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Helicoverpa zea Fitness on Bt Corn and Cotton in Eastern North Carolina: Potential Effects of Alternate Host Crops and Pyramided Bt Plants

Ryan W. Kurtz, Fred Gould, J.R. Bradley, Jr., and John W. Van Duyn


A deterministic population genetics model was developed to evaluate how corn and cotton with pyramided Bt toxins, Non-Bt cotton refuges, and alternate H. zea crop host refuges could affect Bt resistance development in a H. zea population in eastern North Carolina. Empirical estimates of resistance allele frequencies for H. zea in the literature,adult production on Bt and Non-Bt corn and cotton, and proportions of larvae developing on cotton, corn, soybeans, and peanuts during each of three generations were used as model parameters. The frequency of resistant individuals is calculated at the end of each year, and resistance is considered problematic in the year when 25% of the individuals are homozygous for all alleles conferring resistance to a specific Bt crop. Model runs predict that the planting of pyramided Bt cultivars, the Non-Bt corn refuge, and alternate host refuges will each have a greater impact on resistance development than a 5%, structured, Non-Bt cotton refuge.

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Document last modified 04/27/04