The use of transgenic (Bt) cotton (Ingard® and more recently Bollgard II®) has greatly reduced the use of insecticides in Australian cotton production and the status of key lepidopteran pests such as Helicoverpa spp. But the potential for these moths to develop resistance to Bt remains a major challenge for the industry. A resistance management plan has been adopted, part of which is the mandatory requirement for Bt cotton growers to provide refuge crops (no Bt exposure) as sources of susceptible moths. Such moths are expected to mate with potentially resistant moths arising from the Bt crops and help reduce the chance of resistance developing more broadly. During the Ingard® era, the relative moth productions of various refuge crop options were identified. However, only limited research has been devoted to identifying the degree of cross-mating of moths between refuges and Bt cotton crops.

This project’s research determined the incidence of cross-mating of Helicoverpa in key refuge crop ‐ Bollgard II® cotton combinations. It concluded that mating of H. armigera moths from different plant host origins occurs at random – as assumed under the Resistance Management Strategy adopted by the Australian Cotton Industry. However, our knowledge for H. punctigera in this regard remains very limited – and H. punctigera has emerged through recent surveys of Bt resistance alleles to be surprisingly important too. In addition, we began to identify the degree of coverage achieved spatially (landscape-scale) by refuge-derived, susceptible moths, by surveying intensively all refuge crops within a single cotton production region (St George) throughout a growing season. This work will be continued in a new project (2009‐12). Further, we identified means by which the performance of refuges (production of Helicoverpa) can be enhanced, in particular through the use of moth attractants such as those in , and through novel refuge crop options (e.g. pigeon pea and mixed crops for dryland systems, split-planting of unsprayed conventional cotton for irrigated systems). The ultimate aim of the research is to optimise the efficiency of refuges, and enable maximum, effective production for least input by farmers.

We also maintained our ongoing monitoring programs for Helicoverpa moths (pheromone trap grids in the L. Namoi and St George regions) to provide local guidance to growers of population trends, as well as identifying long-term patterns in the abundance of these key pests at seasonal and regional scales. The abundance of Helicoverpa spp was in general low during the tenure of this project. Rearing of field-collected eggs, larvae and pupae of Helicoverpa also suggested that the incidence of natural enemies (e.g. pupal parasitoids) is currently quite high. This raises concerns for the effective production of susceptible moths from refuges. Whilst the abundance of Helicoverpa within refuges was relatively low during 2006-09, it was not outside the range documented in previous years. The performances of refuges will be closely monitored in the new project.

During the project, we re-analysed old data sets to determine e.g. the degree of evidence that exists that supports the notion that rainfall patterns in inland areas of Australia drive the production and migration of H. punctigera from there to the eastern cropping regions, such as the L. Namoi. We found little evidence of correlations between inland rainfall patterns and the numbers of H. Punctigera subsequently trapped near Narrabri since the early 1990’s. Rather, we found some evidence of early season abundance of H. punctigera being related to numbers at the end of the previous cropping season – suggesting greater local over-wintering than previously thought to occur. Clearly, we still have much to learn concerning the ecology of these key pests.