We’ve A Super Weed, Super Weed, We’re Super-Weedy, Yow

William Neuman and Andrew Pollack at NYT:

Just as the heavy use of antibiotics contributed to the rise of drug-resistant supergerms, American farmers’ near-ubiquitous use of the weedkiller Roundup has led to the rapid growth of tenacious new superweeds.

To fight them, Mr. Anderson and farmers throughout the East, Midwest and South are being forced to spray fields with more toxic herbicides, pull weeds by hand and return to more labor-intensive methods like regular plowing.

“We’re back to where we were 20 years ago,” said Mr. Anderson, who will plow about one-third of his 3,000 acres of soybean fields this spring, more than he has in years. “We’re trying to find out what works.”

Farm experts say that such efforts could lead to higher food prices, lower crop yields, rising farm costs and more pollution of land and water.

“It is the single largest threat to production agriculture that we have ever seen,” said Andrew Wargo III, the president of the Arkansas Association of Conservation Districts.

The first resistant species to pose a serious threat to agriculture was spotted in a Delaware soybean field in 2000. Since then, the problem has spread, with 10 resistant species in at least 22 states infesting millions of acres, predominantly soybeans, cotton and corn.

The superweeds could temper American agriculture’s enthusiasm for some genetically modified crops. Soybeans, corn and cotton that are engineered to survive spraying with Roundup have become standard in American fields. However, if Roundup doesn’t kill the weeds, farmers have little incentive to spend the extra money for the special seeds.

Roundup — originally made by Monsanto but now also sold by others under the generic name glyphosate — has been little short of a miracle chemical for farmers. It kills a broad spectrum of weeds, is easy and safe to work with, and breaks down quickly, reducing its environmental impact.

Sales took off in the late 1990s, after Monsanto created its brand of Roundup Ready crops that were genetically modified to tolerate the chemical, allowing farmers to spray their fields to kill the weeds while leaving the crop unharmed. Today, Roundup Ready crops account for about 90 percent of the soybeans and 70 percent of the corn and cotton grown in the United States.

But farmers sprayed so much Roundup that weeds quickly evolved to survive it. “What we’re talking about here is Darwinian evolution in fast-forward,” Mike Owen, a weed scientist at Iowa State University, said.

Some Room For Debate at NYT:

American farmers’ broad use of the weedkiller glyphosphate — particularly Roundup, which was originally made by Monsanto — has led to the rapid growth in recent years of herbicide-resistant weeds. To fight them, farmers are being forced to spray fields with more toxic herbicides, pull weeds by hand and return to more labor-intensive methods like regular plowing.

What should farmers do about these superweeds? What does the problem mean for agriculture in the U.S.?

Michael D.K. Owen:

The solution to the problem for farmers who have yet to cause the evolution of glyphosate-resistant weeds is to adopt a more diverse weed management program that includes tactics other than glyphosate. By altering the selection pressure on the weeds, glyphosate resistance will be slow to evolve.

For those increasing number of farmers who have glyphosate-resistant weeds, the solution is similar but more difficult: adopt alternative tactics that will control those weeds. Of course, often these weeds have also evolved resistance to other herbicides, which, again, is attributed to the historic use of one herbicide as the sole management tactic. In this case, weed control may be more challenging and costly.

Michael Pollen at Room For Debate:

A few lessons may be drawn from this story:

1. A product like Roundup Ready soy is not, as Monsanto likes to claim, “sustainable.” Like any such industrial approach to an agronomic problem — like any pesticide or herbicide — this one is only temporary, and destroys the conditions on which it depends. Lucky for Monsanto, the effectiveness of Roundup lasted almost exactly as long as its patent protection.

2. Genetically modified crops are not, as Monsanto suggests, a shiny new paradigm. This is the same-old pesticide treadmill, in which the farmer gets hooked on a chemical fix that needs to be upgraded every few years as it loses its effectiveness.

3. Monocultures are inherently precarious. The very success of Roundup Ready crops have been their undoing, since so many acres were planted with the same seed, and doused with the same chemical, resistance came quickly. Resilience, and long-term sustainability, comes from diversifying fields, not planting them all to the same kind of seed.

Marion Nestle at The Atlantic:

Yesterday’s New York Times ran an article disclosing the rise and spread across the United States of “superweeds” that have developed resistance to the herbicide Roundup. The article comes with a nifty interactive timeline map charting the spread of Roundup resistance into at least 10 species of weeds in 22 states. Uh oh.

Roundup is Monsanto’s clever way to encourage use of genetically modified (GM) crops. The company bioengineers the crops to resist Roundup. Farmers can dump Roundup on the soil or plants. In theory, only the GM crops will survive and farmers won’t have to use a lot of more toxic herbicides. In practice, this won’t work if weeds develop Roundup resistance and flourish too. Then farmers have to go back to conventional herbicides to kill the Roundup-resistant weeds.

In 1996, Jane Rissler and Margaret Mellon of the Union of Concerned Scientists, wrote “The Ecological Risks of Engineered Crops” (based on a report they wrote in 1993). In it, they predicted that widespread planting of GM crops would produce selection pressures for Roundup-resistant weeds. These would be difficult and expensive to control.

