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Midwestern farmers wage war against 'superweeds'

Midwestern farmers wage war against 'superweeds'


ELSBERRY • After driving several miles along a winding rural road west of this Mississippi River town, Denny Mertz finds what he’s looking for.

The retired engineer, turned full-time farmer, stops next to a neighbor’s field covered in soybeans — and something sinister.

At first glance, there doesn’t appear to be anything out of the ordinary. Until Mertz points out the yellowish cast infiltrating the deep green of the soybean leaves.

It’s waterhemp, a fast-growing weed that torments Midwestern farmers.

But this isn’t ordinary waterhemp, Mertz says.

Surveying the field, he points to an array of dead weeds, suggesting the tract was sprayed with glyphosate — the generic name for Monsanto’s wildly popular herbicide Roundup. Scattered at his feet are the withered remains of foxtail, lamb’s-quarters, ragweed and mare’s-tail.

But what captures his attention is a dead waterhemp stalk, drooping near the base of a sibling that’s quite alive and waving in the summer breeze.

“This is a classic case,” said Mertz, who’s been farming in the area for three decades. “Some of the plants died. And some of them didn’t.”

The survivors are so-called superweeds, a catchy term for what’s technically known as an herbicide-resistant weed. They’ve been around for decades, really. But they’re getting a lot of attention these days, with farmers increasingly running into aggressive varieties that can’t be killed by the herbicide that revolutionized modern farming.

Weed experts say half the nation’s farmland is dealing with the problem in one form or another. Missouri and Illinois farmers already have encountered half a dozen different species immune to glyphosate. The first came a dozen years ago when resistant mare’s-tail was found in a Missouri field.

It’s a problem that grows worse with each passing year, and is now forcing farmers to change how they manage weeds, after years of spray-it-and-forget-it simplicity. It’s that, or wait for infestations to choke the life, and profits, from fields, robbing corn, soybeans and other crops of the nutrients they need to thrive.

Such may be the fate awaiting the plot Mertz is standing in.

“In a couple of weeks, you’ll come out here and see nothing but waterhemp,” Mertz said. “Come fall, this field will be a mess.”


In many ways, the ongoing conflict between farmers and resistant weeds has its roots in 1996, when Monsanto introduced its Roundup Ready soybeans — a crop genetically modified to be immune to glyphosate. Soybeans were followed by corn, cotton and sugarbeets. The combination was revolutionary, offering farmers the ability to kill everything in a field except for the crop it was designed to protect.

Gone was the need for soil-damaging tillage. Gone was the need for multiple herbicides. Gone was the need to deploy teams of hoe-armed high school students tasked with clearing weeds.

Virtually overnight, farming changed. But with that change came the potential for the emergence of a new era of herbicide-resistant weeds.

According to the U.S. Department of Agriculture, more than 93 percent of the nation’s corn, soybean and cotton crops were grown last year from genetically modified seeds — the majority of them glyphosate-tolerant. Not surprisingly, many farmers now rely almost exclusively on the herbicide to police their fields.

“I hate to use the word ‘lazy,’ but we’ve relaxed a little bit,” said Todd Gibson, a Norborne, Mo., farmer and a director with the Chesterfield-based United Soybean Board. “But it’s more our fault than it is the industry’s.”

The problem comes from using the same herbicide over and over on the same field with the same crop.

As a farmer sprays his fields with glyphosate — or any other herbicide — he’ll eventually run across a plant with natural immunity to the chemical, said Aaron Hager, associate professor and weed specialist at the University of Illinois at Urbana-Champaign.

If that particular plant is allowed to survive, its offspring can carry that same natural resistance. It’s a problem that spreads quickly when dealing with pests like waterhemp — a plant that can release 250,000 seeds and whose pollen can travel up to half a mile.

“We call them fields. But they are really biological systems,” Hager said. “It’s evolution in action.”

Putting a price tag on the problem is difficult, though recent studies suggest glyphosate-resistant weeds can cost soybean farmers nearly $50 an acre, factoring in extra herbicide treatments, yield loss and declining land values. Clearly, soybean farmers are spending more on herbicides — $25.10 per acre in 2012, compared with an inflation-adjusted $16.57 in 2006, according to the USDA.

