Glyphosate resistance worrying

Weed management expert Chris Preston is skeptical about whether glyphosate interferes with crop mineral uptake, but he's in no doubt about the resistance problems that are emerging from injudicious use of a cheap, easy tool.

Annual ryegrass, barnyard, windmill and liverseed grasses, and fleabane, have developed glyphosate-resistant populations, and Dr Preston thinks a sixth plant is about to join the list.

In the United States, the blanket spread of crops genetically modified to be glyphosate resistant and a lax rotation system means that 21 glyphosate-resistant weeds are found across 8.5 million hectares of farmland.

Across the border in Canada, where GM crops have been used for as long and as enthusiastically, there are only two glyphosate-resistant weeds--and the resistant fleabane announced this year may have come north out of the US.

Not surprisingly, Dr Preston wants Australian growers and their suppliers to look to Canada.

"The beauty of Canada is that several different herbicide tolerant canola varieties were introduced at about the same time, and they rotate with cereals. So they put much less pressue on glyphosate than US growers with continuous Roundup Ready cotton and soybeans."

Canadians also use vigorous hybrid varieties that crowd out weeds, further reducing their reliance on herbicides.

Dr Preston thinks Australian growers have realised that they have an issue to deal with; "the question is, what do they do about it?"

That's especially a problem for northern growers who have become hooked on moisture-saving chemical fallows - not coincidentally, also big sources of most weed resistance.

Cultivation is an excellent solution, but presents erosion issues. Alternative chemistry is possible, but it's expensive.

Lack of viable choice is the problem, as it is for US cotton and soy growers. But unless they want to grapple with the resistance challenges testing the US, farmers will have to find another way to create summer fallows.

Source: The Land Farmonline