Monday, December 10, 2007 - 8:05 AM

Does refuge width or distance from Bt fields decrease contamination by transgenes?

Shannon M. Heuberger,, University of Arizona, Dept. of Entomology, P.O. Box 2100 (36), Tucson, AZ, Bruce E. Tabashnik,, University of Arizona, Entomology, Forbes 410, PO Box 2100: (36), Tucson, AZ, Yves Carriere,, University of Arizona, Department of Entomology, 410 Forbes Building, P.O. Box 210036, Tucson, AZ, and Timothy Dennehy,, University of Arizona, 410 Forbes Bldg, University of Arizona Dept of Entomology, Tucson, AZ.

Outcrossing of non-Bt cotton (Gossypium hirsutum (L.)) in refuges by transgenic Bt cultivars could potentially reduce the efficacy of refuges for delaying resistance in seed feeding pests. Based on reports that outcrossing of non-Bt cotton decreased as distance into non-Bt cotton fields increased in small-scale studies, we hypothesized that increasing refuge width or distance from Bt fields would reduce outcrossing. In a large-scale study in Arizona, we measured outcrossing in experimental plots and commercial fields, comparing outcrossing between in-field (narrow) and external (wide) refuges and among rows of refuges at various distances from Bt fields. Some refuges, including those in tightly controlled experimental plots, contained adventitious Bt plants; a phenomenon that appears common in Arizona. There was no significant decrease in outcrossing as refuge width or distance from Bt fields increased. We hypothesize that Bt plants in the refuges were more significant pollen donors than nearby Bt fields, overshadowing the expected association between distance from Bt fields and outcrossing.

Species 1: Lepidoptera Gelechiidae Pectinophora gossypiella (pink bollworm)
Species 2: Hymenoptera Apidae Apis mellifera (honey bee)