Australia
November 17, 2010
Land managers are on high alert with reports that kilometres of Riverina roadsides may be infested with glyphosate resistant annual ryegrass.
Although not yet confirmed by laboratory tests, field testing with high rates of glyphosate has shown the ryegrass continues to grow unaffected.
An example of glyphosate resistance in annual ryegrass on Riverina roadsides
This comes close on the heels of the first Australian roadside infestation of glyphosate resistant annual ryegrass confirmed in South Australia earlier this year.
It is a timely warning from the Australian Glyphosate Sustainability Working Group that over-reliance on glyphosate across Australia has to stop and a range of weed control and management strategies need to be implemented anywhere glyphosate is used.
According to the Chairman of the Australian Glyphosate Sustainability Working Group, Dr Chris Preston, roadside infestations pose real threats to weed management adjacent to roadsides as seed can be readily moved to clean areas by water, wind and machinery.
The Riverina outbreak was first raised with Neil Durning, an agronomist with AGnVET Services in Wagga Wagga by council contractors late in 2009. He initiated some alternative control methods including a double knock with paraquat and diquat and more recently a spray-topping application with paraquat to minimise seed set whilst awaiting test results to confirm his suspicion of glyphosate resistance.
“When you are driving along and see large clumps of live ryegrass on the side of the road after very high rates of glyphosate have been applied under good conditions, it certainly grabs your attention,” Mr Durning said.
“Glyphosate resistance is a huge concern to my clients and the entry of glyphosate resistant ryegrass into our cropping paddocks from non-crop areas such as fencelines and roadsides will be a major issue. We need to stop its development by alternating control methods and taking the pressure off glyphosate. Most of the roadsides that we suspect have resistant ryegrass have seen intensive use of glyphosate over the past 15 years with at least one application each year.”
Mr Durning would like to commend the Junee Shire council and its contractors for being extremely co-operative and addressing the issue in a responsible and pro-active manner.
Seed is now being collected from surviving plants in the Riverina for laboratory testing. These plants will then be completely destroyed to prevent seed entering the soil seed bank.
Dr Preston says management of roadsides is a complex operation requiring road-user safety, maintenance of the road surface, protection of significant roadside vegetation and prevention of the spread of weeds.
“Meetings are being organised with local government, contractors and the RTA to discuss the problem and plan to implement management strategies to slow the development of glyphosate resistance on roadsides.”
“The risk to farmers with frontage to roadsides where glyphosate resistant weeds are present is substantially reduced if they have already adopted integrated weed management practices and lessened their reliance on glyphosate for weed control,” Dr Preston stresses.
If anyone suspects glyphosate resistant weeds on roadsides, they are urged to contact the relevant council and their state expert, whose contact details are available from the Australian Glyphosate Working Group web site - http://www.glyphosateresistance.org.au/suspect%20glyphosate.htm
The Australian Glyphosate Sustainability Working Group, supported by the Grains Research & Development Corporation (GRDC) and key R&D based crop protection companies with an interest in the sustainability of glyphosate, has a web site with extensive information about glyphosate resistance, including a register of glyphosate resistant weed populations as well as guides and links for management of glyphosate resistance in different industries.
Go to: www.glyphosateresistance.org.au for more information.
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