July 18, 2011


Weeds become more resistant to Monsanto's Roundup herbicide



Weeds are becoming increasingly resistant to Monsanto's Roundup herbicide, sold generically as glyphosate, forcing farmers to use other herbicides that are also losing effectiveness.


Farmers across the US Midwest and South are, increasingly, using herbicide cocktails to combat weeds in cotton, corn and soy fields, according to farmers and weed scientists in Missouri, US.


"It's rather ironic that we were sold glyphosate as an alternative to these older pesticides, and now farmers are using them again," said Brett Lorenzen, a legal analyst with the Environmental Working Group. "But that's part of the pattern of the pesticide industry."


In some areas of Missouri, certain weeds have become resistant to three herbicides, while in Illinois, some weeds have become resistant to four.


Farmers are frustrated that the additional herbicides and strategies are costing them profits, but admit that commodity prices are high enough to justify the additional expenditure.


"It's easily costing US$30 an acre for the hand weeding, and the pre-emergence herbicides are costing US$10 and US$20 an acre," said Tom Jennings, who farms cotton, rice, soy, and corn near Sikeston. "If we see the markets drop back down, the economics are going to get a lot more difficult."


Glyphosate use has risen over the past 15 years, coinciding with unprecedented crop yields and profits for farmers to help propel Monsanto into the world's dominant seed maker.


But reliance on glyphosate, scientists say, has led to an explosion in weeds that are genetically adapting to withstand its application. These weeds adapt faster and more vigorously than their weed cousins, choking fields and clogging irrigation ditches.


"Pollen can transfer the resistant trait," said Kevin Bradley, a weed scientist with the University of Missouri. "There's not much we can do about pollen flying through the air, and that's why we see such rapid spread of resistance."

In recent years, Monsanto has slashed prices, offered rebates to farmers, and given incentives to buy other herbicides, even those of the company's competitors. The company has acknowledged the situation and admitted that it could have more aggressively worked to get the message out about alternative strategies.

Farmers, too, have accepted some of the blame.


"It was so effective and so cheap compared to everything else, that's all you used," Jennings said. "Now we have problems out here and we don't have new herbicides. Before Roundup you had a new product every two or three years. Almost all the new products are just combinations of old products. There's no new chemistry."


Critics of the industry point out that Monsanto and its competitors have known about glyphosate resistance since the mid-1990s, when crops genetically engineered to withstand its application first hit the market. They say the companies should have more clearly warned about over-reliance on glyphosate sooner.


Government-required labels urged farmers to use other herbicides in conjunction with glyphosate, but these suggestions were tucked away in fine print.


"It's hard to read a 54-page booklet," Lorenzen said. "Monsanto has been saying don't just use glyphosate, but farmers don't have time to read the label."


Lorenzen and other industry critics worry that the new herbicide cocktails farmers are using haven't been tested. The Environmental Protection Agency reviews individual herbicides, not combinations. "Nobody tests what happens when all those chemicals are combined together," he said.


Analysts, too, worry that the problem could hit profits.


"They've taken a big hit with [Roundup] already," said Jeff Windau, an analyst with Edward Jones. "So moving forward there could be more pressure on sales."


Windau also said that if farmers start spending too much to combat weeds, the benefits of genetically modified seed could diminish and they will stop buying it.


Monsanto is working on developing soy and cotton that are resistant to the chemical dicamba. The cotton could be on the market within three years.

Video >

Follow Us