ARS | Publication request: Understanding successful resistance management: The European corn borer and Bt corn in the United States

Submitted to: GM Crops
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 10, 2012
Publication Date: June 18, 2012
Citation: Siegfried, B.D., Hellmich II, R.L. 2012. Understanding successful resistance management: The European corn borer and Bt corn in the United States. GM Crops. 3(3):184-193.

Interpretive Summary: Nearly a hundred years after the European corn borer was accidently introduced into North America, effective management and area-wide suppression of pest populations has been made possible through the introduction of genetically-engineered Bacillus thuringiensis corn, called Bt corn. Prior to the introduction of this technology, corn borer was difficult to control because larvae often escaped insecticide applications by boring into cornstalks. Bt corn circumvents this behavior by expressing a high dose of Bt toxin throughout the plant. In this review, we describe what has been learned with regard to European corn borer resistance to Bt toxins either through laboratory selection experiments or isolation of resistance from field populations. We also describe the essential components of the high-dose/refuge (HDR) strategy as they relate to corn borer biology and ecology and that have apparently contributed to its success. Also considered is the recent use of pyramided corn that produces two or more Bt proteins with different modes of action targeted for the same insect. For European corn borer resistance management, pyramids open the door to smaller refuges and the possibility of in-field refuges through the use of seed mixtures. Growers will benefit from pyramids and seed mixtures because insect resistance management (IRM) compliance for refuge size and placement will be easier since refuge is literally in the bag. The fate of next generation transgenic products that include stacked and pyramided Bt events targeting multiple pest species may be determined by the weakest link in the hybrid; that is, the pest most likely to evolve resistance. In the Corn Belt this weak link is unlikely to be European corn borer because the assumptions of the HDR strategy appear to be satisfied. Bt corn for corn borer has established a high standard for growers, industry, and regulators because it has been both remarkably effective and durable. This information is helpful to scientists, regulators, and growers interested in prolonging the use of Bt corn by managing insect resistance to this corn.

Technical Abstract: European corn borer, Ostrinia nubilalis Hubner (Lepidoptera: Crambidae) has been a major pest of corn and other crops in North America since its accidental introduction nearly a hundred years ago. Wide adoption of transgenic corn that expresses toxins from Bacillus thuringiensis, referred to as Bt corn, has suppressed corn borer populations and reduced the pest status of this insect in parts of the Corn Belt. Continued suppression of this pest, however, will depend on managing potential resistance to Bt corn, currently through the high-dose refuge (HDR) strategy. In this review, we describe what has been learned with regard to O. nubilalis resistance to Bt toxins either through laboratory selection experiments or isolation of resistance from field populations. We also describe the essential components of the HDR strategy as they relate to O. nubilalis biology and ecology and that have apparently contributed to its success. Additionally, recent developments in insect resistance management (IRM) specific to O. nubilalis that may affect the continued sustainability of this technology are considered.