At the time, and until very recently, Monsanto, the maker of Roundup, dismissed this idea as “hypothetical.”

I know this because in the mid-1990s, I traveled to Monsanto headquarters in St. Louis to talk to company scientists and officials about the need for transparent labeling of GM foods. Officials told me that Roundup had been used on plants for 70 years with only minimal signs of resistance, and it was absurd to think that resistance would become a problem. I pointed out that Roundup resistance is a “point” mutation, one that requires minimal changes in the genetic makeup of a weed.

Carl Zimmer at Discover:

Neuman and Pollack left the story of this fast-forward evolution at that–but it’s actually a fascinating tale. A century ago, Melander could only study natural selection by observing which insects lived and died. Today, scientists can pop the lid off the genetic toolbox that insects and weeds use to resist chemicals that were once thought irresistible. Stephen Powles, a scientist at the University of Western Australia, has been studying the evolution of Roundup resistance for some years now, and he’s co-authored a new review that surveys what we know now about it.

What’s striking is how many different ways weeds have found to overcome the chemical. Scientists had thought that Roundup was invincible in part because the enzyme it attacks is pretty much the same in all plants. That uniformity suggests that plants can’t tolerate mutations to it; mutations must change its shape so that it doesn’t work and the plant dies. But it turns out that many populations of ryegrass and goosegrass have independently stumbled across one mutation that can change a single amino acid in the enzyme. The plant can still survive with this altered enzyme. And Roundup has a hard time attacking it thanks to its different shape.

Another way weeds fight off Roundup is through sheer numbers. Earlier this year an international team of scientists reported their discovery of how Palmer amaranth resists glyphosate. The plants make the ordinary, vulnerable form of the enzyme. But the scientists discovered that they have many extra copies of the gene for the enzyme–up to 160 extra copies, in fact. All those extra genes make extra copies of the enzyme. While the glyphosate may knock out some of the enzymes in the Palmer amaranth, the plants make so many more enzymes that they can go on growing.

It’s also possible for weeds to evolve resistance to Roundup without any change whatsoever to the enzyme Roundup attacks. When farmers spread Roundup on plants, the chemical spreads swiftly from the leaves all the way down the stems to the roots. This fast, widespread movement helps make Roundup so deadly. It turns out that some species of horseweed and other weeds have evolved a way to block the spread. Scientists don’t yet know how they manage this. It’s possible that cells in the leaves suck the Roundup in through their membranes and then tuck it away in safe little chambers where they can’t cause harm. However they do it, the weeds can continue to grow with their normal enzymes.

What makes the evolution of Roundup resistance all the more dangerous is how it doesn’t respect species barriers. Scientists have found evidence that once one species evolves resistance, it can pass on those resistance genes to other species. They just interbreed, producing hybrids that can then breed with the vulnerable parent species.

In a recent interview, Powles predicted that the Roundup resistance catastophe is just going to get worse, not just in the United States but everywhere where Roundup is used intensively. It’s not a hopeless situation, however. Farmers may be able to slow the spread of resistance by mixing up the kinds of seeds they use, even by fostering vulernable weeds in the way Melander suggested. Resistance is a manageable problem–once you recognize the problem and its evolutionary roots.

Tom Laskawy at Grist:

Grist coverage on the issue of superweeds can be found here, here, here, here and here. Strangely, given that the New York Times Magazine recently did a story about a pair of commodity rice growers who switched over to organic methods for some of these very reasons, the current Times piece omits discussion of any organic or agro-ecological alternatives to chemically intensive agriculture.

For example, the Rodale Institute has for years been growing commodity crops in an organic, no-till style with the same or better yields as conventional and genetically engineered seed. Much of the problem relates to a lack of information on the benefits or techniques required to convert. The “conventional wisdom” among growers is that it’s too costly, in terms of labor and reduced yields, to convert to organic. Kurt and Karen Unkel, the farmers featured in the Times Magazine piece, used a sophisticated custom-built software application to arrive at the financial benefits to conversion.

Rodale itself supplies a conversion calculator right on its website. The costs of new, patented seeds from Monsanto, plus a whole host of new chemicals, plus the additional fuel costs from the need to abandon chemical no-till farming are high — the future of seeds genetically engineered to withstand six different pesticides is a particularly bleak one for eaters as well as farmers. Indeed, the competitive advantage for conventional ag may no longer exist, if it ever did.

Jack Kaskey at Bloomberg:

Dow Chemical Co. plans to add a gene to its corn, cotton and soybean seeds that will allow growers to use a second herbicide to control weeds not killed by Monsanto Co.’s Roundup product.

DHT, or Dow Herbicide Tolerance, will be combined with Roundup tolerance, allowing growers to kill problem weeds with Dow’s 2,4-D herbicide, Antonio Galindez, president of Dow AgroSciences, said today in a webcast of a UBS AG conference presentation. DHT may be available by 2012 in SmartStax corn, by 2013 in soybeans and by 2015 in cotton, he said.

“DHT will bring an unsurpassed solution for weeds that are hard to control,” Galindez said. “We want to see our DHT trait in as many acres as possible.”