Toxicity and Biological Effects of Beauveria brongniartii Fe(0) Nanoparticles against Spodoptera litura (Fabricius)

SIMPLE SUMMARY: Metal-based nanoparticles of different microbial pest control agents have been effective against several pests. This study reports the synthesis of Beauveria brongniartii based Fe(0) nanoparticles (Fe(0)NPs) and their bio-efficacy against Spodoptera litura that was observed during this study. The median lethal concentration (LC(50)) of Fe(0)NPs against S. litura after 7 days was 59 ppm, whereas the median survival time (LT(50)) for 500 ppm concentrations of Fe(0)NPs was 2.93 days. B. brongniartii Fe(0)NPs caused a significant reduction in feeding and growth parameters as well as detoxifying enzyme production by S. litura at the end of the experimental period. These findings suggest that B. brongniartii Fe(0)NPs can potentially be used in environmentally friendly S. litura management programs. ABSTRACT: Nanotechnology has clear potential in the development of innovative insecticidal products for the biorational management of major insect pests. Metal-based nanoparticles of different microbial pest control agents have been effective against several pests. Synthesis of Beauveria brongniartii based Fe(0) nanoparticles (Fe(0)NPs) and their bio-efficacy against Spodoptera litura was observed during this study. Beauveria brongniartii conidia were coated with Fe(0)NPs and characterized by applying a selection of different analytical techniques. Ultraviolet (UV) spectroscopy showed the characteristic band of surface plasmon at 430 nm; Scanning electron microscopy (SEM) images showed spherical shaped nanoparticles with a size ranging between 0.41 to 0.80 µm; Energy-dispersive X-ray (EDX) spectral analysis revealed characteristic Fe peaks at 6.5 and 7.1 Kev; the X-ray diffractogram showed three strong peaks at 2θ values of 45.72°, 64.47°, and 84.05°. The bioassay studies demonstrated that mortality of 2nd instar S. litura larvae following Fe(0)NPs treatment increased with increasing concentrations of Fe(0)NPs at different time intervals. The median lethal concentration (LC(50)) values of Fe(0)NPs against S. litura after seven days of fungal treatment was 59 ppm, whereas median survival time (LT(50)) values for 200 and 500 ppm concentrations of Fe(0)NPs against S. litura seven days post-treatment were 5.1 and 2.29 days, respectively. Beauveria brongniartii-Fe(0)NPs caused significant reductions in feeding and growth parameters (relative growth rate, relative consumption rate, and efficiency of conversion of ingested food) of S. litura. Beauveria brongniartii Fe(0)NPs induced reduction in glutathione-S-transferase activities throughout the infection period whereas activities of antioxidant enzymes decreased during later periods of infection. These findings suggest that B. brongniartii Fe(0)NPs can potentially be used in biorational S. litura management programs.