author(s)
Namita Soni and Ramesh C Dhiman

abstract
The aim of this study was to evaluate the effect of green synthesized silver nanoparticles using aqueous leaf extract of Ricinus communis (castor plant) on the life cycle Helicoverpa armigera. The synthesized AgNPs were identified using different microscopic techniques: UV-Visible spectroscopy, Scanning electron microscopy (SEM), Energy-disruptive X-ray spectroscopy (EDX) and Transmission electron microscopy (TEM). Insecticidal activity of AgNPs was studied using leaf dipping method. The biochemical studies were analyzed at LC₅₀ of AgNPs using different methods (total carbohydrate using phenol-sulphuric acid reaction of Dubois method, total protein using Bradford method, total lipid using sulfo-phospho vanillin of Knight method and non-specific esterases using Van-Asperan method, respectively). UV-vis spectrophotometer confirmed the spectra at 445 nm of AgNPs. Spherical shaped AgNPs of 8.96 nm size were confirmed by TEM and SEM. EDX spectra confirm the chemical composition AgNPs. Higher mortality was observed in 6^th instar larvae (70-80% at LC₅₀ 175 ppm) than the other instars. The pupa and adult of H. armigera also exhibited toxicity against the AgNPs. Effect of AgNPs treatment was investigated on the midgut of 5^th instar larva of H. armigera using the transmission electron microscope. Accumulation of AgNPs in cell organelles was confirmed by ultra structural studies of insect midgut cell using TEM. The biochemical components of 5^th instar larvae showed that, the amount of total carbohydrate, total protein, total lipid and non-specific esterases were significantly decreased After 24 h treatment at LC₅₀ of AgNPs. Now, we can summarise that, synthesis of AgNPs using R. communis is a green route to control pest population. The synthesized nanoparticles could be used for the improvement of new botanical nano-insecticide or nano-formulation after successful field trials.