Baseline Susceptibility and Resistance Monitoring for Novaluran 10% EC against Spodoptera frugiperda (J. E. Smith)

A Study was undertaken to assess the susceptibility of fall armyworm (FAW), Spodoptera frugiperda (J. E. Smith) to Novaluran (10% EC) by diet overlay bioassay method. Novaluran 10% EC was tested in vitro against S. frugiperda, obtained from four important Maize-producing tracts in Tamil Nadu. The susceptible population was obtained from FAW laboratory at TNAU which was in the 150th generation and further, reared up to 157th generation. The LC50 and LC95 values of Novaluran 10% EC to the susceptible population decreased from 0.865 to 0.746 ppm and 2.125 to 1.451 ppm, respectively. The susceptibility index of Novaluran was 1.159 and 1.464. The F157 population of S. frugiperda was used to conduct the preliminary discriminating dosage in Novaluran 10% EC and was 0.746 ppm. Resistance monitoring studies of S. frugiperda from Coimbatore, Perambalur, Salem, and Theni districts revealed that the LC50 values of Novaluran 10% EC ranged from 0.792 and 0.930 ppm for Theni and Coimbatore, respectively. Novaluran 10% EC had the highest resistance ratio of 1.246 fold in the Coimbatore field population and the lowest resistance ratio of 1.061 fold in the Theni field population when compared with the TNAU FAW laboratory susceptible population of S. frugiperda.