Bt Research 2025, Vol.16, No.6, 259-268 http://microbescipublisher.com/index.php/bt 264 the use of pesticides decreased, the output increased, and farmers' income rose accordingly. The profits of small-scale farmers even rose by 50%, and the lives of many families improved as a result (Kranthi and Stone, 2020). But the good times did not last forever. A few years later, problems gradually emerged - pests like the pink bollworm began to develop resistance to Bt, while the number of some non-target pests that were not major issues before increased significantly. As a result, the use of pesticides has returned and even exceeded that before (Tabashnik and Carriere, 2019; Peshin et al., 2021). Ultimately, Bt cotton still plays a significant role in India, but its benefits are also clearly challenged by resistance issues and changes in pest structure. 5.2 Performance of Bt maize in the U.S.: pest control, policy support, and business models Bt corn in the United States has taken a different path. Since the mid-1990s, Bt corn has been rapidly promoted. This is not only due to the technology itself, but also a complete set of policy support behind it. For instance, the high-dose/refuge zone strategy requires farmers to grow a portion of non-genetically modified crops to slow down the emergence of resistance. This method was quite effective in the past. The European corn borer and cotton bollworm remained sensitive to Bt for more than ten years (Wang et al., 2025). However, the situation has changed in recent years. Resistance has begun to rise. Corn bores in some areas are no longer so "obedient", forcing regulatory authorities to promote multi-toxin technology, strengthen the management of refuge areas, and even encourage the cultivation of non-BT corn for crop rotation (Figure 2) (Arends et al., 2021). It can be said that the "combination punch" of the United States in promoting Bt crops - including the linkage of regulation, research and commercial interests - has indeed enabled this technology to go further, but it is now also facing new pressures. Figure 2 Predicted survival of H. zea larvae in response to proportional areas of cotton at six levels of proportional abundance of maize during the prior year within a 1-km radius of the collection site (Adopted from Arends et al., 2021)
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