When comparing BollgardII with conventional cotton, the lower water requirement and higher lint yield of Bollgard II was explained by greater insect damage in conventional cotton. The effect of this damage was to delay time to maturity and increase leaf area of the conventional variety, which in turn increased crop water use. In situations where pest damage is minimal, variety differences are unlikely or could favour the conventional variety where tipping is the only damage. Water stress equivalent to extraction of > 60% of plant available water at mid flowering and cut-out reduced Bollgard II yields by 24 and 36%, compared with 2 and 17% in conventional. A much higher boll load at the time of stress prevented compensation in the BollgardII variety. Over 2 seasons the response of BollgardII to different irrigation frequencies (deficits) was strongly influenced by evaporative demand. Where the deficit was about 80mm (40% of PAWC) yield was increased by 20% in the lower evaporative demand season. The yield difference was minimal with a deficit < 40mm (20% of PAWC). Generally Bollgard II produced consistently higher yields at smaller deficits (35 to 54mm). However yield at a 35 mm deficit was reduced in 2007 / 08 by rainfall coinciding with irrigation.

OBJECTIVES Reason for Travel Dr Denholm is an international authority on the management of resistant Bemisia tabaci on cotton. 1. Funds were requested to bring Dr Denholm to Australia to present a keynote address on whitefly management at a special cotton entomology symposium at the Australian Entomological Society's Scientific Conference, Tamworth 23 -28 th September 1995. 2. Dr Denholm was also requested to address a CRDC/HRDC Workshop on Biotype B Bemisia tabaci in Australia, discussing the options for the management of resistant B. tabaci on cotton in Australia, held at the Airport Hilton, Sydney 10October1995. 3. To discuss progress in collaborative research on B-type B. tabaci and Helicoverpa resistance biochemistry between Dr Gunning and the Rothamsted Insecticide Resistance Group

The position of Cotton Industry Development Officer (C.l.D.O) in the Macquarie Valley was implemented in 1993-94 because much good research generated at Narrabri was not being adopted by local growers. The reason was that there existed a perception that this research was not relevant to the conditions in the Macquarie. There was also concern that trials carried out in small plots did not accurately represent farm scale production.

OBJECTIVES 1. To undertake a comprehensive sutvey of the Australian distribution of B. biotype B. tabaci . 2. To sutvey cotton for the presence of B, biotype B. tabaci 3. 4. To develop and asses the usefulness of a field "squash test" to identify B -biotype B. tabaci. To undertake preliminary bioassay studies to identify insecticide resistance status of this insect.

Cotton plants expressing the CrylAc toxin from Bt are near to commercial release. These plants have been developed to aid in the control of heliothis caterpillars, the primary target of insecticide usage in cotton production. Despite initial hopes, the plants will not give season-long control of heliothis. Late in the season, heliothis grubs can survive and grow on transgenic cotton plants. Thus, in these mature plants either the amount of Bt toxin is lower than it was earlier in the season, or the Bt toxin is partially inactivated by the leaf. The decline in the efficacy of plants late season makes resistance management more difficult than if expression of the toxin was maintained at a high level. This project examined the potential of transgenic Bt plants to select for resistance to the insect pest Helicoverpa armigera. We have focused on gaining an understanding of why the plants are able to control heliothis caterpillars late in the season. It is at this time that selection for resistance may well be at a maximum. At the beginning of our study nothing was known about the cause of the decline in toxin levels, nor were techniques available that would enable us to quantify those levels. Thus, we have had to focus on developing the necessary techniques to study the performance of transgenic plants grown under field conditions. We have successfully developed a leaf bioassay test that can measure relative changes in toxicity of Bt leaves. We observed a 3-fold decline in toxicity of the plants from young plants, before budding, to mature plants with bolls. This decline is only small so it suggests that the level of Bt toxin in young cotton plants may not be much above the level to kill heliothis. A number of additional factors were observed to affect the efficacy of the Bt. The potency of Dipel 2X was reduced to half when it was fed to larvae in a soy bean based diet, compared with one of chickpea. Some component of older leaves also appears to reduce the availability of Bt toxin to larvae feeding on a mixture. Preliminary experiments also indicate that stressing plants may also affect Bt levels, although further experiments are being carried out to elucidate the precise factors. In a second phase of the project we have attempted to develop a strain of H. armigera resistant to Bt We have modified and developed a technique that produces mutant H. armigera. These mutants have been screened for individuals carrying Bt resistant genes. One candidate resistant strain has been established. Although its level of resistance to Dipel is low, it appears to survive better on transgenic plants compared with controls. We are investigating this strain further.

