Status of insecticide resistance and detoxification enzymes activity in pink bollworm, Pectinophora gossypiella (Saunders) populations from India.

The pink bollworm, Pectinophora gossypiella (Saunders), is one of the most destructive pests of cotton, causing substantial yield losses and threatening the long-term sustainability of cotton cultivation in India. The introduction of transgenic Bt cotton expressing Cry1Ac and subsequently stacked Cry1Ac+Cry2Ab toxins initially provided effective control of bollworm infestations. However, over time, pink bollworm has developed significant resistance, not only to Bt toxins but also to several classes of chemical insecticides, posing a major challenge to effective management. Insecticide bioassays conducted across major cotton-growing regions of India revealed a notable increase in LC50 values in field populations compared to the laboratory-susceptible strain, confirming reduced susceptibility and development of resistance. The highest resistance ratios were recorded in Nagpur (Profenophos-4 fold), Adilabad (Chlorantraniliprole-6.81 fold), Sriganganagar (Emamectin benzoate-24.86 fold), Adilabad (Lambda-cyhalothrin-8.09 fold), Sriganganagar (Indoxacarb-2.53 fold) and Bathinda (Spinetoram-15.45 fold). Conversely, the Coimbatore and Surat populations exhibited the lowest resistance across all the tested insecticides. Biochemical assays further indicated the involvement of detoxification enzymes in resistance mechanisms, showing elevated esterase (2.83-5.29 µmol/min/µg protein) and glutathione S-transferase (GST) activities (11.29-21.43 µmol/min/µg protein) compared to the laboratory susceptible strain that recorded value of 2.49 and 2.78 µmol/min/µg protein respectively. These enhanced enzymatic activities align with known metabolic resistance pathways in insects. The findings underscore the urgent need for implementing integrated resistance management (IRM) strategies to sustain cotton productivity and manage further resistance development for long term sustainability.