The superweeds are coming!


The enemy grows among us, and it's spreading. Worse, its powers stand to increase.

Invading legions of superweeds have taken root in our fields. In California, growers battle at least 24 different types of herbicide resistant weeds, in nearly 2,000 sites across more than 200,000 acres. Idaho weed scientists report infestations across 240,000 acres. Around the U.S. the number of acres infested with weeds resistant to a single herbicide, glyphosate, totals 14 million. These plants, which once withered away with an application of glyphosate, known commercially as Roundup, now laugh in the chemical's face and sprout bravely on.

Such brazen pluckiness is becoming a major problem for farmers. Many growers routinely rely on Roundup to clear their fields for planting. Many others plant Monsanto's "Roundup Ready" crops, plants that have been genetically engineered to withstand the herbicide. This allows them to spray during the growing season, clearing out weeds growing amongst the crops. It is a convenient system, and since 1996, the year Roundup Ready soybeans became commercially available, glyphosate use has risen sharply. Today, the majority of crops grown in the U.S. are Roundup Ready.

But this trait of herbicide resistance, birthed through years of painstaking work into soybeans, corn, cotton, canola, alfalfa and sugar beet crops by Monsanto's scientists, weeds have achieved naturally. The constant application has unintentionally selected for and breed resistant weeds. It's elementary evolutionary biology: Apply a selection pressure and watch an organism evolve in response. And while this, allegedly, was a surprise to Monsanto scientists, the plants are only behaving exactly as we'd expect them to. (And as several scientists predicted they would. [PDF])

"What I'm really concerned about," said Don Morishita, a research scientist and extension adviser at Twin Falls Research and Extension Center in Idaho, "would be any situations where farmers are growing Roundup Ready crops in rotation, such as sugar beets, corn or alfalfa. This isn't the typical crop rotation around here, but it's something I'm really trying to caution farmers against."

There are no confirmed glyphosate resistant weeds in Idaho yet, Morishita says, (confirmation is a lengthy and involved process) but weed scientists suspect them in the western part of the state. "Farmers are reporting weeds that are difficult to kill with Roundup," he says. "It takes a couple of generations to reach full resistance. So this problem is literally knocking on the doors of Idaho."

To fix the problem, Monsanto and Dow are developing new crops with "stacked" herbicide resistance. Monsanto is pairing glyphosate and dicamba resistance, Dow glyphosate and 2,4-D. Using these crops, farmers would spray several weed killers at a time, instead of one, in the same way doctors treat resistant infections with multiple antibiotics.

Beyond more Roundup, this would mean far heavier applications of 2,4-D and dicamba, an older pesticide known commercially as Banvel, Oracle and Vanquish. Both chemicals are more volatile than glyphosate, and more prone to drift. While the US Environmental Protection Agency has classified both herbicides as being relatively benign to mammals, birds and fish, they're highly toxic to other plants. One farmer's crops could be damaged by another's application of herbicide.

Nor, from a human perspective, are the chemicals worry-free. Dioxin, for example, is a contaminant produced in the 2,4-D manufacturing process. Even at low levels, dioxin is a potent neurotoxin. Out of these concerns, the Natural Resources Defense Council filed a lawsuit against the EPA in February for their failure to respond to a petition to ban the chemical.

And of course, stacked resistance is not a true solution, merely a delay of the problem. The application of multiple herbicides would promote multiple herbicide resistant weeds, in the same way that the abundance use of multiple antibiotics has lead to multiple antibiotic resistant bacteria. The medical field has reacted to this problem by escalating the number of antibiotics they use to treat infections. Seed/chemical companies are poised to do the same.

"You have a patents from DuPont where they envision having as many as seven or more herbicides [stacked in resistance], " says Bill Freese, a science policy analyst at the Center for Food Safety (see paragraph 33). "Monsanto has plans for triple resistant crops."

This, laments Freese, would lead to an ever-increasing dependence upon companies who supply seeds and the chemicals to use those seeds. "It shouldnt surprise us," he says. "It makes great business sense, it’s just a really bad idea from almost every other perspective."

There has been considerable outcry over this and related developments. Academics have protested stacked resistance in peer-reviewed literature and penned joint letters to the EPA (PDF), over pesticide-resistant insects evolved in fields of GM corn.

We're at a critical juncture, says Dave Mortensen, an agro-ecologist at Penn State. "Now is the time to decide whether we'll repeat past mistakes."

The stacked-resistant seeds have been developed and ready for market for a while now, but the Environmental Protection Agency and the Animal and Plant Health Inspection Service, the two agencies that review genetically modified crops, are just starting their first reviews.

There are other paths for farmers, Mortensen says. Focused crop rotations, cover crops, mulches and reducing the number of annual sprays would all be better options than embracing stacked resistance.

We could, of course, simply keep throwing our heavy artillery at weeds. But, given the ingenuity of plants, they're liable to incorporate the metal casing into their armor, to deflect all our military might. We know how plants behave. How we will behave remains to be seen.

Danielle Venton is an intern at High Country News.

Images: 1) "Scouting for Glyphosate Resistance," from the North Dakota State University and University of Minnesota Extension, via YouTube; 2) The beasts of the field come in all forms, image from Friends of the Prairie Learning Center at the Neal Smith National Wildlife Refuge/Flickr.

High Country News Classifieds