In Silico and In Vitro Assessment Based Optimization of Potential Insecticidal Combination Against Fall Armyworm

The fall armyworm Spodoptera frugiperda (J E Smith) is an invasive pest, causing severe economic damage to maize. The present study demonstrates mining of potential insecticidal molecules using in silico analysis and validating through in vitro and pot experiments. Emamectin benzoate and chlorantraniliprole performed best to block acetylcholine esterase with respective binding energies -37.6 and -35.7 KJ/ mol through multiple hydrogen and hydrophobic interactions. Emamectin benzoate showed the strongest binding (ΔG -41 KJ/ mol) followed bychlorantraniliprole (ΔG -34.3 KJ/ mol) to inhibit ryanodine receptors, whereas, chlorantraniliprole showed the strongest binding (ΔG -27.2 KJ/ mol) followed by emamectin benzoate (ΔG -26.3 KJ/ mol) to GABA. In vitro insecticidal activity revealed strong action of chlorantraniliprole (LC₅₀ 0.039 ppm) and emamectin benzoate (LC₅₀ 0.027 ppm), however their combined effect maintaining 0.75-1:0.9-2.5 (%, w/w) was highly promising with LC₅₀ of 0.01 ppm. SBOD-23 formulation consisting of both insecticides at a concentration of 20 times LC₅₀ (ppm) showed the least whorl damage in maize and highest plant weight without any phytotoxicity.