sustainable biological control agent against insect pests. Enhancing its efficacy through formulation with appropriate carrier materials is critical for improving pest management strategies. This study evaluated the potential of chitosan and zeolite nanoparticles as delivery vehicles for HearNPV1, assessing their effects on mortality and lethal time in second-instar Spodoptera litura larvae. A single-factor randomized block design with three replications was used. The treatments consisted of HearNPV1 formulated with various concentrations (0.125% to 0.5%) of either chitosan or zeolite nanoparticles. Larval mortality and lethal time (LT) were recorded and analyzed using one-way ANOVA, with significant differences further assessed by Duncan's multiple range test (α=0.05). Results showed that formulating HearNPV1 with either chitosan or zeolite nanoparticles significantly increased larval mortality. Notably, even the lowest concentration tested (0.125%) of both chitosan and zeolite nanoparticles achieved 66.67% larval mortality within seven days post-infection. However, no significant differences in lethal time were observed among treatments, regardless of nanoparticle type or concentration. Larvae exposed to virus-nanoparticle formulations exhibited lethal times ranging from 3.0 to 4.67 days on average-similar to the duration observed in larvae infected with HearNPV1 alone. In conclusion, both chitosan and zeolite nanoparticles at 0.125% concentrations effectively enhanced HearNPV1-induced mortality in S. litura larvae, although they did not shorten the time to death. These findings underscore the potential for nanoparticle-based HearNPV1 formulations to improve biological pest control, warranting further investigation into their practical application and mechanisms of action.