[Stock & Land, 28 Jan, 2010: p. 20] A row has erupted over claims that genetically modified glyphosate tolerant crops are accelerating the development of herbicide-tolerant "superweeds". Self-described food safety group and anti-GM campaigners MADGE Australia earlier in the month released a statement quoting a report from the American scientific magazine Proceedings of the National Academy of Science (PNAS) that there had been an increased instance of glyphosate resistant weeds following the uptake of GM technology.
However, the dean of Melbourne University’s Department of Land and Food Resources Rick Roush, a committed proponent of GM, said the group was mistaken in attributing the rise of herbicide resistant weeds on the use of GM. "Herbicide-resistant weeds are not new, nor are they superweeds’," he said.
He said while the strain of resistance described in the PNAS paper was "fascinating" scientifically, it did not support the thesis that GM led to herbicide-tolerant weeds.
"Australian cotton growers have grown Roundup Ready cotton for over a decade, and despite intensive searches, no glyphosate resistant weeds have been found," he said.
However, MADGE Australia researcher Madeleine Love said the excessive use of Roundup Ready technology led to increased pressure on glyphosate, the most used herbicide in Australian broadacre farming.
"GM crops, designed to be sprayed with glyphosate (Roundup), are making that herbicide useless for both GM and conventional farmers." She said that the PNAS findings showed that it did not matter how good a chemical rotation a farmer used, natural resistance would evolve in GM crops.
However, Dr Roush said that herbicide tolerance. while a serious issue, was a separate topic. "Resistance to glyphosate in annual ryegrass, for example, has been described in Australia and California since the 1990s, and is now widespread but still completely independent of GM crops," he said.
He said the answer in managing herbicide came back to chemical rotations.
"The consistent message from weed scientists is that to avoid resistance, we must all practice a diversity of weed management practices, and avoid dependence on any one herbicide. A newly described resistance mechanism does not alter that message." Dr Roush claimed MADGE Australia was ignoring strong data of the benefits of GM crops.
"In attacking GM crops, MADGE has continued to ignore the enormous human health and environmental benefits of GM crops around the world." He said that a far bigger threat existed in more familiar territory.
"As the former director of the Weeds Co-operative Research Centre (1998-2003), I must note that if there are any superweeds in Australia, they are escaped garden plants like Paterson’s Curse and blackberries."