Herbicides are losing in the battle against 'superweeds'

The winner: Palmer amaranth, better known as pigweed

"Superweeds — that is, weeds that have evolved characteristics that make them more difficult to control as a result of repeatedly using the same management tactic — are rapidly overtaking American commodity farms," H. Claire Brown reports for The New York Times. "By now, it’s clear that weeds are evolving faster than companies are developing new weed killers."

That poses a major threat to global food production. "It’s hard to estimate exactly how much damage has already been wrought by herbicide resistance; the weeds are gaining ground faster than scientists can survey them. But research published in 2016 by the Weed Science Society of America found that uncontrolled weeds could cause tens of billions of dollars of crop losses every year."

Scientists are experimenting with different solutions, but nothing has worked very well yet, Brown reports. More and better herbicides aren't the answer, said Vipan Kumar, a weed scientist from Kansas State University, and growers should not rely so much on them to get rid of weeds, nor pin their hopes on chemical companies inventing a new, more effective one before it's too late. He cites Palmer amaranth, or pigweed, as an example. The notorious weed adapts to new pesticides far more quickly than companies can come up with new ones. And "evidence is mounting that weeds can actually metabolize herbicides, breaking them down before they do their work," Brown reports. "In other words, Palmer amaranth may have evolved resistance to weed killers that have yet to be invented."