Molecular Entomology 2024, Vol.15, No.5, 200-208 http://emtoscipublisher.com/index.php/me 202 the cotton season and destroying crop residues have become essential to mitigate resistance development (Edpuganti, 2018). Additionally, strategies like hybridizing Bt with non-Bt cotton have shown potential to counter resistance by preserving susceptible insect populations (Wan et al., 2017). 3.3 Benefits of genetically modified crops in reducing pesticide use The adoption of Bt cotton has led to a substantial reduction in pesticide use. For example, in Ghana, Bt cotton varieties significantly decreased bollworm densities, resulting in lower pesticide application and higher net profits compared to conventional cotton farming (Abudulai et al., 2018). Similarly, in India, Bt cotton reduced pesticide consumption by 28%, while simultaneously increasing productivity by 34% and profitability by 98% (Narayanamoorthy et al., 2020). 3.4 Comparison with conventional control methods In comparison to conventional methods, such as chemical insecticides, Bt cotton offers a more sustainable and environmentally friendly solution for managing cotton bollworms. While chemical control relies on repeated applications of insecticides that can harm non-target organisms and lead to pest resistance, Bt cotton reduces these risks. For instance, in Mexico, Bt cotton has significantly reduced the application of chemical insecticides, contributing to environmental benefits such as the reduction in primary pest populations and minimal impact on non-target species (Rocha-Munive et al., 2018). However, the need for integrated pest management (IPM) strategies remains critical to ensure the long-term effectiveness of Bt cotton and to manage the risks of resistance. 4 Case Study: Management of Cotton Bollworms in Bt Cotton Fields 4.1 Location and background information This case study examines cotton bollworm management in the Saurashtra region of Gujarat, India. Bt cotton, particularly Bollgard II® varieties, has been widely adopted in this region since the mid-2000s. However, starting in 2015, farmers reported high levels of pink bollworm (Pectinophora gossypiella) infestations, leading to severe crop losses. The return of this pest is attributed to the development of resistance to Cry1Ac and Cry2Ab proteins, which are integral to Bt cotton's insecticidal capabilities (Mohan and Komarlingam, 2017). 4.2 Implementation of Bt cotton in the region Bt cotton was introduced in Gujarat in the early 2000s, significantly reducing the use of chemical insecticides and increasing cotton yields. The Bollgard II® technology, which produces two Bt proteins (Cry1Ac and Cry2Ab), became the dominant variety in the region. Farmers quickly adopted the technology, relying on its effectiveness in controlling bollworms and other lepidopteran pests. However, by 2015, pink bollworm populations exhibited resistance to these Bt toxins, particularly in the western cotton-growing states of Gujarat, Madhya Pradesh, and Maharashtra (Naik et al., 2018). This led to widespread crop damage and necessitated new management strategies. 4.3 Monitoring and management practices Following the reemergence of pink bollworm, an area-wide Integrated Pest Management (IPM) approach was implemented. Key strategies included pheromone-based monitoring, which utilized gossyplure-baited traps to track moth populations, and targeted insecticide applications based on trap data. In fields where infestations were detected early, foliar sprays of chemical insecticides were used to supplement Bt cotton’s defenses. This strategy successfully reduced the number of larvae and decreased boll damage rates. The integration of pheromone traps and targeted chemical applications demonstrated improved control over relying solely on Bt cotton (Carrière et al., 2017). Furthermore, efforts were made to increase compliance with refuge planting-growing non-Bt cotton alongside Bt cotton to slow the evolution of resistance. However, the effectiveness of this approach was limited due to poor adoption of refuges by farmers. To address the resistance issue more effectively, additional management tactics were introduced, such as shorter cotton seasons and destruction of crop residues to prevent pest overwintering (Tabashnik and Carrière, 2019).
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