Glyphosate resistant ryegrass has been confirmed at four new locations in Australia.

The new populations bring the total number of populations to 44, with 24 of the cases in broadacre cropping.  All are in annual ryegrass.

New populations from New South Wales come from a broadacre chemical fallow, an irrigation channel and a fenceline. The fourth new population comes from a vineyard in South Australia.  

There has been no increase in the number of glyphosate resistant populations in Western Australia.

National Glyphosate Sustainability Working Group chairman Rick Llewellyn said that while the new populations demonstrated the risk of too much reliance on glyphosate, the low number of new populations in broadacre cropping suggested preventative action taken by growers was making a difference.

"It's now 10 years since the first case of resistance to this valuable herbicide was discovered and many people had predicted much higher resistance levels by now," Dr Llewellyn said.

"We believe we are now seeing the positive pay-off from preventative action taken by the many growers who recognized their glyphosate use history had placed them at high risk of resistance and they did something about it.”

Research from the University of Western Australia has shown that the rare nature of glyphosate resistance meant practices such as the double-knock can greatly reduce the likelihood of resistance developing and be a profitable strategy. 

The Glyphosate Sustainability Working Group has produced a guide listing a number of methods to reduce the risk of developing glyphosate resistance.

"The important thing now is for growers who are entering into high risk situations such as no-till or winter fallow to recognise the risks and how they can be reduced - we're clearly seeing that glyphosate resistance is not inevitable," Dr Llewellyn said.

Details of glyphosate resistant populations in Australia are listed on the Australian Glyphosate Resistance Register, compiled by Dr Chris Preston from the Grains Research and Development Corporation (GRDC) supported Weeds CRC. 

The register and information on how resistance can be managed is available from the national Glyphosate Sustainability Working Group (GSWG) website www.weeds.crc.org.au/glyphosate.