Misuse of gene-altered crops can cause problem

by Rachel Melcer


Two Missouri farmers are providing Monsanto Co. and a University of Missouri scientist with a cautionary tale: Misuse Monsanto's Roundup Ready weed-control system, and you're likely to create a stronger weed.

On two separate soybean fields in the northwest part of the state, scientists have found common waterhemp, also known as pigweed, that shows signs of resisting glyphosate herbicide. Creve Coeur-based Monsanto sells glyphosate as Roundup.

It is one of the most effective, relatively safe and commonly used agricultural weedkillers.

It also is the cornerstone of Monsanto's blockbuster Roundup Ready crop technology. The company has genetically modified soybeans, corn, cotton and canola to withstand glyphosate. The result: Growers can spray Roundup over the top of their fields to kill weeds without harming the crop. <http://oas-central.realmedia.com/RealMedia/ads/click_lx.ads/www.stltoday.com/news/sciencemedicine/295477530/Frame1/default/empty.gif/33663966373431353432363463666430?>

But if the same crop and herbicide are used on a field, year after year, weeds with a natural genetic resistance to glyphosate will survive - and thrive. Then each year, the number of resistant weeds can multiply until they choke the crop and reduce yield.

That is what happened on the northeast Missouri fields, said Kevin Bradley, extension weed scientist and assistant professor at the University of Missouri at Columbia. He would not identify the fields or farmers, but said the farmers had irresponsibly planted Roundup Ready soybeans every year since the seeds became available in 1996.

Waterhemp taken from their fields last year withstood eight times the recommended dose of Roundup. If field studies planned for next summer show that the ability is inherited by new generations of waterhemp - something that Bradley considers "highly likely" - then it will be classified as Roundup resistant.

Universities and agriculture companies try to teach growers to vary crops and weedkillers each year, Bradley said. "But it's their bottom line. We can tell them to rotate to this other herbicide, but (that) costs $2 or $3 more per acre. And it doesn't make financial sense to some of them. ... You just can't compete with the Roundup Ready system.

"Sometimes it's that attitude - 'It's not a problem until it's a problem on my property, and I'll deal with it when I get it.' And that's what we have here," he said.

Monsanto said 101.5 million acres in the United States were planted with Roundup Ready crops this year. The company globally sold nearly $1.6 billion in Roundup and other glyphosate products in the nine months that ended May 31.

And Roundup Ready traits account for the bulk of the $2.7 billion in seeds and traits Monsanto sold in the same period.

These sales could be threatened if the number of glyphosate-resistant weeds continues to multiply. Eight species globally - five in the United States - have been classified since 1996, according to a consortium of weed scientists.

Less than 1 percent of all planted crop acres in the United States have had problems with glyphosate resistant weeds, said Harvey Glick, director of scientific affairs for Monsanto. And the herbicide is designed to kill more than 100 species, so the percentage of those it does not affect is small. Still, "we take all of those cases very seriously," he said.

On Oct. 3, Monsanto debuted a Web site offering information to growers on how to avoid weed resistance and how to deal with it if it occurs. Last month, Monsanto competitor Syngenta AG did the same.

Yet some critics say the companies are doing too little, too late.

Margaret Mellon, director of the food and environment program for the nonprofit Union of Concerned Scientists, said Monsanto should have contractually required farmers using its Roundup Ready crops to rotate them each year.

"This is an absolutely predictable problem," she said. "I don't think anybody is surprised now that it is upon us."

The companies' stepped-up education effort "is an acknowledgment that it's a problem (and) that it's their problem," Mellon said. "I think they have a responsibility to be there, right up at the front of the response effort."

Monsanto is working with Bradley on Missouri's hardy waterhemp, just as it volunteers assistance to any extension scientist dealing with potentially resistant weeds. The typical result is advice for the growers on herbicides and mechanical methods that can be used alongside glyphosate to kill the resistant weeds.

These pests can be controlled, Bradley said. But there are challenges. If a resistant weed has seeds that become airborne, it can easily spread to neighboring fields. What's more, the number of agricultural pesticides available is limited, so it can be tough to find one that works well on a particular type of weed.

Waterhemp poses the latter problem. It "is one of those scary ones, in that we don't have a lot of (other) options for dealing with it," Bradley said.

Dealing with resistant weeds also diminishes key benefits of Roundup Ready crops: cost savings and reduced use of pesticides.

"It's not a bulletproof system. That's what we're learning," Bradley said. He estimates the two Missouri farmers will have to spend at least an additional $4 to $5 an acre to kill their waterhemp.

Still, no one believes that Roundup Ready crops will go away. They are too widespread, and the benefits outweigh costs, even when treating resistant weeds.

But more careful stewardship will be required, Mellon said. Glyphosate is valuable for many nonfarm uses - clearing foliage along roadways or around public facilities and maintenance around homes, for example. Growers and manufacturers should begin to guard it as a public trust, she said.

Bradley said he and other extension scientists will use the waterhemp example to wake up growers in states such as Missouri, Illinois and Iowa, where it had been a major pest before the Roundup Ready system.

"Maybe we can use this for good," he said. "What we're looking for, hopefully, is to use it as a tool to educate farmers about what can happen."

Bradley hesitated to blame growers entirely, saying that Monsanto has made Roundup Ready crops too good to resist, tempting farmers to plant them year after year. But farmers need to avoid being short-sighted, he said.

Monsanto's Glick said: "At the end of the day, the grower is going to make the decision that he thinks is best for his particular operation. And all we can do is provide him with the information to make the best decision."

*Roundup Ready Web sites*

Agricultural companies are stepping up efforts to educate farmers about the proper use of Roundup Ready crops, which are genetically modified to resist glyphosate herbicide. If the crops are irresponsibly planted, weeds that also are resistant can appear, reducing the value of the system.

Two firms recently unveiled educational Web sites:
*Monsanto Co., http://www.weedresistancemanagement.com
*Syngenta AG, http://www.resistancefighter.com

*rmelcer@post-dispatch.com 314-340-8394


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Oktober 2005

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