Dynamics of cry toxin expression levels and pheromone trap catches of pink bollworm, Pectinophora gossypiella (Saunders) in Bt cotton

Pink bollworm (PBW) poses a significant threat to cotton cultivation, particularly in the context of Bacillus thuringiensis (Bt) cotton, where resistance to Bt cotton has led to outbreaks of PBW in various regions across India. An experiment was conducted at the Agriculture Research Station (ARS) in Dharwad during 2021 to 2022 Rabi, aimed to elucidate the relationship between PBW moth activity and meteorological factors, along with Cry toxin expression in different parts of the cotton plant. Cry1Ac toxin levels were measured in different parts of plant, indicating higher concentrations in leaves followed by squares, seed bits and boll rind. The peak was recorded at 80 Days after sowing (DAS), gradually decreasing at 100, 120 and 140 DAS. The decreasing trend in toxin content over time indicates a dynamic regulation of Cry1Ac toxin expression in both leaf and reproductive organs in Bt cotton. Despite the impact of Cry1Ac toxin on PBW, challenges persisted due to the increased pest pressure around 90 DAS as Cry toxin levels had diminished. Field experiments unveiled two distinct peaks i.e., 49th and 50th Standard Meteorological week (SMW) in moth activity coinciding with specific weather conditions after 140 DAS, with a negative correlation observed between moth catches and maximum and minimum temperatures. Notably, no significant negative correlation was found with humidity and rainfall. The observed relationships between Cry toxin levels, PBW population, and meteorological factors underscore the need for an integrated pest management (IPM) approach in Bt cotton cultivation. IPM strategies that consider the complex interactions between the crop, pest, and environmental factors can help optimize pest control and ensure sustainable crop production.