Information on the likely tinting of Autumn diapause induction in Helicoverpa is useful for growers planning to cultivate cotton stubble for &quote;pupae busting&quote;. Cultivation to control pupae is mandatory for INGARD cotton, and it is recommended for conventional cotton as part of the Australian Insecticide Resistance Management Strategy (Forrester and Bird 1996). The benefits of controlling H. armigera pupae in this way have been extensively published within the cotton industry (Slack-Smith et al 1997, Fitt et al 1993, Wilson 1993, Murray and Titmarsh 1990).

Transgenic plants are rapidly dominating World agriculture and already the produce from millions of acres of transgenic insect and herbicide tolerant cotton, corn, soybean and canola being traded around the World, predominantly originating from the U. S. . By the end of the decade there will be few broad acre crops whose management would not have been changed uralterably by this new technology. The experiences from these early transgenic crops are in general good, providing good value to the farmer, but sporadic reports of poor performance of the transgenic traits and of variable performance of transgenic plants between different regions, suggest that we do not yet know enough about how genes function plants to perfectly predict the behaviour of transgenes under field conditions.

This project was designed to support the deployment and continued use of transgenic (INGARD) cotton in the Australian cotton industry. To maximise the efficacy and useful lifespan of transgenic cotton we need to monitor the production of the toxin from Bacillus thuringiensis (Bt) in cotton plants throughout the growing season. Transgenic cotton contains a gene which encodes for the production of an insecticidal crystal protein (referred to as the &quote;toxin&quote;) which is highly toxic to Iepidopteran species including Helicoverpa, a major pest in the Australian cotton industry. These plants have been shown to successfully produce the toxin, but field studies indicated that the efficacy of plants was reduced later in the season (Fitt et al 1994). The cause of this reduced efficacy was not understood, although it is possible that production of the toxin is influenced by plant age or reproductive stage, and/or by a variety of environmental factors. Also, to ensure that resistance management strategies designed for use with transgenic cotton are successful, we need to assess the exposure of insects to the toxin.

The past growing season (1997/98) was the second commercial year of INGARD cotton varieties with some 60,000 ha planted across all growing regions. In the first two seasons of commercial use INGARD varieties have reduced pesticide use by 50-60% and achieved similar or better yields to conventional varieties. This represents a significant step forward in reducing pesticide use in the cotton industry. There have been several reports from CRDC and Monsanto regarding the performance of INGARD crops in relation to pesticide use and economic value to growers and I don't intend covering these issues here. Obviously the bottom line when it comes to INGARD performance is efficacy, an issue which is amenable to research. To provide most value and ease of management, transgenic cotton crops need to provide consistent and hopefully high capacity to kill the target pests quickly ie. high efficacy. Early in development of transgenic cottons the expectation was that expression of the Bt protein would be consistent throughout growth of the crop and consequently that control of the target pests would be provided almost season long. The Cry1Ac gene is driven by a promoter which gives constitutive expression in all tissues in the plant, although there are significant differences between plant structures in the level of Bt protein production. However, from the very first year of small scale field trials it soon became evident that efficacy of leaves and reproductive tissues declined during plant growth and that some larvae were able to survive beyond first instar. It was not until lNGARD crops were grown on a commercial scale that the magnitude of these changes, and the variability which can occur between crops in different fields, farms and regions became fully apparent.

