The cotton industry relies on GM cotton expressing insecticidal toxins from Bacillus thuringiensis (Bt). This provides resistance to key pests of cotton, the bollworm Helicoverpa armigera and the native budworm H. punctigera. Growers benefit by reduced losses to the pests, and the amount of insecticide used on cotton is down by 80%, with major environmental benefits. However, as with all toxins, there is potential for the pests to develop resistance. The industry has comprehensive Resistance Management Plans (RMPs) to counter this, based on scientific understanding of the genetics and ecology of the pests. RMPs are uniformly adopted as legal requirements for growing Bt cotton, and have prevented the failure of Bt cotton for over a decade. They are focused on H. armigera, because from the 1960s through the 1990s, this species repeatedly developed resistance to conventional insecticides, and its ecology was thought to favour the buildup of resistant alleles. In contrast, H. punctigera was thought to pose little risk, because it did not overwinter in cotton regions and immigration of susceptible moths from inland populations was common.

However, recent monitoring of the frequency of alleles conferring resistance to one of the two Bt toxins (Cry2Ab) has cast doubt on these assumptions. In the 2008-09 season Cry2Ab resistance in H. punctigera rose considerably above background levels, and higher than in H. armigera. This indicates that RMPs must place more emphasis on H. punctigera. It also suggests that either our previous understanding of the ecology of this species (based on work done mainly in the 1980's) was inadequate, or something (eg climate) has changed. This project aims to provide improved understanding of the ecology of H. punctigera, especially overwintering of pupae in cotton regions and immigration from non-cropping regions where there is no selection pressure from Bt cotton, notably inland Australia. It includes laboratory studies on the induction and termination of diapause in relation to temperature, daylength and insect nutrition, and field cage studies in cotton regions and in inland regions, to determine the level of overwintering survival and the timing of moth emergence.

Field surveys of inland regions during the winter breeding period will determine host plant responses to rainfall and abundance of Helicoverpa larvae, and spring trapping studies and surveys in spring crops will estimate levels of migration. Results will be compared with earlier studies in the 1980's and 1990's to investigate the possibility of long-term changes to the ecology of H. punctigera. Findings will be reflected in changes to RMPs for Bt cotton.