Abundance of Helicoverpa (Lepidoptera: Noctuidae) pupae under cotton and other crops in central Queensland: implications for resistance management

Abstract

Planting of refuge crops and post-harvest cultivation of soil in winter are key elements of resistance management strategies (RMS) for Bt-transgenic (Ingard®) and conventional cottons in southern Queensland and New South Wales. As part of a larger project to examine the feasibility of growing Ingard® in central Queensland (CQ), field assessments were conducted during the 1996–97 growing season to examine the adequacy of the southern Bt-cotton RMS under local environmental conditions. The suitability of cotton and a number of other field crops as refuges for Bt-cotton was assessed in terms or their relative Helicoverpa pupal productivity. The practicality and potential effectiveness of post-harvest cultivation under CQ conditions were also assessed. Field assessments show that pigeon pea has the greatest potential as a refuge for Bt-cotton. Unsprayed cotton, sorghum and maize also produced substantially high pupal densities and hence are suitable refuge options, but they will require larger areas to be planted relative to pigeon pea. Post-harvest cultivation in cotton fields is largely ineffective for resistance management under CQ conditions. A Bt-cotton RMS for CQ is proposed. The CQ strategy includes refuge crop options contained in the southern strategy and the use of late season trap-crops of pigeon pea as an alternative to post-harvest cultivation.