Chemicals Are Creating Frightening New Superweeds. The 'Solution'? More Chemicals

American farmers are using more chemicals than ever to kill them...but they keep coming back.

Ragweed. (Photo: Getty Images)

Feb 20, 2014· 3 MIN READ
Clare Leschin-Hoar's stories on seafood and food politics have appeared in Scientific American, Eating Well and elsewhere.

Palmer amaranth is the perfect weed. When the weather is hot and dry, it can grow three inches a day, choking fields of soybean and cotton. Give it two weeks, and the seed, which starts out about the size of the period at the end of this sentence, will become an eight-inch nightmare of a plant.

Palmer amaranth, also known as pigweed, has become herbicide-resistant and is exactly the kind of “superweed” that keeps farmers and weed specialists like Larry Steckel, Ph.D., of the University of Tennessee up at night.

“Pigweed has been the game changer,” he says. “We’ve been dealing with it for five years here.”

They’re dealing with it by creating a layer cake of herbicides that include glyphosate, dicamba, atrazine, gramoxone, 2,4-D, and more, spread on fields at precise times. It’s a complicated chemical recipe, depending on what weed is being targeted. It can start with an application of herbicide before planting. Another right after. A few weeks later, just as the weeds are emerging, a different application may be called for. Sometimes it needs to be timed with rain forecasts. There’s new evidence that even the time of day an herbicide is applied can make a difference. What’s clear is our arsenal to deal with resistant weeds is becoming less effective.

“We’re running out of herbicides,” says Steckel. “There hasn’t been a new one on the market in 25 to 30 years. No wonder we’ve developed resistance. It’s like antibiotics. We’re losing the effective ones. For some of these crops, it’s coming to the point where you can question if they can still be viably grown.”

The weed problem is spreading. Today, nearly every state has an herbicide-resistant species. There’s pigweed, horseweed, ragweed, Italian ryegrass, common waterhemp, and dozens more. If we look at glyphosate resistance specifically, Steckel says there are now 14 documented species in the U.S. (Here’s an interactive map if you’d like to see what’s been documented in your state.)

In 2012, Washington State University research professor Charles Benbrook found that the more superweeds spread across the U.S., the more chemicals farmers applied to farmland to contain them. A lot more.

In 1999, growers used 1.5 million pounds of herbicides to control weeds. In 2011, that number had swelled to 90 million pounds. But the efforts seem increasingly futile.

By 2012, a survey found, nearly half of U.S. farmers said they had glyphosate-resistant weeds on their farm, meaning the weeds had reached 61.2 million acres of American farmland. Benbrook says he suspects that number would top 100 million acres today.

“Since then, it’s gotten way worse,” says Benbrook. “It’s an extremely serious situation. We’ve gone from two applications of glyphosate, one of the safest herbicides on the market, to seven or eight applications of five different herbicides, include two of the most dangerous. This is what farmers are doing, and it’s a doubling or tripling of the costs to farmers.”

In Tennessee, Steckel says farmers are spending nearly $60 an acre on herbicides.

“No farmer wants to spray an herbicide. They’re trying to be more sustainable and cut down on herbicide costs, but it’s not easy. I had one farmer put his costs on a spreadsheet. From 2006 to 2013, his fertilizer costs went up 40 percent. Seed costs went up 50 percent, and herbicide costs went up 250 percent during that time period, and that’s typical for most of our growers,” he says.

Biotech proponents say it isn’t a GMO problem—it’s an herbicide problem, and to a degree they’re right. Superweeds have found their way into non-GMO orchards and grape, wheat, and other fields. But the amount of American farmland devoted to genetically engineered crops such as corn, soy, and cotton, relies heavily on a single herbicide—glyphosate—and that figure continues to climb. In 2012, nearly 70 million hectares of G.E. crops were planted in the U.S., up from 64 million hectares just three years earlier. And glyphosate-resistant weeds continue to grow with it.

That’s prompted seed companies, such as Monsanto, to expand weed-management incentive programs for growers. The idea is to rotate the families of chemicals used on crops such as cotton and soybeans, to better control weeds. Those incentive plans also come with cash.

“They’re paying $1 to $2 an acre subsidy for farmers to apply an herbicide from another company,” says Benbrook. “Companies like Dow, Pioneer, Monsanto, and Syngenta denied resistance would be a problem and said if it became one, they’d find a way to manage it. That’s extremely irresponsible. There’s no scientific basis to say they can deal with it on 100 million acres of American cropland.”

What happens if we don’t get our superweed problem under control? Steckel says the ramifications could be serious for farmers and our nation’s food-production capabilities. He’s worried we’ll follow Australia’s example, and let the weeds take over.

“In Australia, they just fenced it all off and put cattle on the land. Could you imagine doing that in Iowa? That’s not far off from the reality of where we are,” he says.