Biological implications of field-evolved Cry1F resistance and pheromone race in European corn borer, Ostrinia nubilalis Hübner

Abstract

European corn borer, Ostrinia nubilalis Hübner, is a major corn pest in North America. Ostrinia nubilalis is managed using transgenic corn (Zea mays L.) producing insecticidal toxins from Bacillus thuringiensis Berliner (Bt). Field-evolved resistance to the Cry1F toxin was first discovered in Nova Scotia, Canada, in 2018. Since Bt corn hybrids have successfully managed O. nubilalis for more than 20 years, most available life history information is outdated. The objectives of this thesis were to determine pheromone race of O. nubilalis across Canada, fitness of Cry1F-resistant O. nubilalis, and inheritance of Cry1F resistance. Ostrinia nubilalis across Canada, including Cry1F-resistant strains, are primarily Z-race, indicating mitigation strategies can be focused on corn. No fitness costs were observed in the Cry1F-resistant strain, so Cry1F resistance is likely to persist in the absence of Cry1F. Field-evolved Cry1F-resistance is autosomal recessive, so the high-dose/refuge strategy did not fail due to Cry1F resistance inheritance pattern.