Bt maize has provided effective control of major lepidopteran pests for more than two decades, yet the evolution of resistance continues to shape the long-term durability of these technologies. This seminar presents a comparative case study of two major maize pests, the European corn borer (ECB, Ostrinia nubilalis) and the southwestern corn borer (SWCB, Diatraea grandiosella), that were exposed to the same Bt traits but followed markedly different resistance trajectories.
Drawing on more than a decade of laboratory bioassays, field collections, mechanistic studies, and large-scale sentinel plot monitoring, I examine how resistance to Cry1F emerged in isolated regions of North America and how subsequent outcomes diverged between species. In ECB, Cry1F resistance was recessive, no functionally relevant cross resistance to Cry1Ab was observed, and Cry1Ab based pyramids have remained effective in the field in Maritime Canada. In contrast, SWCB populations in parts of the US Southwest evolved resistance to both Cry1F and Cry1Ab, ultimately necessitating a shift to Vip3Aa based pyramids to maintain effective control. Together, these case studies illustrate how pest biology, resistance mechanisms, and regional selection pressures interact to shape durability outcomes and underscore the importance of continuous, region-specific monitoring to inform resistance management and trait deployment strategies.
Dr. Amit Sethi