Disease-causing bacteria isn’t the only place where humans are fighting a losing battle against rapid evolution: Farmers across the country are increasingly finding it difficult to kill “super weeds” as they become resistant to the most popular herbicides.
When “Roundup ready” crops became popular in the mid 1990s, farmers were enamored with the genetically-modified seeds built to withstand glyphosate, the active ingredient in Roundup, the most popular commercial weed killer. But after years of constant exposure, certain invasive plants have also developed a resistance, leading farmers to use more of the chemical. In some cases, the weeds have grown completely tolerant to the chemical, giving farmers fits.
“I was talking to a farmer from Arkansas and he’s got weeds that are now eight feet tall, they’re the diameter of my wrist, and they can stop a combine in its tracks,” says Gary Hirshberg, chairman of Just Label It, an organization fighting for mandatory labeling of genetically modified foods. “The only way they can stop them is to go in there with machetes and hack them out.”
The problem is most pronounced in the southeast where farmers have been growing “Roundup ready,” cotton for years, according to Charles Benbrook, a Washington State University researcher who studies herbicide use. Farmers who grow genetically modified crops use about 25 percent more herbicides than farmers who use traditional seeds, he says. It’s no different than the overuse of antibiotics that has led to resistance from bugs such as gonorrhea in the past year.
“It’s very much the same dynamic in play. By genetically altering corn, soybeans, and cotton so they can be sprayed throughout the growing season, farmers are now spraying their fields three times a season,” he says. “You’re exposing the weed populations to the same herbicide active ingredient three times a year.”
Inevitably, some of the weeds are able to survive several courses of Roundup and pass their resistance on to the next generation, he says.