Annual Research & Review in Biology

Cotton, a vital commercial fibre crop, is prone to heavy infestations by insect pests, with bollworms being the most damaging globally. Helicoverpa armigera and other Heliothines have developed significant resistance to conventional insecticides, rendering cotton cultivation uneconomical in many regions by the mid-1990s. The introduction of Bt cotton, expressing Cry1Ac toxins, marked a breakthrough in bollworm management, drastically reducing pesticide usage and increasing yields. However, resistance to Cry toxins, particularly Cry1Ac, emerged over time, as first reported in pink bollworm (Pectinophora gossypiella) in Gujarat, India, by 2010. Factors contributing to resistance include mutations in genes such as PgCad1, ABC transporters, and others. Additionally, declining toxin expression in Bt cotton hybrids and improper pest management practices exacerbate resistance. Integrated pest management strategies, such as timely sowing, field sanitation, pheromone traps, and mating disruption tools, have been recommended to mitigate resistance. Recent data show an increase PBW infestations in North India, which is being driven by factors like shorter cotton seasons and little prior exposure to Bt toxins. Studies focusing on genetic and phenotypic polymorphism in Indian PBW populations have emphasized the need for sustainable resistance management. Adopting dual-toxin Bt cotton (Cry1Ac + Cry2Ab) and stringent IRM strategies remains critical to preserving the efficacy of transgenic technology.