Acute and Persistent Toxicity of Newer Insecticide Molecules Against Invasive Pest of Maize, Fall Armyworm Spodoptera frugiperda (J.E.Smith)

Abstract

Laboratory and pot culture experiments were conducted to assess the acute and persistent toxicity of new molecular insecticides against the notorious invasive pest of maize, Spodoptera frugiperda during 2020- 2021 at Department of Agricultural Entomology, Tamil Nadu Agricultural University, Coimbatore. Results revealed that, the LC50 value of emamectin benzoate, chlorantraniliprole, spinetoram, flubendiamide and novaluron were 0.05, 4.08, 0.1, 85.89 and 0.91 ppm, respectively for second instar larvae and 0.03, 5.63, 0.02, 162.99 and 0.99 ppm for third instar larvae of fall armyworm. Among insecticides tested emamectin benzoate and spinetoram showed high toxicity to S. frugiperda than other insecticides by registering a minimum LC50 value. But in the persistent toxicity studies, the same insecticides showed less persistence on maize crop. Hence, insecticides like flubendiamide and chlorantraniliprole need to be recommended in the early stage of the crop period (within 20 days after sowing) and less persistent insecticides viz., emamectin benzoate and spinetoram should be recommended in the middle stage (25 to 40 days) of the maize crop for the management of S. frugiperda so that the residues may not accumulate in the harvested produce both in the stalk and grain.