It’s a sizeable chunk of money when you consider U.S. farmers planted 76 million acres of soybeans in 2013 — 9.4 million in top-producing Illinois and 5.5 million in Missouri.

Pushing farmers away from the over-reliance on glyphosate is increasingly a priority for the industry. Last year, the United Soybean Board launched its Take Action program, designed to educate growers and push them to do more to combat herbicide-resistance. University extension experts are spending much of their time, working with farmers desperate for solutions. And Monsanto, in 2010, started its Roundup Ready-Plus program, which pays incentives to farmers for using competitors’ products at various times during the planting cycle. Last year, 63,000 farmers took part in the program.

“There is no silver bullet for managing herbicide resistance,” said John Combest, Monsanto spokesman. “It’s an issue that’s bigger than one class of chemistry, one company, one geography or one crop.”

Still, there are critics who place the blame for superweeds squarely on the doorstep of Monsanto and its peers.

The Union of Concerned Scientists, which opposes the use of herbicides except in the case of emergencies, says the aggressive marketing of glyphosate as a cure-all is responsible for the rapid spread of resistant weeds.

“If it was your intention to create these weeds as quickly as possible, you’d do exactly what we’ve been doing,” said Ricardo Salvador, director of the organization’s food and environment program.


In Lewis Carroll’s book “Through the Looking Glass,” young Alice finds herself in a variety of logic-defying adventures in Wonderland, including one in which she’s running, but going nowhere. This seeming contradiction prompts a complaint from Alice to her companion, the Red Queen.

And it draws this answer: “Now, here, you see, it takes all the running you can do, to keep in the same place. If you want to get somewhere else, you must run at least twice as fast as that!”

It’s a passage used by biologist Leigh Van Valen, who died in 2010, in developing what’s known as the Red Queen Hypothesis. It’s an idea, famous is evolutionary circles, that explains the way a species must constantly evolve to cope with predators and avoid extinction.

And it’s how Jessica Shade, director of science programs for the Organic Center, frames the battle between herbicide producers and the weeds they want to control.

With glyphosate losing its potency, those companies are even now on the brink of introducing new herbicide-seed pairings.

Monsanto scientists are working on soybeans resistant to Dicamba and glyphosate, and cotton that’s resistant to those two plus glufosinate, while Dow AgroSciences is in the final stages of a new corn seed immune both to glyphosate and 2,4-D, which critics note is one of the ingredients of the toxic cocktail known as Agent Orange. The cotton and corn seeds are expected to reach the market in 2015, followed by the soybeans in 2016.

While weed-challenged farmers may be eager to get their hands on these new tools, Shade and others worry over what they see as a chemical arms race — using ever stronger chemicals — that threatens the nation’s food supply.

“They’re just going to have to keep bringing out bigger guns,” Shade said. “It’s a pretty scary path to think about.”

It’s a characterization Monsanto is uncomfortable with, noting that Dicamba is commonly found on farms and has been used on residential lawns for two decades.

“It has a long history of safe use,” Combest said.

Most agree, though, that it will take more than simply adding new herbicide options to the weed-fighting arsenal. Some see a diverse mix of herbicides and frequent crop rotation as one answer.

But others say it’s more likely farmers will be forced to revisit some of the strategies retired in the 1990s. It could mean more hoeing of fields, more tillage, and planting of cover crops to keep fields blanketed and less hospitable to weeds.

“I don’t think we are going to find the solution to the resistance in the bottom of a jug,” said Kevin Bradley, an associate professor and weed expert at the University of Missouri-Columbia. “We have to go back to the way we used to think about weed control.”

It doesn’t help matters that there is a relatively new menace spreading north and threatening Midwestern fields.

Palmer amaranth is an aggressive, fast-breeding weed that can grow up to 10 feet high, with stalks thick enough to damage harvesting equipment. It’s a plant that’s been described as “waterhemp on steroids” or “a superweed before it became herbicide-resistant.”

And now that there are varieties of the plant with glyphosate resistance, academics such as Hager, from the U of I, are warning farmers to be vigilant. A single weed in a field is too many, they say.

“There is no acceptable level of Palmer infestation,” he said. “It is a species that has, quite literally, put farmers out of business.”

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Timothy Barker is a reporter for the St. Louis Post-Dispatch.

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