Screening the Larvicidal activity of ZnO, CuO NPs and neem seed oil extract mixtures against the full armyworm Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae)

The fall armyworm, Spodoptera frugiperda, poses a significant threat to over 90 plant species, causing extensive damage by consuming fresh leaves, hindering growth, and ultimately reducing crop yields. Integrated pest management strategies emphasize eco-friendly approaches, minimizing harm to non-target organisms. Among these, biological control methods, including the use of plant extracts and nanoparticles, have shown considerable efficacy in controlling the fall armyworm.Methods: This study assessed the impact of the neem extract, CuO & ZnO nanoparticle mixtures on the biological aspects of Spodoptera frugiperda. Fourth-instar larvae were exposed to fresh castor leaves treated with neem seed oil extract, obtained through Soxhlet extraction from neem seeds, and nanoparticles prepared via direct precipitation.Results: The estimated LC50 values for neem extract + ZnO were 115 ppm & for neem extract + CuO were 98 ppm, and for ZnO + CuO were 93 ppm, using the second instars. All treatments influenced larval and pupal durations, extending them by 15% and 1% with neem extract + CuO & by 24% and 15% with neem extract + ZnO and by 23% and 33% with ZnO + CuO. Adult longevity also affected negatively by 25,34 and 29% with Neem/CuO, Neem/ZnO and ZnO/ CuO mixtures, respectively. Digestive enzymatic activities in the insects were significantly affected following treatment with the LC-values of all treatments