Ground Cover North : Ground Cover 069 July-August 2007 - North
VARIETIES MEASURED FOR HERBICIDE TOLERANCE Coordinating variety trials and reporting all results will help provide variety-specific herbicide guidance BY EMMA LEONARD n Crop varieties can differ in their sensitivity to commonly used herbicides and tank mixes. However, on-farm this sensitivity is often masked by increases in grain yield because of reduced weed competition. For the past 15 years, Robert Wheeler and colleagues at the South Australian Research and Development Institute (SARDI) have run herbicide-tolerance trials as part of SA’s variety-testing program. The work has been modelled on a similar, long-running program at Wagga Wagga, NSW, managed by Peter Lockley. In recent years, similar programs have also been established in other states. The evolution of National Variety Trials (NVT), where advanced breeding material is tested across a spread of states, has also encouraged the development of a more collaborative approach to herbicide-tolerance testing. Within herbicide-tolerance trials, grain yield losses of more than 10 per cent to pre-emergent or in-crop applications of some recommended herbicides have been frequently recorded. For example, in alkaline soils in SA, Tamaroi durum wheat has shown sensitivity to pre-plant chlorsulfuron and NorthfieldA lentils to diflufenican. Several barley varieties including Barque and MaritimeA have been shown to be sensitive to the herbicide terbutryn when used at label-recommended rates. “Testing advanced breeding material and new varieties for their sensitivity to pre- and post-emergent herbicides and recommended mixes will help in the development of variety-specific herbicide management packages,” explains Mr Wheeler, who leads the SA varietal herbicide-tolerance project and national coordination. “In South Australia we are testing herbicide sensitivity in a wide range of cereal and pulse crops, while in other states the focus is on cereals or pulses. Most of the research is supported jointly by the GRDC and state agencies, with some industry funding also being provided.” A feature of all the herbicide-tolerance research is the need for testing to be carried out in relatively weed-free conditions, as crop sensitivity to herbicides can be masked by improved yield due to reduced weed/crop competition. In northern region trials this year, more than 45 varieties and advanced lines of wheat and barley are being evaluated against up to 15 herbicide-treatment combinations. Using similar protocols in each region, herbicide treatments are generally applied at label-recommended rates and at a higher rate, which provides an estimate of varietal tolerance and safety margin when compared with untreated controls. Treated plots are compared with the control for colour, stunting, leaf necrosis, tiller and leaf numbers and days to maturity. Results from work in the northern region with combinations of local breeding material and preferred herbicides have shown similar problems of crop sensitivity to some herbicides. However, work by John Churchett and colleagues in the northern region has demonstrated that the same herbicides behave very differently in the northern and southern regions. This indicates a strong environmental influence on herbicide tolerance. “A crop’s sensitivity to a herbicide has not only been found to vary between regions, but also between seasons,” he says. “For example, in very wet years a soluble pre-emergent herbicide such as metribizin or diuron may be leached into the root zone causing damage, which may not be apparent in drier seasons.” Varieties and advanced lines are generally tested for two or more years to validate varietal responses and minimise the influence of season on herbicide tolerance. However, if yield loss has occurred in a single year, this will be reported as a warning. Data from the state-based varietal herbicide-tolerance programs has been widely disseminated in the past. In coming months – for the first time – data from the herbicide-tolerance trials across Australia will be collated and available on the NVT website, www.nvtonline.com.au. GRDC Research Codes DAS00070, DAQ00106, DAW00134, DAN00067, DAV00057 More information: Robert Wheeler, 08 8303 9480, email@example.com Variety trials GROUND COVER JULY -- AUGUST 2007 6 KEY POINTS n Herbicide-tolerance test- ing now coordinated across regions n Consolidated data to be available on NVT website www.nvtonline.com.au Senior researcher John Churchett, of the Queensland Department of Primary Industries and Fisheries, inspects the cereal herbicide-tolerance plots for maturity. Data from all herbicide-tolerance trials will be reported for the first time this year on the NVT website. PHOTO: EMMA LEONARD Worried about your crop? *Contact WFI for full terms and conditions. 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Ground Cover 070 September-October 2007 - North
Ground Cover 068 May-June 2007 - North