The effects of rotation crops and their management on soil properties, and irrigated cotton productivity and profitability were evaluated from 1993 to 1996 in some typical cracking clays (V ertisols) of the Namoi and Macquarie valleys of New South Wales. The project consisted of 3 field experiments: (a) an experiment on tillage systems and rotations (intensive tillage or minimum tillage sown with continuous cotton, and minimum tillage sown with a cotton-wheat sequence which were imposed in 1985, on which three rotations: cowpea-cotton, continuous cotton and fallow-cotton were superimposed in 1993) located at the Australian Cotton Research Institute near Narrabri; (b) a rotation crop management experiment (wheat+l40 kg ha-1 N-cotton, unfertilized wheat-cotton, and winter grain legume-cotton sequences where the legume grain was either harvested or incorporated) located near Wee Waa; and ( c) a rotation crop management experiment [high input (99 kg N and 17 kg P ha-1, irrigated) wheat-cotton, low input (16 kg N and 17 kg P ha-1, rainfed) wheat-cotton, rainfed field pea-cotton, summer fallow-cotton, low input wheat-dolichos-cotton, low input wheat-dolichos +24 kg P & 73 kg K ha-1-cotton, and continuous cotton sequences] located near Warren. (The low input wheat-dolichos/P+K fertilizer-cotton sequence was replaced by a faba bean-cotton sequence in 1995). Soil properties which were monitored to a depth of 0.6 min every site included organic matter fractions, plastic limit, strength, shrinkage indices derived from shrinkage curves, exchangeable Ca, Mg, Kand Na, pH, nitrate-N and electrical conductivity. Profile water content and water extraction to 1.2 m, nutrient uptake, crop vegetative growth, cotton lint yield and fibre quality were also quantified. Economic rerorns were evaluated by comparing gross margins for rotation crop-cotton sequences.

Objectives: A). To establish the uptake and partitioning patterns of potassium in cotton. B). To establish the most suitable predictor of deficiency amongst soil, leaf blade, leaf petiole and leaf petiole sap potassium; including the most appropriate potassium test. C). To establish appropriate methods of within season amelioration of potassium deficiency.

Aims: * Determine the economic impact of thrips on cotton and evaluate new means of control. * Evaluate the range and possible mechanisms of plant resistance to thrips and mites. * Investigate host preferences of thrips and manipulation of hosts to increase thrips predation. * Investigate further the impact of thrips on mites through predation, induced resistance and effects on plant quality. * Refine action thresholds for the control of two-spotted spider mites on cotton. * Evaluate the efficacy of new acaricides and investigate novel technologies for controlling mites. * Determine resistance levels in mites to acaricides and factors influencing development of resistance. * Evaluate the effect of early season insecticides on mites and their predators.

The goals of this research were: 1. measure the soil stresses and deformations due to "edge of bed" operations, and measure the changes to soil physical properties (infiltration, aeration, strength) that result. This was to be pursued in collaboration with the anticipated rotation experiments led by Cooper and the structure project led by Koppi; 2. correlate the field performance of operations with soil conditions, in order to detennine optimum conditions for operations; 3. transfer the conclusions via SOILPAK, the Australian Cotton Grower and Grower Conferences

This project had two major aims consistent with the overall goal of controlling Verticillium wilt in cultivated cotton (Gossypium hirsutum). The first aim was to employ molecular genetic techniques to differentiate between isolates of the fungal pathogen Verticillium dahliae in order to develop a better understanding of the epidemiology of Verticillium wilt disease in cotton. The second aim was to produce molecular genetic fingerprints of the wilt-tolerant cotton cultivars currently being developed by the CSIRO to assist in the identification and tracking of potential genes for disease resistance in the plant breeding program.

aims of this study were to: obtain base-line data against 12 pesticides and to conduct an initial evaluation of the current resistance status of field-collected cotton aphid strains. To that end laboratory studies were required to establish base-line data for Australian cotton aphid. Susceptible strains of cotton aphid were established and breed in purpose built cages. When sufficient numbers of aphids were available they were assayed against a range of established and potential pesticides to establish base line-data. Once generated, the base-line data was used to screen a number of field-collected strains for resistance.

To develop resistance management strategies for organophosphates (OP's) carbamates, insect growth regulators (IGR's) and new insecticide groups, such as the pyrroles based on a sound understanding of resistance mechanisms 2. To evaluate the importance of a newly discovered pyrethroid resistance mechanism and develop low cost, rapid biochemical techniques for the detection of pyrethroid, carbamate and organophosphate resistance.

