Annual ryegrass with herbicide resistance is now common in southern NSW, according to research recently completed by the EH Graham Centre for Agricultural Innovation at Wagga Wagga.
Researchers at the Graham Centre, John Broster and Eric Koetz, have found high levels of resistance in ryegrass to widely used herbicides in studies conducted from Dubbo in the north of the State, to the Victorian border in the south, and east west between the Hume and Newell highways.
Professor Deirdre Lemerle, director of the Graham Centre, said these findings showed a large increase since the last thorough survey was conducted in 1991.
"Now around 80pc of paddocks surveyed in 2007 had significant levels of resistance to Group A 'fops' herbicides, while resistance to Group A 'dims' was in 20pc of fields," Prof Lemerle said.
"Levels of resistance to Group B ‘SU’ and ‘imi’ herbicides are in 65-70pc of paddocks.
"However, resistance to simazine (Group C) and trifluralin (Group D) was in less than 10pc of paddocks."
Professor Lemerle said in 1991, only 10-15pc of paddocks had ryegrass with resistance to Group A ‘fop’ and Group B ‘SU’ herbicides.
"These high levels of resistance, now present in southern NSW, reinforce the importance of developing new non-chemical weed control techniques into our weed management strategies," she said.
The research is part of a larger survey across the wheat-belt, funded by the Grains Research and Development Corporation.
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