Collaborative research in Western Australia has produced the unexpected result that timing, application and using different herbicide groups are more important than product choice for control of the problem weed wild radish.
“We found that if small weeds – the size of the top of a beer can – were sprayed twice with good coverage, some very herbicide resistant wild radish could be killed using a range of herbicide combinations,” researcher Peter Newman said.
“Another key to successful control was using herbicides with different modes of action, which ensured that enough effective chemistry was available to not have to over-rely on any one herbicide group.”
The research was initiated through the Grains Research and Development Corporation (GRDC) Geraldton port zone Regional Cropping Solutions Network (RCSN), after it identified the weed as a major priority for local growers.
Researchers aimed to find new tankmixes as an alternative to using herbicides such as Velocity® (bromoxynil and pyrasulfotole) twice in a growing season.
Over-reliance on these newer herbicides could heighten the risk of wild radish developing resistance to them.
Coordinated by agricultural consultancy Planfarm and the Department of Agriculture and Food (DAFWA), the research was conducted at trial sites containing the worst, hardest-to-kill wild radish populations.
Mr Newman, now communications leader at the Australian Herbicide Resistance Initiative (AHRI), based at Planfarm, said there were many two-spray strategies that provided 100 per cent control of wild radish, but only one, one-spray strategy that provided this level of control.
“Given growers need a diverse range of herbicide options for wild radish control, two sprays are therefore best,” he said.
Mr Newman said there were a number of effective combinations in the trials that used older herbicides as part of the two-spray strategy, and would pave the way for farmers to reduce reliance on newer chemistries.
“One of the implications of the research is that growers can move the whole spraying window forward, avoiding late herbicide sprays that could result in chemical residues in grain,” he said.
Planfarm consultant and agronomist Andrew Sandison said the results also highlighted the importance of using full label water rates and boosting spray capacity, where possible, with existing or new machinery.
“Boosting spray capacity can result in more effective weed control and save time and money,” he said.
“To increase the efficiency of existing machinery, the key is to have chemical on-hand early, potentially employ extra staff and use nurse tanks to speed the application process.”
Mr Sandison and Mr Newman stressed that chemical control methods should be used in combination with non-herbicide weed control practices.
The GRDC RCSN initiative aims to help growers get the information they need, when they need it, so they can make good decisions about farming practices.
As well as initiating smaller projects, RCSNs feed issues into the standard GRDC investment process which leads to bigger projects.
More information about the RCSNs can be found at www.grdc.com.au/rcsn, or by contacting RCSN coordinators Julianne Hill (Kwinana west, Kwinana east, Albany and Esperance port zones) on 0407 261 607; or Cameron Weeks (Geraldton port zone) on 0427 006 944.
More details about the RCSN wild radish research results will be contained in an article in the May-June edition of the GRDC magazine Ground Cover, which will be available from www.grdc.com.au/groundcover.
May-June Ground Cover will also contain the supplement Making Herbicides Last.
To find out more about Australian research programs targeting herbicide resistance and resistance management to encourage sustainable cropping systems, visit the AHRI website at www.ahri.uwa.edu.au
For information on herbicide sustainability and harvest weed seed control practices, visit the WeedSmart information hub at www.weedsmart.org.au
PHOTO CAPTION: Collaborative research initiated through the Geraldton port zone RCSN has found that timing and application are more important than product choice for control of wild radish. Photo courtesy of DAFWA.
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