Pyrethroid resistance levels in Helicoverpa armigera have continued to escalate slowly to around 80-90% but endosulfan resistance has stabilised at about half that level. Resistance to the partial resistance breaking pyrethroid bifenthrin has increased slightly but on average, resistance levels to this product are about half those to the other conventional synthetic pyrethroids. Profenofos resistance is still low in all areas except for an incipient problem in central Queensland. Via tolerance curve analyses indicate the emergence of elevated levels of pyrethroid resistance mechanisms. These ire synergisable by alternative mfo (mixed function oxidase) inhibitors to Pbo (piperonyl butoxide) and are overcome by synergophore pyrethroid analogues such as Series Two and prallethrin but not by esterase inhibitors nor by a non-ester pyrethroid analogue (silafluofen). This indicates the possible development of new isomorphs of P450 monooxygenases (mfos) synergised by alternate chemical classes of mfo inhibitors such as the propynyl ethers but not fully synergisable by Pbo. Laboratory studies indicated some potential synergists for field evaluation (ethion, malathion, phosmet) but most compounds tested were ineffective, including profenofos, trichlorfon, phoxim, azamethiphos and other esterase and glutathione inhibitors. Cyclodiene resistance did not give cross resistance to the avennectins. Baseline susceptible data and discriminating doses were evaluated for three classes of new insecticides; spinosad, the pyrrole chlorfenapyr and the avermectins (abamectin and emamectin benzoate). Abamectin was identified as a potential new replacement for endosulfan for early season Helicoverpa punctigera control. Helicoverpa punctigera resistance levels to both endosulfan and pyrethroids have remained low. )

A Heliothis NPV formulation, GemStar, showed promise as a basis for successful selective, non-chemical insect control on cotton. Trials were conducted with the virus as a stand-alone insecticide on dryland cotton at Dalby, Q. by D. Murray (QDPI), and in conjunction with Envirofeast on irrigated cotton at Moree by R. Mensah, (NSW Agriculture). On dryland cotton at Dalby, Qld, yields were equivalent to those with conventional chemical control at one of the two sites. The virus failed to contain a heavy infestation of Heliothis in February 1996, but neither did conventional insecticides. In an IPM programme on cotton with lucerne strip cropping at Moree involving 4 Envirofeast sprays followed by 3 sprays of the virus combined with Envirofeast and a clean-up chemical spray, yields were similar to those obtained with a conventional insecticidal regimen. Predator numbers were higher in the Envirofeast/GemStar plots than in other "soft11 treatments", Envirofeast/endosulfan or Envirofeast/Bt endosulfan, suggesting that any disruption to predators by GemStar was at a low level. Bioassays indicated that GemStar maintained its potency during on-farm, refrigerated storage. Levels of infection achieved on cotton were variable but the overall average was about 55%. This suggests that the use of the virus should be integrated with other Heliothis control measures. Thresholds frequently exceeded 2 larvae per row metre without undue damage to the crops, suggesting that this biocontrol system provided greater flexibility in control response than with chemical insecticides. This aspect requires further investigation to determine appropriate thresholds.

The project was teminated by CRDC after two years and therefore could not meet its final objectives. Good technical progress was made and the resources and information that were obtained remain available for the future. One particular benefit of the project was seen by the CRDC review. held in January 1995. as being that the knowledgeledge gained would assist in resistance management for Bt. In an unexected way it did this by highlighting the need for us to create a genetic ma Heliothis armigea. In the case of CSE36C. The re-existence of a genetic ma of the related American species. Heliothis virescens. Allowed us rapidly and cost-effectively to decide whether endosulfan resistance was due to a mutation in the GAB~ gene. Our abilty to use information from the American species relied on the ha1) y and unusual coincidence that endosulfan resistance is sex-linked (i.e. its chromosomal location ii/. Armigera is known). This is a rare. If not unique. Situation and almost certainly we will not have this advantage when we are faced with H. armigera resistant to Bt cotton. Creating a genetic map iii/.armigera before Bt resistance appears in the field would eliminate reliance on luck and greatly facilitate characterisation and detection of resistance genes when they a ear. It would do this by providing markers which could be used to determine the chromosomal location of any resistance genes. Even at the crudest level this would be a ve1y valuable tool. It is therefore one of the most cost-effective steps that the cotton industiy can take as insurance against Bt resistance.