Diversity the key to protecting critical herbicide
Despite increasing resistance in weeds to glyphosate, the good news is that this vitally important herbicide is still effective on most farms where Australian growers are diversifying their weed control practices.
However, it is at risk where it is being used persistently, Australian Herbicide Resistance Initiative (AHRI) director Stephen Powles told the inaugural Crop Protection Forum in Perth.
“We must diversify glyphosate use to preserve this precious herbicide for future harvests and future generations,” he said.
The forum was held at The University of Western Australia (UWA) and was hosted by the Australian Herbicide Resistance Initiative (AHRI) and Centre for Crop and Disease Management (CCDM).
It presented the latest Grains Research and Development Corporation (GRDC) supported research findings to agronomists and advisers, with the aim of helping them to assist growers in blunting the evolution of pesticide resistance in weeds, pests and diseases.
Professor Powles, who is an international authority on all aspects of herbicide resistance in plants, said the use of glyphosate needed to be diversified with other herbicides and non-herbicide weed control measures, to preserve its effectiveness for the long term.
“As I keep emphasising, diversity is the key and when on a good thing, don’t stick to it,” he said.
Professor Powles described glyphosate as the world’s greatest herbicide, and said that because it was so effective and cheap, it was easy to over-use.
He said the consequences of over-using glyphosate could not be overstated, and that in the United States, glyphosate resistant weeds had caused corn and soybean growers’ herbicide costs to triple.
“An estimated 50 million hectares of the world’s best crop land - including 34 million hectares in the US – is infested with glyphosate resistant weeds, and these weeds are often also resistant to other herbicides – posing a threat to global food production,” Professor Powles said.
GRDC supported surveys in WA and other Australian cropping regions have indicated escalating glyphosate resistance, particularly in annual ryegrass.
Analysis of a targeted (not random) pre-harvest survey focusing on weedy WA grainbelt paddocks - conducted in 2013 by DAFWA - showed that more than 40 per cent of 172 annual ryegrass samples tested had some level of resistance to glyphosate.
Random surveys of WA grainbelt paddocks conducted by AHRI in 2010 found that 7 per cent of 362 samples tested contained annual ryegrass with some level of resistance, up from 1 per cent in 2003.
Further surveys conducted by AHRI in 2010 and 2011 in 239 Roundup Ready® canola paddocks across the WA grainbelt found 3.3 per cent of annual ryegrass samples were glyphosate resistant.
Over the last 15 years, the GRDC has invested funding of about $1 million annually into AHRI, which is a research leader in herbicide resistance and its management in cropping systems.
The GRDC has committed $30 million over five years to the $100 million CCDM – which conducts cutting-edge crop disease research - as part of its long-term bilateral agreement with Curtin University.