AUSTRALIAN farmers need to manage glyphosate rotations carefully to avoid the problems emerging in the United States, where glyphosate tolerant genetically modified (GM) crops have led to an over-reliance on the cheap and popular herbicide.
As a result of the over-use of glyphosate, there has been a string of resistance problems, causing chaos among the farming community.
Opinion is divided as to how well set up Australia is to manage the inevitable problems with glyphosate resistance, which had already emerged on a small scale prior to the introduction of commercial GM crops at the beginning of 2008.
Chris Preston, weed management specialist at the University of Adelaide, said the US problems, which include large scale resistance in weeds such as horse weed and giant rag weed, have been caused by misuse of glyphosate.
“If you end up with a Roundup (the major commercial form of glyphosate) only system, then you are going to run into resistance problems, whether you are growing GM crops or not.”
Dr Preston said he believed there was more awareness of the potential for glyphosate resistance in Australia now than when GM crops were introduced to the US about 15 years ago.
“We have already had some problems with resistance in various farming systems, such as in chemical fallows, vineyards and along fencelines, prior to the introduction of GM, and I think growers will be attempting to do things differently to the US.”
Dr Preston acknowledged that this season Australian farmers, confronted with tight budgets, would be tempted to use low cost glyphosate products for control, rather than other, more expensive options.
“We will have farmers looking for the cheapest options, and they are not going to want to spend extra money on the other chemicals like they should, but the message is that it is not worth it, and that the entire industry will end up with a problem if glyphosate is abused.”
Rupanyup, Victoria, GM canola producer Andrew Weidemann said he was confident that increased exposure to resistance issues would see Australian farmers better prepared than their US counterparts to manage glyphosate.
“I guess if there has been a silver lining from the delay in the introduction of GM technology here in Australia, it has been the chance to observe what problems have come up in other countries and how they deal with them.”
Mr Weidemann was confident there was a suite of chemical and management options that would allow Roundup to remain effective.
“No doubt resistance is an issue, and we have to manage our chemical and crop rotations carefully, but there are the options there, such as atrazine or Gramoxone (bipyridyl) chemical products or management techniques such as hay cutting, crop topping or green manuring paddocks to stop seed set.”
Mr Weidemann also foresaw livestock playing an important role in rotations, given their current high value.
“Given that we have seen the profits you can make by having a paddock out of crop and used for livestock, I think we may see more livestock in the rotation and a move away from really strict no-till principles.
“Overall, the simple message is that one mode of weed control action will always fail – I’d encourage people, whether they’re growing GM or not, to have a look at Monsanto’s Roundup resistance risk program, just to see whether they are using glyphosate correctly or whether they are at risk of resistance problems.”
Julie Newman, of the Network of Concerned Farmers (NCF) is more pessimistic about Aussie farmers’ patterns of usage.
“It’s not true that we won’t abuse glyphosate, farmers will look for the best economic solution for them, especially this season with limited cash flow, and if there is a short-cut there, they will take it.”
Mrs Newman said that Monsanto’s resistance monitoring programs were only voluntary, and doubted whether GM producers would be willing to spend more on chemicals rather than using the cheaper glyphosate option.
She also said there were few chemical options to replace glyphosate in system.
“There is already resistance to the atrazines and simazines, that can be used in triazine tolerant (TT) canola varieties, while Gramoxone is a very potent product.
“We run a spray contracting business, and quite often Gramoxone is the one chemical product farmers are reluctant to apply.
“Other management options, such as hay cutting, aren’t an option in every district, so we are going to end up going back to cultivation in many areas, which does away with many of the so-called environmental benefits of GM.”
She said GM canola altered the natural course of a rotation.
“Even though the chemical options are declining, canola is supposed to be a break crop, and a chance to have a break from glyphosate in the chemical rotation, now we have a situation where you are trying to use the chemical you need to have a break from.”
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