Organophosphate insecticides are valuable insecticides used to control Helicoverpa armigera on cotton in Australia. Organophosphates most commonly used for Helicoverpa spp. control, are profenofos, methyl parathion and chiorpyrifos. However, there is an emerging organophosphate resistance threat in Australian H. armigera, which is compounded by cross resistance between profenofos and methyl parathion. An insensitive acetylcholinesterase has been identified as the common resistance mechanism. No resistance to chlorpyrifos has been detected and acetylcholinesterase remains fully sensitive to chlorpyrifos and its oxon

Australian cotton production relies heavily on the use of pesticides for control of Helicoverpa spp. As a result insecticide resistance has become a major problem (Daly and Paschalidis 1994). With current problems of resistance in Helicoverpa armigera (Hubner) to pesticides and the importance of aiding resistance management in Bt cotton, greater emphasis has been placed on research that investigates the role of beneficial insects as control agents of Helicoverpa. To date, this has largely been done by investigating total predator abundance relationships with prey abundance (Staley 1997). The role of individual predator species has not been widely investigated and our understanding of their roles in control of pests is limited. If predators are to be utilised in cotton growing systems it is imperative to understand the role of individual species. This will aid in the assessment of the ability of total predator populations to control Helicoverpa and other secondary pests. As many of the predator species found in cotton are generalist feeders this work includes an understanding of how each species performs given that relative abundance of prey types varies in cotton fields.

Good average irrigated yields have been achieved on the Darling Downs by most growers this season while dryland crops on average did not fare so well due to the unseasonal hot dry conditions. The region had to contend with high heliothis pressure i.e. more than 15 eggs per metre for much of the season, and this coupled with high levels of resistance (starting with 80% H. armigera in mid-November) has made control costs very high, with some yield forgone at the same time from insect damage. This combination of high pressure and high levels of resistance from early season onward makes for a very difficult outlook.

Helicoverpa spp are considered the most damaging insect pests of cotton in Australia and consequently have attracted considerable research attention. Problems with insecticide resistance and possible environmental damage associated with excessive insecticide use has led to concerted efforts to reduce spraying in cotton. Integrated Pest Management(IPM) methods and area wide management have emerged as new tactics and are underpinned by decision support systems, including CottonLOGIC. However, despite the myriad of factors to be taken into consideration before spraying, the most important remains the &quote;pest threshold&quote;, as measured by crop scouting. In the case on Inguard cotton, the established threshold for Helicoverpa is a total of 2 larvae/m row in all crop growth phases(Anon. 2002). Early experiments with INGARD at Kununurra raised concerns that the fixed threshold of 2 larvae/m may not be appropriate for the unusual winter growing environment in the Kimberley. The concerns were twofold, firstly because the &quote;reverse&quote; growing season meant that cotton growth was rapid in high temperatures at the beginning and end of the season but slow during boll development in mid-season, and secondly, that extensive periods of &quote;sub-threshold damage were often observed. To test the validity of established Helicoverpa thresholds in the winter system, a series of field trials were conducted between 1998 and 2001 with the aim of developing a more dynamic and responsive threshold to better reflect the growth stage of the crop and the impact of insect damage

We compared the responses of dryland and irrigated cotton to damage caused by two spotted spider mites in a field experiment at Narrabri. Mites colonies developed at similar rates in irrigated and dryland crops. Despite the similar intensity of infestation, visual symptoms of mite injury were more marked on irrigated plants than on their dryland counterparts. Lint yield of unstressed controls (irrigated, no mites) was 7.8 bales per ha. Water deficit alone reduced yield by 30%. Mites reduced yield more in irrigated (92%) than in dryland crops (72%). Under our experimental conditions, mechanisms of adjustment to water deficit may have enhanced cotton resistance to mites

Dry season cotton production in northern Australia faces considerable challenges if it is to emerge as a sustainable industry. Water for irrigation is abundant in the Ord River Irrigation Area (ORIA) and there are prospects of an increase in arable land with the future development of Ord Stage II. Yields from research trials have been encouraging and some of the early problems, such as shorter fibre length, have been overcome by growing adapted cultivars that produce longer fibres (i.e. SiCot 289I and Siokra V161). Results from initial dry season trials have been reported previously (Strickland and Constable 1995; Yeates at al 1996; Yeates and Constable 1998; Strickland et a1 1998) and management of issues such as irrigation scheduling, fertiliser requirements and the time of sowing are currently brining addressed. However several areas remain that require further research.