Insecticide Resistance in Pink Bollworm, <scp> <i>Pectinophora gossypiella</i> </scp> (Saunders) Across Cotton Growing Regions of India

The pink bollworm (PBW), Pectinophora gossypiella, poses a significant threat to cotton crops, leading to considerable economic damage globally. As the effectiveness of transgenic Bt cotton (BG II) against this pest diminishes, there has been a concerning rise in the use of synthetic insecticides. This study aimed to assess the prevailing levels of insecticide resistance in Indian populations of PBW to commonly recommended insecticides and to investigate the expression of detoxifying enzymes in field populations of PBW exhibiting resistance to insecticides. Ten populations of PBW were collected from major cotton-growing regions of North, Central, and South India. Median lethal concentrations were determined using topical bioassays with five technical-grade insecticides. Most field populations exhibited high resistance to fenvalerate and quinalphos, moderate to high resistance to spinosad and spinetoram, and low to moderate resistance to emamectin benzoate. Overall, populations from Central India exhibited the highest resistance levels, followed by those from North India. Detoxifying enzyme activity was significantly higher in field populations (p < 0.001), with esterases ranging from 84.76 ± 1.91 to 158.92 ± 2.34, glutathione-S-transferase from 15.94 ± 0.96 to 38.89 ± 1.68, and cytochrome P450s from 1.39 ± 0.19 to 5.06 ± 0.22 nmol/min/mg protein, corresponding to increases of 1.02-1.88-fold, 1.09-2.43-fold, and 1.1-3.64-fold, respectively, compared to the susceptible population. These results underscore the need to revise the list of recommended insecticides for PBW management, excluding those to which the pest has developed significant resistance.