Field Crop 2024, Vol.7, No.5, 270-277 http://cropscipublisher.com/index.php/fc 273 mix strategies in China has also been effective in managing resistance without any reported failures in lepidopteran pest control. However, these strategies require high compliance from farmers, which can be variable and challenging to enforce (Tabashnik et al., 2010). Additionally, the effectiveness of natural refuges can be influenced by the local abundance of non-Bt crops, as seen in the case of Helicoverpa zea in the United States. IPM practices offer a holistic approach to pest management, but their success depends on the integration and proper implementation of various control methods. Despite these challenges, the continuous improvement and adaptation of these strategies are crucial for the sustainable management of pest resistance in Bt cotton. Figure 2 Major Bt cotton planted (A, B) and field monitoring of Pectinophora gossypiella Cry1Ac resistance (C,D) in China (Adopted from Quan and Wu, 2023) Image caption: LC50 represents the median lethal concentration of the Cry1Ac protein to the collected larvae, and error bars stand for the 95% fiducial limits (Adopted from Quan and Wu, 2023) 5 Case Study 5.1 Overview of a specific case study highlighting Bt cotton resistance management This case study focuses on the successful resistance management of Bt cotton in the southwestern United States, where a comprehensive strategy was implemented to combat the pink bollworm (Pectinophora gossypiella). This pest had developed resistance to Bt cotton, posing a significant threat to cotton production in the region. 5.2 Background of the region or field chosen for the case study The southwestern United States, particularly Arizona, has been a major cotton-producing region. The introduction of Bt cotton in the mid-1990s provided an effective means to control the pink bollworm, a major pest in this area. However, by the early 2000s, there were growing concerns about the pest developing resistance to the Bt toxin, which could undermine the benefits of this genetically engineered crop (Tabashnik and Carrière, 2019). 5.3 Description of the resistance problem and strategies implemented to address it The resistance problem emerged as pink bollworm populations began to show reduced susceptibility to the Bt toxin Cry1Ac. To address this, a multi-faceted resistance management strategy was implemented. This included the planting of non-Bt cotton refuges to maintain a population of susceptible pests, mass releases of sterile pink bollworm moths to reduce the pest population, and the use of integrated pest management (IPM) practices. These IPM practices included crop rotation, destruction of crop residues, and the use of additional insecticides when necessary (Knight et al., 2021). 5.4 Outcomes of the resistance management strategy and lessons learned The outcomes of this comprehensive resistance management strategy were highly successful. By 2005, the pink
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