Comparative Insecticides Toxicity against Third Instar Spodoptera frugiperda Populations in Southern India

A laboratory bioassay using the topical application method was conducted to determine the relative toxicity of various insecticides against the fall armyworm, Spodoptera frugiperda (J. E. Smith), under controlled conditions at the Department of Entomology, Professor Jayashankar Telangana Agricultural University, Rajendranagar, Hyderabad. The study aimed to evaluate the effectiveness of Chlorantraniliprole 18.5% SC, Emamectin benzoate 5% SG, Spinetoram 11.7% SL, Lambda-cyhalothrin 5% EC and Thiodicarb 75% WP against 3rd instar larvae of S. frugiperda sourced from four regions in South India: Andhra Pradesh, Karnataka, Tamil Nadu, and Telangana. The insecticides were ranked in terms of toxicity (LC50) as follows: Emamectin benzoate (0.99 to 1.02 ppm) > Spinetoram (1.14 to 1.21 ppm) > Chlorantraniliprole (1.5 to 2.14 ppm) > Lambda-cyhalothrin (31.5 to 35.62 ppm) > Thiodicarb (427.36 to 557.37 ppm). Among these, emamectin benzoate was identified as the most toxic, with the lowest LC50 value in Karnataka and Tamil Nadu (0.99 ppm), while Thiodicarb was the least toxic, showing the highest LC50 value in Telangana (557.37 ppm).