Utilising paraquat with a rotating mix of other active ingredients may the be the key to minimising herbicide resistance when doing presowing knockdowns.
This was the message from a leading herbicide resistance researcher at last month's Grains Research and Development Corporation (GRDC) update in Bendigo.
Roberto Busi, of the University of Western Australia, who works on the Australian Herbicide Resistance Initiative (AHRI) said herbicide resistance in broad spectrum knockdown herbicides was one of the Australian grains industry's biggest concerns.
He said reports of plants resistant to both glyphosate, Australia's major presowing herbicide and paraquat, the recommended product to help rotate glyphosate, were growing in Western Australia.
"There have been six reports of ryegrass highly resistant to both products in Western Australia, with the resistant ryegrass infesting fencelines," Dr Busi said.
However, he said there had been promise in trials mixing paraquat with other active ingredients.
"When mixed with a spike from Group 13, 14, 15 and 34 herbicides there was significantly greater efficacy with paraquat," he said.
"Under controlled conditions some paraquat-based treatments delivered 100 per cent efficacy and reversed resistance."
Dr Busi said the findings showed the importance of not relying on a single mode of action for weed control.
"The double knock strategy, using both glyphosate and paraquat, followed by the paraquat mixture significantly increased the control of ryegrass."