Resistance predicted a century ago

An Iowa State University weed scientist says resistance issues have been around for a long time. Mike Owen points out that weed resistance to the herbicide glyphosate is more in the public eye now, but the scientific theory is not new.

"Essentially what we’re talking about is a natural function, one that actually Charles Darwin predicted over a hundred years ago,” said Owen, in an experiment plot north of Ames, Iowa, surrounded by various weed species resistant to glyphosate.

Owen says some situations result in selection pressure caused by incorrect grower management decisions imposed on the crop and the weeds, “and they end up with problems.”

Owen says resistance issues in the Mid-South and Southeast began after resistance was discovered in the Upper Midwest. He says southern management tactics are less complex than weed control tactics in the North.

"Their crop production systems are less diverse, and as a result, those problems that have evolved predominantly in palmer pig weed just escalated much faster than what we’ve seen happen here in Iowa, for example, in the giant ragweed, water hemp or mares tail,” said Owen.

Whatever herbicide technology is used, Owen says growers need to improve diversity and to recognize the risk of overusing any one treatment, regardless of its effectiveness, in a given year.

"We need to recognize that if all you’re going to do is spray one herbicide and you’re going to do that for a number of years, ultimately, inevitably it will fail,” he said.

Owen spoke at a Bayer CropScience-sponsored event referred to as Respect the Rotation.

Source: Brownfield AG News