In March 1995 the Cotton Research and Development Corporation (CRDC) asked the Centre for International Economics to prepare a report on the cotton industry and its economic impact. This report was to provide a basis for assessment of the key policy, economic, market and environmental issues facing the industry.

Commissioned in November 1994, it was funded equally by the Cotton Research and Development Corporation (CRDC) and Sainty and Associates with a budget of $47 000 and the following work was undertaken: 1. Azolla evaporation study (University of Western Sydney). 2. Floating ring evaporation study (RMIT, Melbourne). 3. Evaporation mitigation from on-farm water storages (CSIRO Centre for Environmental Mechanics). 4. Study tour of six cotton farms (CSIRO Division of Water Resources, Sainty and Associates).

This study was initiated to quantify the impact of those predators commonly found in Australian cotton fields and thereby reveal the importance of the various predatory species in Helicoverpa pest management. Trials to investigate the commercial feasibility of growing cotton under 'soft-option' strategies (that is, without pyrethroids or endosulfan) at 'Midkin' (Auscott Pty. Ltd., Moree) provided populations of Helicoverpa and predators for our comparisons. Field work was also conducted on organically-grown cotton at 'Alcheringa', near Boggabilla, and Wilby', near North Star. Unsprayed cotton from these sites and from research sites of the Australian Cotton Research Institute was also used, and these field studies were complemented with laboratory studies of predation carried out at the University of New England.

In Australia, management of cotton pests is insecticide based. Beneficial insects are neglected due to the disruptive impact of the insecticides, lack of techniques to maximise their abundance and effectiveness and also lack of ecological diversity in Australian cotton systems which are monoculture and militate against beneficial arthropods. Studies to develop a control strategy for early season pests on cotton which has minimal effect on natural enemies commenced in July 1992 until June 1995. These studies showed that provision of supplementary food through Envirofeast spray can attract, conserve and augment naturally-ocurring predatory insects, including transverse, three-banded, twospotted ladybird beetles, red and blue beetle, big-eyed bug, damsel bug and green lacewings. These insects are natural enemies of cotton pests especially Helicoverpa spp. However, thiodicarb and endosulfan which were previously known to the industry to be "soft" on beneficial insects were shown in this study to significantly reduce predatory insect numbers. Interplanting of luceme, as strips within cotton farms, served as a trap crop or sink for early season cotton pests such as green mirids and as refugia for predatory insects. Green mirids and predatory insects on cotton can be effectively sampled using Dvac. The integration of Envirofeast and the lucerne/cotton interplant (i.e. refugia technology) into a pest management system eliminated the need for early season synthetic insecticide sprays and reduced total synthetic insecticide sprays per season by 60 per cent. Envirofeast product unfortunately is not rainfast and production technology needs to be developed to produce the product in large quantities for commercial use. With resistance of Helicoverpa spp. to insecticides increasing, and the possibility that insect resistance will be a major problem even with transgenic cotton, the control strategy developed in this study should be integrated with transgenic cotton to sustain future cotton production.

Various parasitoids are active on cotton crops from early seedling growth right through to defoliation. The parasitoids of greatest interest on the cotton crop are those that attack the key pest, heliothis, and which may add to the mortality of egg, larval and pupal stages that is provided by other biotic and abiotic factors. During recent years most research on parasitoids has concentrated on native agents attacking the egg and early larval stages.