As Weeds Outsmart The Latest Weedkillers, Farmers Are Running Out Of Easy Options

There was a moment, about 20 years ago, when farmers thought that they'd finally defeated weeds forever. Biotech companies had given them a new weapon: genetically engineered crops that could tolerate doses of the herbicide glyphosate, also known by its trade name, Roundup. Farmers could spray this chemical right over their crops, eliminate the weeds, and the crops were fine.These scientists believed that plants couldn't become immune to Roundup because it required too big of a change in a plant's biology.In 2005, though, Culpepper reported that he'd found some weeds that Roundup could not kill. They were growing in a field in Georgia. And this was not just any weed. It was a kind of monster weed called Palmer amaranth, or pigweed.Over the following years, these glyphosate-resistant pigweeds spread like a plague across America's farmland. They're practically everywhere in the South now and increasingly common in the Midwest."The impact is just unbelievable," Culpepper says. "We've invested over $1.2 billion, just in the cotton industry, for control of glyphosate-resistant Palmer amaranth since we first discovered it."