Indiscriminate and unregulated application of pesticides produces deleterious effect in various groups of organisms including humans and the environment. To solve these issues, it has been reported that the residue-free green nanocomposite synergistically enhances the pesticide efficacy. In this study, ZnO nanoparticles (NPs) with a thiamethoxam nanocomposite were synthesized and we investigated their synergistic effect on 4th instar larvae of Spodoptera litura (Lepidoptera: Noctuidae). These larvae were allowed to feed on the composite of ZnO NPs with thiamethoxam (10-90 mg/L) and thiamethoxam-impregnated castor leaves. Observations showed an increased larval mortality (27% increased mortality), a malformation in pupae and adults, overdue emergence, and reduced fecundity and fertility. A significant dose-dependent variation in the biochemical parameters such as superoxide dismutase (SOD), glutathione-S-transferase (GST), and thiobarbituric acid-reactive substances (TBARS) in the treated larvae was also observed. A decline of 72.42 and 33.82% in SOD and GST activity ,respectively, was observed at higher concentration as compared to the control. On the contrary, it enhanced the TBARS level up to 56.7%. The synthesized nanocomposite was characterized by different biophysical techniques such as X-ray diffraction (average crystalline size 34 nm), scanning electron microscopy, transmission electron microscopy (average particle size 30 nm), and Fourier transform infrared spectroscopy (Zn-O stretching peaks at 432 cm-1 and 503 cm-1). The observation of the present study suggests that ZnO NPs pave the way for developing cost-effective, eco-friendly, and capable nanomaterial for its applications in the field of biological sciences.
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