The Field to Fibre course, which is a formal three 3 day course, is presented in Geelong at

CSME. It gives participants an opportunity to interact with leading researchers

on allaspects of the cotton production pipeline including global perspective,

fibre properties, agronomy, picking, ginning, classing, marketing, yarn

formation, fabricformation and dyeing and finishing. A strong emphasisis

placed on the impacts offibre quality on textile processing. Information is

presented by way of lectures and practical demonstrations using the modem

commercial cotton spinning and processing equipment available at CTF

The course is constantly updated with all practical suggestions considered, to

ensure that the course stays relevant and current.

Compaction caused by machinery traffic can have severe yield consequences. Compaction increases soil strength and reduces soil porosity, which hinders root growth, moisture and nutrient uptake, and plant growth. GPS-auto steer and modification of machines to 3 m wheel centres can minimise compaction of fields. Conventional 1 m cotton does not accommodate for 3 m wheel centres so row spacing can be altered to alleviate this issue. The aim of the experiment in this study was to test the hypothesis: is cotton yield and fibre quality in wide 1.5 m row the same as conventional 1 m rows? There were two main components to the experiment at Auscott Warren farm, a replicated plot experiment and a paddock scale whole block experiment. The replicated experiment was a RCB design with nine replicates of 1 m and 1.5 m row treatments. The paddock scale whole block was two large field blocks of 1 m and 1.5 m row treatments. 1.5 m cotton was 10 cm taller than 1 m cotton. There was little difference in harvest index (60%) between the two configurations. The 1 m cotton yielded 1.8 bales/ha and 3.6 bales/ha higher than the 1.5 m cotton in the machine picked and handpicked replicated experiment, respectively. Yield of 1 m cotton mainly came from fruiting nodes 1-8, position 1. In contrast, yield in 1.5 m cotton mainly came from vegetative fruiting branches. There was a strong positive correlation (R2 = 0.99) between the number of bolls/m2 and yield, but only a weak correlation between lint per boll and yield (R2 = 0.28), and between number of bolls and lint per boll (R2 = 0.21). Only minor differences in fibre quality were observed. Gross margins of the two row configurations were very similar. Future research should quantify water usage to improve grower decision making.

In the 1996/97 season the Australian cotton industry adopted an insect-resistant variety of cotton (Ingard®) that is specific to the group of insects including the target Helicoverpa spp. but excluding predators and parasitoids of this pest. To prolong the efficacy of transgenic cotton against Helicoverpa spp., a resistance management plan (RMP) that restricted the area grown to Ingard® was implemented due to the critical importance of preserving the efficacy of the Cry1Ac gene.

In the 2004/5 season Bollgard II® replaced Ingard® as the transgenic variety of cotton available to Australian growers. It improves on Ingard® by incorporating an additional insecticide protein (Cry2Ab) to combat Helicoverpa. Due to the perceived difficulty for Helicoverpa spp. to evolve resistance to both proteins simultaneously within Bollgard II®, the RMP for transgenic cotton was relaxed to allow growers to plant up to 95% of the total area to this product. Bollgard II® was well adopted, with up to 70% (200,000 hectares) planted area throughout the industry.

The sensitivity of field-collected populations of Helicoverpa spp. to Bt products was assayed before and subsequent to the widespread deployment of Ingard® cotton expressing Cry1Ac in the mid-1990’s. From 1994/95 until 2002/03, a Bt spray (MVPII®) that contained formulation ingredients additional to Cry1Ac was used in the screens. The program also incorporated a Bt spray (DiPel®) with insecticidal proteins additional to Cry1Ac to test for resistance to combinations of Cry toxins. The program used only F0 screens however this method cannot detect individuals that are heterozygous for a recessive form of resistance.

During this project we developed screens using a pure Cry1Ac spore/crystal mix as our source of toxin. In anticipation of Bollgard II® replacing Ingard® in 2004/05, we developed methods to screen for resistance to Cry2Ab. In addition to performing F0 screens to detect major changes in gene frequencies, we incorporated an F2 screen to detect and ‘capture’ any rare resistance alleles in natural populations. This method allowed us to simultaneously screen for resistance to Cry1Ac and Cry2Ab, hence making the screens using DiPel® redundant.

