Bt resistance in a billion-dollar bug, European corn borer in Minnesota and Wisconsin

The European corn borer (ECB), Ostrinia nubilalis (Hübner), is a significant pest of corn, causing over $1 billion in annual economic losses before the introduction of Bt technology. Since 1996, the widespread adoption of Bt corn has significantly suppressed ECB populations. However, after > 29 years, the benefits of Bt corn for managing ECB are under serious threat due to the evolution of resistance, with resistant ECB populations documented across Canada and in Connecticut in recent years. Currently, two key insect resistance management (IRM) strategies, high dose/refuge and gene-pyramiding, are used to delay insect resistance. For these strategies to remain effective, it is crucial to understand the Bt resistance allele frequencies in the field, inheritance patterns, fitness costs, and cross-resistance. In this study, we conducted F2 screens of ECB against Cry1Ab, Cry1F, Cry1A.105 and Cry2Ab2 proteins with populations collected from Wisconsin and Minnesota during 2023-2024; characterized the inheritance of Cry2Ab2 resistance in multiple ECB populations; assessed the fitness costs associated with the Cry2Ab2 resistance; and evaluated the cross-resistance patterns between Cry2Ab2 resistance and Cry1 Bt proteins. Data for this research are foundational to IRM and pest control, supporting the sustainable use of Bt technology for ECB control.