The Australian Herbicide Resistance Initiative (AHRI) has conducted its most comprehensive survey of herbicide resistance in the Western Australian grainbelt.
Funded by the Grains Research and Development Corporation (GRDC), the survey collected samples from a greater variety of weed species compared with previous studies.
AHRI senior researcher Mechelle Owen and colleagues travelled 15,000km in six weeks before the 2010 harvest collecting mature seeds from five weed species.
Weed seeds were collected from 466 paddocks throughout the grainbelt and included 365 samples of annual ryegrass, 128 samples of wild oats, 91 samples of brome grass, 96 samples of wild radish and 46 samples of barley grass.
Ms Owen said that after the weed samples were screened, AHRI would communicate with growers involved to help understand selection pressures or cropping histories that may have led to herbicide resistance identified in the samples.
She said screening of the weed seeds would take place over the next two years, and results from tests of wild radish and ryegrass samples could be available at the end of 2011.
Ms Owen said the analysis would compare changes in resistance levels since previous surveys, and identify any cases of resistance to new herbicides such as Velocity® which is used to control wild radish.
“Previous surveys by AHRI have included a study of ryegrass and wild radish in 1999 and 2003, and a survey of wild oats in 2005,” she said.
“Brome grass and barley grass have been included in the 2010 survey because growers are reporting increasing problems controlling these weeds, particularly brome grass.”
The new survey will also reveal if glyphosate, clethodim (Select®) and trifluralin resistance levels are increasing in WA.
“The 2003 survey by AHRI found developing levels of resistance in annual ryegrass to clethodim and trifluralin,” Ms Owen said.
“We expect the new survey will confirm that levels of resistance to these chemicals have increased and that resistance has spread to new areas of the grainbelt.”
Ms Owen said some growers may not have carried out their normal spraying programs in 2010 due to the poor season, and the survey would take this in to account.
AHRI, located in the School of Plant Biology in the Faculty of Natural and Agricultural Sciences at The University of Western Australia (UWA), is a research leader in herbicide resistance in Australia’s broadacre cropping industry.
Growers can obtain information on integrated weed management and herbicide resistance at AHRI’s website www.ahri.uwa.edu.au and GRDC’s Weedlinks website at www.grdc.com.au/weedlinks.
For more information about the survey, contact Mechelle Owen on (08) 6488 1512 or mechelle.owen@uwa.edu.au
