Midwest, South battling Roundup-resistant weeds; more genetically designed crops coming

Genetically mutated, seemingly indestructible weeds that are the direct result of overuse of a herbicide are causing headaches for Midwestern and Southern farmers, who are constantly fighting the destructive intruders, which are immune to drought and heat and grow up to six inches in diameter, "thick enough to damage farm equipment," Mike Wines reports for The New York Times. "Botanists call the weed palmer amaranth. But perhaps the most fitting, if less known, name is carelessweed. In barely a decade, it has devastated Southern cotton farms and is poised to wreak havoc in the Midwest — all because farmers got careless." (NYT photo by Daniel Acker: Uprooting a carelessweed)

"Palmer, as farmers nicknamed it, is the most notorious of a growing number of weeds that are immune to the gold standard of herbicides, glyphosate," Wines writes. "Cheap, comparatively safe and deadly to many weeds, glyphosate has been a favorite ever since the Monsanto Co. introduced it under the name Roundup in the mid-1970s. After Monsanto began selling crops genetically engineered to resist glyphosate in the 1990s, the herbicide’s use soared," Wines writes. But overuse of glyphosate opened the door to 16 different glyphosate-resisting genetic mutations.

“There’s no substantive argument about whether the problem’s gotten far worse in this era of genetically resistant crops,” Charles Benbrook, a professor and pesticide expert at Washington State University, told Wines. “The advent of herbicide-tolerant crops made it possible for farmers to load up so much herbicide on one crop that it was inevitable that it would develop resistance.”

"Palmer amaranths seem as if they were designed by nature to outwit herbicides and farmers," Wines writes. "Unlike many weeds, it has male and female versions, increasing genetic diversity — and the chances of a herbicide-resistant mutation — in each new seed. And each plant is astonishingly prolific, producing up to 200,000 seeds in an average field, said Dave Mortensen, a professor of weed and plant ecology at Pennsylvania State University." Mortensen told Wines, “If one out of millions or billions of seeds contains a unique trait that confers resistance to herbicide, it doesn’t take long when a plant is that fecund for it to become the dominant gene.”

"The industry has readied a new barrage of genetically engineered crops that tolerate other weed killers," Wines writes. The Environmental Protection Agency is set to approve plans by Dow AgroSciences to sell soybean seeds that tolerate not only glyphosate, but a much older herbicide, 2,4-D, and a third widely used herbicide, glufosinate. Monsanto hopes to market soybeans and cotton next year that resist dicamba." Experts say the companies are just repeating the history that made palmers resistant to glyphosate, but farmers say it's worth it if it buys them time before they face another wrath of weed infestation. (Read more)