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PostPosted: Tue Apr 17, 2012 5:35 am 
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A much-used herbicide, which for years has helped farmers throughout the United States increase profits, is losing its effectiveness and forcing producers to spend more and use more chemicals to control the weeds that threaten yields.

"I've gone from budgeting $45 an acre just two years ago to spending more than $100 an acre now to control weeds," said Mississippi farmer John McKee, who grows corn, cotton and soybeans on his 3,300-acre farm in the Delta.

The problem is Roundup, a herbicide introduced in the 1970s, and its partner, Roundup Ready crop seeds, genetically modified to withstand Roundup's active ingredient, glyphosate. In 1996, Monsanto introduced Roundup Ready soybean, soon touted as a game changer.

"It was an extremely valuable and useful tool for the past 15 years," said Bob Scott, extension weed scientist with the University of Arkansas.

The problem now is the weeds that Roundup once controlled are becoming resistant to glyphosate, Scott said.

"It's a very, very serious issue here in the Delta," licensed crop consultant Joe Townsend said. "We're knee-deep in it."

As overuse of antibiotics led to resistant bugs or superbugs, the almost exclusive use of glyphosate led to resistant populations of weeds, such as pigweed and ryegrass, once controlled by the herbicide. Glyphosate-resistant weeds have been identified in Australia, South America and China, according to the International Survey of Herbicide-Resistant Weeds.

To combat resistant weeds, farmers are turning to older methods of weed control — more chemicals and more tillage, which leads to increased rates of soil erosion. "I used so many chemicals last year, it made me silly," McKee said. "We're going backwards 15 years."

Bill Freese, science policy analyst at the Center for Food Safety in Washington, D.C., says the use of more chemicals has real public health implications. "It increases the chances they will get into our food and water."

Weed resistance to herbicides is not new. The problem, Freese says, is it's happening at a much quicker rate. "Because of the use of a single chemical (glyphosate), it's speeding up evolution." Herbicide-resistant crops are "taking us in the wrong direction. It's just not sustainable."

Rick Cole, weed management technical lead at Monsanto, said the company recommends "multiple modes of action," essentially, using more than one chemical, crop rotation and tillage. "I think everybody has learned together. When someone says they're using more chemistry, what we're worried about (is), is it safe? Is it effective?"

On the horizon for Monsanto, Cole said, is Roundup Ready 2 Xtend soybeans, genetically engineered to be resistant to glyphosate and dicamba. Dicamba has been on the market for decades, and Cole says crops let farmers use more than one chemical on weeds.

Bayer CropScience also produces genetically modified seeds resistant to its herbicide, Liberty.

By Kevin Pieper, USA TODAY

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