There have been no reported field failures of Bollgard II® due to resistance. Our work shows that alleles that confer high level resistance by field populations of H. armigera and H. punctigera are rare for Cry1Ac. However, resistance genes for Cry2Ab in field populations of moths are surprisingly common. Our current best estimate is that they occur for H. armigera at a frequency of 0.004 (upper limit, 0.011; lower limit, 0.0008) and for H. punctigera at a frequency of 0.009 (upper limit, 0.005; lower limit, 0.0001). Individuals that carry a resistance allele for Cry2Ab are killed by Cry1Ac.

Our current knowledge of the ecology and resistance profiles of Australian Helicoverpa populations suggests the RMP is adequate to retard increases in the frequency of resistance. Computer models that incorporate our present knowledge of resistance frequencies, fitness costs, form of dominance and refuge size, suggest that Bollgard II® should prove effective at managing Helicoverpa in the medium to long term. However, it should be emphasised that these models assume that refuges are well maintained in order to produce large numbers of susceptible moths.

The purpose of the travel was to present at the 2005 Genetics Society of Australasia (GSA) conference in Auckland, on the results obtained from CRDC project UA12C to an international audience, and to gain information from other research undertaken in the field.

The need for a comprehensive and integrated weed identification and management guide for the Australian cotton industry has long been recognised. During May 2001, a meeting was held involving the Australian Cotton CRC weeds focus team, a team including both weeds researchers at ACRI and extension personnel from the National Cotton Extension Network, and representatives from the CRDC and ACGRA to discuss the production of WEEDpak.During the period May 2001 – June 2002 members of the weeds focus team, headed by the co-ordinating editor Dr Stephen Johnson, have worked to produce WEEDpak. The end result is a multi-faceted publication that includes information on the following components that are needed to achieve integrated weed management in Australian cotton farming systems:-

a weed identification guide,

integrated weed management,

herbicide resistance,

herbicides and spray guidelines,

roundup ready,

farm hygiene, controlling volunteer cotton and an examination of the interactions of cotton pathogens and insects with weeds,

best bet management guidelines for weeds,

management of problem weeds,

weed management in rotation crops and

appendices on the regional distribution of weeds, a weed species and further reading list with other supporting documents.

Internationally, sticky cotton is a major concern for the textile industry (Hector & Hodkinson 1989). Physiological plant sugars in immature fibres, contaminants from crushed seed and seed coat fragments, grease, oil and pesticide residues are all potential sources. However, all are insignificant compared with honeydew contamination from Bemisia tabaci and Aphis gossypii (Hector & Hodkinson 1989; Ellsworthy et al. 1999a; Hequet & Abidi 2002). The underlying reason is the distribution of the sugars along the fibre. Physiological sugars, grease and oil are usually distributed evenly over the fibre whereas sugars from honeydew tend to be in scattered concentrations (Bruno 1984). In the latter, these sugars lead to uneven yarn which is prone to breaking during weaving and knitting of fabrics (Hequet & Abidi 2002) as well as impeding fibre handling and causing in severe circumstances mill shutdown to clean equipment (Ellsworthy et al. 1999a). A reputation for stickiness has a negative impact on sales, exports and price for cotton from regions suspected of having stickiness. Reductions in the market value of lint due to stickiness are applied regionally and indiscriminately. In Arizona, perceptions regarding stickiness lead to a -5.63c/lb discount relative to Californian cotton (Ellsworthy et al. 1999a).

More than 20 different sugars are excreted in honeydew (Hendrix & Wei 1994) and most are insect rather than plant derived (Tarczynski et al. 1992; Salvucci et al. 1997). The major sugars excreted by A. gossypii are melezitose, sucrose, glucose and fructose while for B. tabaci, there is the additional sugar, trehalulose. Analysis by Hendrix et. al. (1992) of aphid and silverleaf whitefly honeydew from insects feeding on cotton indicated around 40% of total sugars present was melezitose in the aphid honeydew, while silverleaf whitefly honeydew exhibited about 40% trehalulose plus about 17% melezitose.

