The Australian cotton industry is now heavily reliant on genetically engineered Bt cotton for the control of Helicoverpa spp. and other moth pests. The introduction of this technology has been associated with a reduction in insecticide use of around 80%. The lifestyle improvements and the reduced environmental impacts of pesticides have considerably benefited growers and the community. The industry's social license to operate depends on maintaining these environmental and community credits. In turn, this depends on maintaining the effectiveness of Bt, in particular by avoiding resistance in Helicoverpa spp.The industry has a rigorous and widely adopted resistance management strategy, in which the planting of refuges (crops that breed unselected insects) is a key component. It is important that refuge efficiency is maximized. We need refuges which produce the highest numbers of susceptible moths relative to potentially resistant ones emerging from Bt cotton, and produce them when and where they are required. This project focused on the possibility of improving the effectiveness of refuges, or reducing the number of moths emerging from Bt cotton, by chemical modification of insect behaviour. The development by researchers in this project of the novel moth attractant Magnet® means that we now have the capacity to move Helicoverpa populations around on a diverse landscape of Bt cotton and refuge crops, over large distances. This project aimed to translate that capacity into more effective refuge management, to enable reductions in areas required for refuges, or more robust resistance management strategies, or both. It aimed to explore new approaches with an existing product (Magnet®), and develop new products specifically to enhance refuges.In this project we have demonstrated that carefully timed and placed applications of Magnet® in summer can reduce oviposition on Bt cotton, leading to fewer surviving larvae and this a reduced population of potentially resistant moths. We have also demonstrated that concerns expressed by some researchers that in some circumstances Magnet® might disproportionately attract moths from refuges, or increase oviposition leading to potentially increased selection pressure, are unlikely to be realised. We have shown that application of Magnet® to spring wheat can attract and kill H. armigera moths, which may allow the use of the product in remediation of cotton fields which have not been adequately cultivated to destroy overwintering pupae, as required by resistance management plans. We have also developed the concept of moth busting in late season cotton to directly target potentially resistant moths, and this has been further explored through a one-year preliminary project (reported separately) which studied the technique at the farm scale.Clarification of the potential for using Magnet® or similar products for resistance management will depend on the development of a method of identifying the host origin of moths killed by the product, or collected from the general population using various trapping methods. We have therefore initiated studies to investigate the potential of biochemical markers, especially cuticular alkanes, to provide this information. This work requires specialised expertise in organic chemistry, and has therefore been continued in another project. Results from the project are made available to the Transgenic & Insecticide Management Strategies Committee (TIMS) of Cotton Australia, and the industry&#39s scientific forum for resistance management, REFCOM. The project will contribute to improved resistance management for transgenic Bt cotton, but further field testing on area-wide scales over the next three years will be necessary to generate the robust data to support such changes.