The evolution of resistance in pests such as the European corn borer will imperil transgenic maize varieties that express insecticidal crystal proteins of Bacillus thuringiensis. Patchworks of treated and untreated fields can delay the evolution of pesticide resistance, but the untreated refuge fields are likely to sustain heavy damage. A strategy that exploits corn borer preferences and movements can eliminate this problem. Computer simulation indicates that this approach can delay the evolution of resistance and reduce insect damage in the untreated fields of a patchwork planting regime.

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The refuge plus high-dose strategy for resistance management assumes that the frequency of resistance alleles is low. We used an F2 screen to estimate the frequency of resistance to transgenic corn that produces Bacillus thuringiensis Berliner Cry1Ab toxin (Bt corn) in an Iowa population of European corn borer, Ostrinia nubilalis (Hu¨ bner). We also proposed a modiÞcation to the statistical analysis of the F2 screen that extends its application for nonuniform prior distributions and for repeated sampling of a single population. Based on a sample of 188 isofemale lines derived from females caught at light traps during the 2nd ßight of 1997, we show with 95% conÞdence that the frequency of resistance to Bt corn was ,3.9 3 1023 in this Iowa population. These results provide weak evidence that the refuge plus high-dose strategy may be effective for managing resistance in O. nubilalis to Bt corn. Partial resistance to Cry1Ab toxin was found commonly. The 95% CI for the frequency of partial resistance were [8.231024, 9.431023] for the Iowa population. Variable costs of the method were $14.90 per isofemale line, which was a reduction of 25% compared with our initial estimate. KeywordsOstrinia nubilalis, F2 screen, transgenic corn, resistance management BioOne sees sustainable scholarly publishing as an inherently collaborative enterprise connecting authors, nonprofit publishers, academic institutions, research libraries, and research funders in the common goal of maximizing access to critical research. BioOne (www.bioone.org) is a nonprofit, online aggregation of core research in the biological, ecological, and environmental sciences. BioOne provides a sustainable online platform for over 170 journals and books published by nonprofit societies, associations, museums, institutions, and presses. Frequency of Resistance to Bacillus thuringiensisYour use of this PDF, the BioOne Web site, and all posted and associated content indicates your acceptance of BioOne's Terms of Use, available at www.bioone.org/page/terms_of_use.Usage of BioOne content is strictly limited to personal, educational, and non-commercial use. Commercial inquiries or rights and permissions requests should be directed to the individual publisher as copyright holder. ABSTRACT The refuge plus high-dose strategy for resistance management assumes that the frequency of resistance alleles is low. We used an F 2 screen to estimate the frequency of resistance to transgenic corn that produces Bacillus thuringiensis Berliner Cry1Ab toxin (Bt corn) in an Iowa population of European corn borer, Ostrinia nubilalis (Hü bner). We also proposed a modiÞcation to the statistical analysis of the F 2 screen that extends its application for nonuniform prior distributions and for repeated sampling of a single population. Based on a sample of 188 isofemale lines derived from females caught at light traps during the 2nd ßight of 1997, we show with 95% conÞdence that the frequency of resistance to Bt corn was Ͻ3.9 ϫ 10 Ϫ3 in this Iowa population. These results provide w...

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Patterns of body size and net construction suggest that current speed and food-particle concentration (not size) influence the distribution of suspension-feeding caddisflies on a downstream gradient. Large ancestral taxa with high filtration rates occur in resource-poor upstream habitats; more derived members of the phylogeny enter successively in downstream reaches with slower current and greater concentrations of particulate food.