The two sugars that contribute most to cotton stickiness problems are trehalulose and melezitose (Henneberry et al. 1995, 1996, 1998a, 1998b; Gamble 2001) and both are produced as a result of transglycosylation reactions involving dietary sucrose (Wei et al. 1997). The lint content of both trehalulose and melezitose were quantitatively linked to insect numbers. The composition of honeydew collected directly from Bemisia was found to be virtually identical to that recovered from contaminated lint (Hendrix 1995) and poinsettia (Byrne & Miller 1990). For B. tabaci first and second instars produce less trehalulose than third and fourth instars while adults produce more than nymphs. In contrast, more melezitose was produced by nymphs than adults (Henneberry et al. 1999). While trehalulose and melezitose are significant contributors to sticky cotton the interaction between these, other sugars and cotton stickiness is poorly understood and complicated by the fact that other sugars such as sucrose glucose and fructose occur in both honeydew and cotton lint (Henneberry et al. 1998a).

Using the thermodetector method to measure cotton stickiness (Henneberry et al. 2000) increases in thermodetector sticky cotton counts were closely correlated with increasing numbers of whitefly nymphs and adults. The experience from the USA suggests that the threshold of concern for sticky cotton is indicated by thermodetector measurement ≥ 5 (Frydrych 1986; Brushwood & Perkins 1993). To reach this level, whitefly numbers needed to be ≥ 8.9 adults per leaf or ≥ 3.2 nymphs/cm2 (Henneberry et al. 1998a). This is well below the action thresholds for insect growth regulators (Ellsworthy et al. 1999b). Further, Yee et al. (1997) and Henneberry et al. (1998) indicated that insecticide applications at an average of 10 adults per leaf reduced honeydew production as effectively as applications at 5 adults per leaf. However, standardised sampling protocols, and the relationship between levels of stickiness in the field and problems arising in textile mills are still not well understood (Henneberry et al. 1998a). This is apparent if one plots the data from the USA against thermodetector readings (Henneberry et al. 1998a, 1998b, 2000) (Fig 1). The considerable scatter associated with the correlation underlines the lack of a clear cut decision point with regards to concentrations of trehalulose and melezitose and stickiness.

Little is known about the main predators of emerging pests in Bt cotton. To fill this gap a marking technique using ELISA (enzyme-linked immunosorbent assay), was adapted to assess predation on mirids, Helicoverpa eggs, and cotton aphids. The technique involves marking target pests with rabbit IgG protein and then using ELISA to detect the presence of the protein in predators who may have consumed the pest. The technique was first tested under laboratory conditions, and then applied under field conditions.

Travel grant to attend the 10th International Symposium on Microbial Ecology, 2005

Project US65C: Diversity of VAM fungi in soil health

Travel to participate in the 2005 Beltwide Cotton Conference, January 4th-7th, New Orleans, USA, to visit the USEPA in Washington, DC, USA, and to carry out research within the Centre for Toxicology, Department of Environmental Biology, University of Guelph, Ontario, Canada. Dr Murray attended presented a paper entitled ‘Area-wide management of Helicoverpa spp. in an Australian mixed cropping agroecosystem’.

Travel to attend the 12th Cotton Conference, Gold Coast, August 2004. Abstract presented as a poster at the conference.

Our new project on studying Thielaviopsis basicola-cotton interactions was presented in this conference series for the first time. I was invited by the conference organisers to present this topic in a poster and to include a summary in the conference proceedings. This hopefully enhanced the recognition of the project by other cotton researchers and industry and possibly enhanced collaborations with other researchers working on cotton disease.

In addition, I enhanced my knowledge on the current status of cotton in Australia, the needs of the industry and what other researchers are working on.