Western Australia
May 23, 2014
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Research supported by the GRDC RCSN initiative has identified best practice herbicide management for wild radish with multiple herbicide resistance.
Taking action against wild radish early in the growing season is one of the keys to achieving successful control of the problematic weed, advise Western Australian weed authorities.
Wild radish causes severe crop yield losses or forced non-crop phases if uncontrolled and has developed multiple herbicide group resistance, most recently to glyphosate.
Research conducted in the Northern Agricultural Region and supported by the Grains Research and Development Corporation (GRDC) Regional Cropping Solutions Networks (RCSNs) initiative has identified best practice herbicide management for wild radish with multiple herbicide resistance.
Trials were conducted by then Department of Agriculture and Food weeds researcher and now Australian Herbicide Resistance Initiative (AHRI) and Planfarm consultant Peter Newman (in 2012) and Crop Circle Consulting agronomist Grant Thompson (in 2013).
“The trials found that best practice revolved around early spraying of small plants (about the size of the top of a beer can) with excellent application (including adequate water rates) – followed by a quick and timely second spray of a herbicide with a different mode of application,” Mr Newman said.
“The research showed that the whole spraying window should be moved forward, with the first spray at the 1.5 to two-leaf stage, which is earlier than previously recommended.
“Using a two-spray strategy significantly improved weed control efficacy and grain yields – by 0.5 to 1t/ha at some sites – compared with using one late application when wild radish density was high.
“Many WA growers will now, or soon, have wild radish in paddocks at the right size to receive the first spray application.”
Mr Thompson said the trials were successful in finding alternative options to kill wild radish with stacked, or multiple herbicide resistance.
“Newer registered herbicides - such as pyrasulfotole (Group H - eg. Velocity® and Precept®) and pyraflufen-ethyl (Group G - eg. Ecopar®) - are highly effective at controlling wild radish,” he said.
“But there is industry concern about repetitive use of these products and a need to prolong their effectiveness.
“Trials showed that there are other options that can achieve effective wild radish control, particularly if we use an early timing followed by a timely second spray.”
Mr Thompson said two large-scale trials in 2013 at Northampton and Casuarinas, where herbicide tolerant wild radish populations are present, tested the efficacy of ‘two-spray’ herbicide treatment combinations.
“Most treatments achieved 100 per cent weed control when herbicide was applied early, at the 1.5 to two-leaf stage, followed by a spray four weeks later,” he said.
Mr Newman and Mr Thompson stressed that non-herbicide tactics are also vital for controlling wild radish.
A paper about the 2013 trials results was delivered by Mr Thompson to Perth’s 2014 WA Agribusiness Crop Updates, supported by the GRDC and DAFWA. It is available at www.giwa.org.au/2014-crop-updates
The GRDC RCSNs initiative aims to help growers get the information they need, when they need it, so they can make good decisions about farming practices. Details about RCSNs are available at www.grdc.com.au/rcsn
Information about sustainable IWM practices is available at www.ahri.uwa.edu.au
Additional information is at www.weedsmart.org.au and www.glyphosateresistance.org.au
Useful GRDC publications include the Ground Cover supplement Herbicide Resistance – Making Herbicides Last at www.grdc.com.au/GCS104, the Herbicide Resistance Fact Sheet www.grdc.com.au/GRDC-FS-HerbicideResistance and the In-Crop Herbicide Use Fact Sheet www.grdc.com.au/GRDC-FS-InCropHerbicideUse
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