Bt Research 2025, Vol.16, No.5, 204-213 http://microbescipublisher.com/index.php/bt 211 7.2 Long-term ecological effects of inhibiting pest resistance The evolution of drug resistance is a serious challenge in pest management, and the comprehensive use of multiple biological control methods is considered an effective way to delay the development of pest resistance. Multifactorial action reduces the chances of individual pests to survive, and from an evolutionary perspective, it reduces the space for accumulation of adaptive variants such as resistance. Under the Bt crop-natural enemy combination system, a considerable number of anti-Bt individuals remaining in the field will be preyed or parasitized by natural enemies, thus unable to spread resistance genes across generations. A study based on model and field validation showed that in Bt cotton fields with abundant predatory natural enemies, the frequency of resistance genes of cotton bollworms to Bt increased significantly slower than in environments lacking natural enemies (Chen and Shelton, 2011; Liu et al., 2014). Comprehensive strategies often involve different modes of action, which forces pests to simultaneously adapt to multiple selection pressures and are less likely to evolve broad-spectrum resistance. For example, when facing Bt toxin and fungal infections at the same time, if the pest resists Bt through the midgut mutation, it may still die due to fungi penetrating the epidermis; on the contrary, even if some pests are tolerant to fungi, they still cannot escape poisoning when feeding Bt plants. 7.3 Research on field ecosystem balance for Bt integration application The IPM strategy of Bt combined with a variety of biological control measures is widely adopted, not only focusing on the effects of pest control, but also emphasizing the maintenance of the overall balance and health of the field ecosystem. Research shows that in farmlands that have long implemented the "Bt+biological control" strategy, some key indicators of the ecosystem tend to be optimized (Zhang et al., 2018). Taking the Bt cotton planting area in northern China as an example, after large-scale Bt cotton planting combined with natural enemies' protection, the incidence of secondary pests such as aphids and red spiders in cotton fields and surrounding crop fields has decreased significantly, and the total number of pests in the entire farmland ecosystem has decreased, and the number of natural enemies has increased, achieving a new balance. This balance is not only reflected in population size, but also in the functional level. Bt reduces the direct damage to plants by drilling pests and protects the strength of the plant individuals; natural enemies control pests, reducing disease transmission and quality loss; pathogenic microorganisms reduce the wintering base of residual insects. As a result, crops grow well and primary productivity in farmland can be maintained and even improved. In addition, soil ecology may also benefit from reducing inputs in chemical pesticides and alternatives to biological measures. The study found that the number of organic matter decomposition bacteria, earthworms, etc. in the fields that implement Bt comprehensive biodefense is 20%~30% higher than that in conventional pesticide fields, and soil respiration intensity and enzyme activity indicators have also improved. This suggests that integration strategies contribute to the recovery of soil ecological functions and enhance soil’s ability to support plants. Acknowledgments The authors would like to thank all teachers and colleagues who provided guidance and assistance during this research, and for the peer review's revision suggestions. Conflict of Interest Disclosure The authors confirm that the study was conducted without any commercial or financial relationships and could be interpreted as a potential conflict of interest. References Abbas M., 2020, Interactions between Bacillus thuringiensis and entomophagous insects, Egyptian Journal of Biological Pest Control, 13: 913715. https://doi.org/10.1186/s41938-020-00255-8 Abdolmaleki A., Dastjerdi H., Maafi Z., and Naseri B., 2017, Virulence of two entomopathogenic nematodes through their interaction with Beauveria bassiana and Bacillus thuringiensis against Pieris brassicae (Lepidoptera: Pieridae), Journal of Crop Protection, 6: 287-299.
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