Resistance development in pink bollworm (Pectinophora Gossypiella Saunders) against Bt cotton and its' establishment as mid season pest in India.

The pink boll worm now became a menace for sustainable cultivation of Bt cotton in India. Based on the data recorded in unsprayed conditions at 13 different locations of north, central and south cotton growing zone between 2007 and 2023, initiation of green boll damage during later part of the season was observed on Bt cotton genotype during 2009-2014 wherein incidence of PBW already existed on non-Bt genotype. In our research, between 2014 and 2017, the central and southern regions of India experienced a rise in the survival of pink bollworms on Bt cotton surpassing the Economic Threshold Level (ETL) whereas in the north zone PBW incidence started in 2018 at experimental locations. The data validate the initial success of Bt/BG-II cotton in its first ten years (2002-2013) of introduction including pink bollworm, which caused negligible green boll damage (0-1.03%) on Bt/BG-II genotypes, while the incidence on non-Bt genotypes was much higher (2.5-23.01%). Following that, an establishment phase was detected in 2014, confirmed by the equal presence of pink boll worm in BG-II and non-Bt, with minimal infestation differences in BG-II and non-Bt, indicating a larger presence of resistant individuals. Following 2014, the coexistence of PBW in BG-II and non-Bt populations was noted concurrently, with a gradual increase in incidence over ETL beginning in the middle of the season. Farmer's field surveys reported highest number of locations above ETL during 2017 with a decreasing trend both in central and south zone. In the north, infestations were low until 2021, but increased significantly, reaching their highest point in 2023. The emergence and spread of PBW resistance to Bt cotton, facilitated by off-season survival and carryover, poses a substantial threat to the sustainability of BG-II cotton cultivation in India.