Technical Abstract: Transgenic cotton (Bt) with the gene incorporated that mediates production of the Cry1Ac toxic crystalline protein has been highly effective in PBW management systems. Development of resistance to the Bt toxic protein has been considered a major threat to long-term effective performance in the field. In spite of the rapid selection of PBW strains with high levels of Bt resistance in the laboratory, under field conditions in Arizona, some PBW larvae have actually become more susceptible to the Cry1Ac toxic protein. The reason(s) for the difference between laboratory and field responses to Cry1Ac exposure are unexplained. Nonetheless, the Environmental Protection Agency mandates that Bt cotton growers also plant some non-Bt cotton (refugia) nearby. Proximity and amount of non-Bt cotton in relation to the Bt cotton are specifically described. The refugia concept is based on production of large numbers of Bt susceptible PBW moths in non-Bt cotton that will be available for mating with the few low-level resistant moths surviving in Bt cotton. PBW moth dispersal from non-Bt cotton, oviposition and mating interaction are some of the critical issues affecting the performance of the refugia. For PBW, refugia plants are located within Bt cotton fields and the existence of potential PBW moth mating and oviposition interactions with Bt and non-Bt plants in close proximity are unknown.