High adoption rates of genetically modified, insecticidal Bt cotton lead to regional changes inpest management practice with potential consequences for populations of the mainlepidopteran pest, Helicoverpa spp., and natural enemies in Bt cotton and neighbouring crops.To test the hypothesis that Bt cotton functions as a sink and other crops as potential sourcesfor Helicoverpa spp., we determined Helicoverpa spp. egg densities in 24 Bt cotton fields inthree landscapes in the Darling Downs, QLD, Australia. Egg densities peaked in January2010, when cotton started flowering, and decreased afterwards, except in one landscape,where a second peak was observed at the end of February. In this landscape, rainfall allowedplanting of large areas of sorghum early in the season. Consequently, the late season peak islikely to be a result of third generation moths recruited from sorghum. In the two otherlandscapes, non-cotton crops were planted later in the season or not at all. While H.punctigera dominated the samples early in the season, H. armigera was most frequent inJanuary, but H. punctigera populations increased again towards the end of the season. To testthe hypothesis that natural enemies of Helicoverpa spp. eggs remain unaffected by Bt cotton,we followed parasitization rates of field collected and sentinel Helicoverpa spp. eggs andpredation rates of sentinel eggs. Egg parasitoids were not found before January, but 40-80%of the field collected eggs were parasitized thereafter. Parasitoids were clearly dominated byTrichogrammatidae. From our samples, there was no indication that Bt cotton affected eggparasitoids or predators. The project is continuing in the field season 2010/11 with Australianfunding from Cotton CRC and GRDC. Data will be collected in a similar way and moredetailed analyses will be conducted with the complete data set.