By MATTHEW WEAVER

Capital Press

Northwest researchers advise farmers to alternate weed management strategies to avoid herbicide tolerance in weeds.

In a recent study, Chuck Benbrook, research professor at Washington State University, found farmers are spending $20 to $30 more per acre for herbicide to deal with resistant weeds.

"Spraying more herbicides is not the solution to the spread of herbicide-resistant weeds," Benbrook said. "It's kind of like pouring gasoline on a fire to put it out."

Particularly in the southeastern U.S., farmers who grow herbicide-tolerant crops like corn, soybeans and cotton have to spray more herbicides to deal with glyphosate-resistant weeds, Benbrook said.

There are now 23 glyphosate-resistant weeds in the U.S., including some of the most widespread and difficult to control, Benbrook said.

Farmers in the Pacific Northwest have mostly been spared because 98 percent of the land is not planted to Roundup Ready crops, but if they become more common, the same problem will occur, Benbrook predicted.

Oregon State University weed science professor Carol Mallory-Smith said the spread of glyphosate-resistant weeds gets overblown in the media as an unstoppable superweed.

"They happen to be resistant to glyphosate, but they can still be controlled," she said.

Mallory-Smith said growers have returned to pre-emergent herbicides and other products they used before. They should use all of the options available instead of overusing one, she said.

Researchers across the U.S. are urging farmers to diversify their weed management from only using glyphosate, Benbrook said. Farmers need to use crop rotation, cover crops and mid-season cultivation along with herbicides.

"If farmers don't depend largely or exclusively on herbicides, there's a much better chance the products they do choose to apply will remain effective for a long period of time," he said.

Benbrook also recommends never spraying the same herbicide on the same field two years in a row.

Online

www.enveurope.com/content/24/1/24/abstract