PAOLA, Kansas (Reuters) - Farmer Mark Nelson bends down and yanks a four-foot-tall weed from his northeast Kansas soybean field. The "waterhemp" towers above his beans, sucking up the soil moisture and nutrients his beans need to grow well and reducing the ultimate yield. As he crumples the flowering end of the weed in his hand, Nelson grimaces.
"When we harvest this field, these waterhemp seeds will spread all over kingdom come," he said.
Nelson's struggle to control crop-choking weeds is being repeated all over America's farmland. An estimated 11 million acres are infested with "super weeds," some of which grow several inches in a day and defy even multiple dousings of the world's top-selling herbicide, Roundup, whose active ingredient is glyphosate.
The problem's gradual emergence has masked its growing menace. Now, however, it is becoming too big to ignore. The super weeds boost costs and cut crop yields for U.S. farmers starting their fall harvest this month. And their use of more herbicides to fight the weeds is sparking environmental concerns.
With food prices near record highs and a growing population straining global grain supplies, the world cannot afford diminished crop production, nor added environmental problems.
"I'm convinced that this is a big problem," said Dave Mortensen, professor of weed and applied plant ecology at Penn State University, who has been helping lobby members of Congress about the implications of weed resistance.
"Most of the public doesn't know because the industry is calling the shots on how this should be spun," Mortensen said.
Last month, representatives from the U.S. Environmental Protection Agency, the Department of Agriculture and the Weed Science Society of America toured the Midwest crop belt to see for themselves the impact of rising weed resistance.
"It is only going to get worse," said Lee Van Wychen, director of science policy at the Weed Science Society of America.
MONSANTO ON THE FRONT LINE
At the heart of the matter is Monsanto Co, the world's biggest seed company and the maker of Roundup. Monsanto has made billions of dollars and revolutionized row crop agriculture through sales of Roundup and "Roundup Ready" crops genetically modified to tolerate treatment with Roundup.
The Roundup Ready system has helped farmers grow more corn, soybeans, cotton and other crops while reducing detrimental soil tillage practices, killing weeds easily and cheaply.
But the system has also encouraged farmers to alter time-honored crop rotation practices and the mix of herbicides that previously had kept weeds in check.
And now, farmers are finding that rampant weed resistance is setting them back - making it harder to keep growing corn year in and year out, even when rotating it occasionally with soybeans. Farmers also have to change their mix and volume of chemicals, making farming more costly.
For Monsanto, it spells a threat to the company's market strength as rivals smell an opportunity and are racing to introduce alternatives for Roundup and Roundup Ready seeds.
"You've kind of been in a Roundup Ready era," said Tom Wiltrout, a global strategy leader at Dow AgroSciences, which is introducing an herbicide and seed system called Enlist as an alternative to Roundup.
"This just allows us to candidly get out from the Monsanto story," he said.