Studies on Comparative Insecticidal Resistance against Fall Armyworm Spodoptera frugiperda J ESmith in Jammu Region

Abstract

newline The invasion of fall armyworm (Spodoptera frugiperda, J.E.Smith) in Jammu poses a significant threat to maize crop due to its rapid spread and high reproductive capacity. This study investigates the susceptibility and resistance of different fall armyworm populations across various districts in Jammu viz., Kathua, Samba, Jammu and Rajouri to selected insecticides. Bioassays were conducted to determine the median lethal concentration (LC50) of chlorpyrifos, cypermethrin, profenofos and lambda-cyhalothrin, revealed varying degrees of resistance. Chlorpyrifos exhibited the highest resistance levels, followed by cypermethrin, profenofosand lambda-cyhalothrin highlighting significant variability in insecticide susceptibility among populations. These investigations showed that fall armyworm population was highly resistant to chlorpyrifos and was less resistant to profenofos. Moreover, differences in LC50 values for given insecticides across populations denoted that Kathua population shows more resistance followed by Samba, Jammu and Rajouri.Furthermore, the toxicity of newer insecticides moleculesviz., emamectin benzoate, spinetoram and flubendiamide was evaluated against fall armyworm larvae. Emamectin benzoate emerged as the most toxic, followed by spinetoram and flubendiamidedemonstrating 31.314 and 4.074- -timeshigher toxicity relative to flubendiamide, respectively. The study also monitored the development of resistance across successive generations to these newer insecticides, indicating a progressive increase in LC50 values over time, the resistance ratio in the 4th generation compared to the 1st generation was 1.304- 1.412- and 1.359-fold among emamectin benzoate, spinetoram and flubendiamide respectively highlighting the cumulative effect of insecticide exposure on resistance levels in fall armyworm larvae. These findings underscore the urgent need for region-specific management strategies to combat resistance effectively and ensure sustainable pest control in maize growing areasof Jammu. Integr