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Australia finds own problems with herbicide resistance

Ordinarily, Steve Powles would have spent January basking in the sunshine on one of the western beaches of his native Australia.

January is peak summer in the land down under and that’s when Powles, like most of his countrymen, likes to take vacation. But this year he traded warm summer Australian sun and sand for the cold rain and ice of an American winter. Powles, a plant biologist and director of the Western Australia Pesticide Resistance Initiative, is in the United States doing missionary work of a sort, but instead of trying to save souls, he’s trying to save glyphosate.

“Herbicide resistance is a massive problem in Australia,” Powles said during a Syngenta-sponsored media breakfast at the Commodity Classic, held recently in Austin.

Syngenta sponsored Powles’ pilgrimage, during which he visited farms and ag industry events across the country, including Midwestern soybean and grain farmers and Southern cotton growers. He also visited Hawaii.

He says the United States ranks No. 2 on the worst herbicide resistance problem list. But the Americans are gaining and Powles predicts that by 2008 Australia will lose its number one ranking. He aims his message at growers, consultants, industry representatives and even agricultural journalists, encouraging them to take glyphosate resistance seriously and to initiate programs to prolong the herbicide’s efficacy.

Powles identified glyphosate resistance in Australia in 1996 and published the first report on the problem in 1998.

Trouble comes from several directions. A monoculture aids resistance, he says. “In Australia, wheat is our primary crop and we have large farms, 10,000 acres on average.” And most of those acres see years of nothing but wheat. He says some ryegrass species are resistant to every herbicide, even glyphosate. He says glyphosate resistance is not widespread in Australia and the agricultural community is working to prevent loss of the herbicide.

“It is tremendously important to our overall weed control program,” he says.

Adoption of reduced tillage systems and reliance on Roundup or generic glyphosate products for burndown weed control paves the way for resistance to build. He says the1996 introduction of Roundup Ready crops hastened the problem for U.S. growers.

“That was the most rapid adoption ever of agricultural innovation,” he says. “It’s fantastic and of great benefit to farmers. It’s easy, effective and results in clean fields.”

He says U.S. farmers plant a significant number of corn, soybean and cotton acres in Roundup Ready varieties. “Inadequate diversification of weed control systems spells trouble for both U.S. and Australian farmers,” h says. The main difference, for now, is that Australian farmers are sensitive to the problem. “We’re doing everything we can to combat resistance,” he says.

That includes chemical as well as cultural and physical tactics.

Powles says, tongue-in-cheek, that a lot of good and a lot of not so good ideas often flow from the United States to Australia. The reverse is seldom the case, but information about herbicide resistance is an exception.

“In Australia, farmers, consultants, even farm journalists understand the problem,” he says. “That does not seem to be the case with U.S. farmers, consultants and journalists.”

He encouraged reporters to warn farmers and consultants to take the issue seriously and to be sensitive to the ramifications of losing glyphosate. He says Australian farmers have seen other herbicides fail. “They’ve applied herbicides to ryegrass and hoped to see the grass die and it did not,” he says. “We understand how much we need glyphosate. Does the U.S. farmer value it as highly?”

He says the success of Roundup Ready technology has been both a tremendous blessing and a significant responsibility. Economics plays the key role in weed control programs, he says. ‘Farmers stay with their most profitable system.”

In the Midwest that usually means a Roundup Ready corn crop followed by a Roundup Ready soybean crop or continuous cropping of one or the other of those options. In the South, it may mean a Roundup Ready cotton and Roundup Ready corn or soybean rotation.

Growers and consultants have already identified glyphosate resistant weeds in the United States and “it is likely to get worse,” Powles says. “So, does it matter to U.S. farmers?

That depends on whether they believe they have other options, either old or new herbicides, that will do the job just as well. “They don’t. So it is a big deal. We will not, in our lifetime, see a herbicide as good as glyphosate. It is a 1-in-100-year discovery.”

He compares glyphosate to penicillin, developed during World War II and which changed the way doctors treated a number of infections. He says glyphosate is almost a perfect herbicide and has “made a major contribution to world food production. We must be cautious about driving glyphosate to the point of being useless. We will lament the day that happens. The world will not come to an end. We will survive, but we will lament the day. Nothing as good will replace it.”

The key to saving the herbicide, he says, is diversity. “We don’t see enough diversity in weed control systems. If something is good, we need to give it a rest.”

He suggests paraquat or Liberty (Ignite) herbicides as alternatives. “The Liberty Link system is good technology and I don’t understand why it’s not pushed harder,” he says. “I see a lot of opportunities for Liberty Link.”

Preserving glyphosate will find different solutions in different places, he says. “It will be a farm-by-farm, state-by-state and country-by-country effort. Solutions will be different for different areas.”

Powles insists that glyphosate resistance is a crucial issue. “Time is running out. I expect to see a major increase in glyphosate resistant weeds in the next ten years. Farmers have been blinded by the success of Roundup Ready technology. Fortunately, U.S. growers are beginning to recognize the problem.”

He says resistance is the “inevitable consequence of overuse.” The problem is compounded by the lack of alternatives and the short list of chemical manufacturers looking for new products. Powles says when he started looking into resistance some 25 chemical companies were in discovery mode for new products. “Now we have four.”

Chuck Foresman, Technology Brands Manager for Syngenta, says companies have already gathered the low hanging fruit. “We’ve found the easy stuff. We don’t have new modes of action coming along.”

He says it’s important for experts like Powles, who he considers the world’s foremost authority on herbicide resistance, to discuss potential dangers of herbicide overuse and to offer alternatives.

Foresman says Powles’ ability to communicate his experience so non-scientists understand makes him an even better disciple for herbicide stewardship. That’s why Syngenta sponsored Powles’ trip to the States. “We got involved because glyphosate is the best herbicide ever discovered,” he says. “That comes from a company that did not discover it. But we do manufacture glyphosate (Touchdown) so we have a vested interest, too.”

Foresman says product stewardship is paramount to delaying onset of resistance. “We include stewardship recommendations on our label (for Touchdown),” he says. “We recommend farmers rotate not just herbicides but modes of action. We also recommend no more than two applications of glyphosate in corn or soybeans in a two-year period to help delay resistance. We will not stop it but we can delay it.”

He recommends tank mixes with full rates of glyphosate and another herbicide with a different mode of action. He also recommends alternate modes of action for burndown herbicides. “Gramoxone is a good option,” he says.

“We hope to find a better herbicide and a new mode of action. We will see a lot of new herbicides coming out in the next few years but they will have the same or similar modes of action (as those already available).”

Until that new chemistry comes along, growers must practice product stewardship, Powles says, because resistance is not a question of if but when. “This is not a fictitious problem. It’s a fact.”

e-mail: [email protected]

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