More weeds developing a resistance to glyphosate (14/7/2003)

More coverage of the weed resistance problems arising from the massive use of Monsanto's herbicide Roundup (active indredient: glyphosate), arising particularly from its use with Monsanto's GM Roundup Ready crops.

"Hartzler suggested Monsanto take another look at its oft-stated assurance to customers that resistance is not an issue."

See also: Weed Could Cost Farmers Millions to Fight, Associated Press

* Weed Resistance May Be Issue with Genetically Modified Soybeans
Weed Resistance May Be Issue with Genetically Modified Soybeans
Steve Tarter
The Journal Star, July 8, 2003

PEORIA, Ill.--An agronomist from Iowa State University has a message for the Monsanto Corp., makers of Roundup Ready seed: Resistance may be an issue.

Actually, the issue is weed resistance in genetically modified organisms like Roundup Ready soybeans, which now makes up 80 percent of the nation's soybean crop.

Farmers who use Roundup Ready beans treat their fields with glyphosate, a chemical that kills weeds by inhibiting a specific enzyme that plants need in order to grow.

Without that enzyme, plants can't produce proteins essential to growth and die. A majority of plants use this same enzyme, so almost all weeds succumb to Roundup.

But not all.

What farmers say makes Roundup Ready soybeans popular is that fields are treated just once with glyphosate -- which doesn't harm the soybeans -- eliminating the cost and time-consuming task of applying a variety of other herbicides.

But herbicide resistance is increasing around the country and that includes resistance to glyphosate, said Bob Hartzler, the extension weed management specialist at Iowa State.

Hartzler suggested Monsanto take another look at its oft- stated assurance to customers that resistance is not an issue.

"If it's a dead weed, it won't produce seed," Monsanto's David Heering told the Farm Industry News, noting the company has worked with glyphosate for 28 years with few resistance concerns.

But Hartzler said more weeds are developing a resistance to glyphosate.

"When glyphosate resistances develops in Iowa, there will be a real cost to those growers who must deal with glyphosate-resistant (weeds)," Hartzler said.

"Almost all weed scientists agree that the evolution of resistant biotypes is inevitable with the current use of glyphosate. We now have ample evidence that nature indeed can duplicate the efforts of Monsanto's scientists and thus it seems a change in philosophy toward resistance management is warranted," he said.

Weed scientist Christy Sprague at the University of Illinois agreed that weed resistance is on the rise. "More weeds are developing resistance because of the use of the same herbicides over and over again," she said.

Farmers need to scout their fields after a herbicide treatment , said Sprague. If they don't, they're likely to see the problem of weed resistance expand, she said.

UNIVERSITY PARK, Pa. -- Field crop producers and landscapers across Pennsylvania should be vigilant over the next few weeks for a new strain of super-weed threatening to gain a foothold in the state, according to an agronomist in Penn State's College of Agricultural Sciences.

William Curran, professor of weed science and extension specialist for Penn State Cooperative Extension, warns that surrounding states have been wrestling with a variety of the common annual weed known as horseweed or marestail. This variety, he says, is showing resistance to glyphosate, the active ingredient in many popular herbicides.

"Horseweed is very common in the Northeast -- it's actually a native species in Pennsylvania," Curran says. "It's mostly a problem along roadsides and areas that aren't tilled. Glyphosate is the active ingredient in Round-Up, TouchDown, Glypho-Max and more; it's the primary product used to kill emerging weeds at planting time. If a weed is resistant to glyphosate, it's a huge threat not only to soybeans but to all crops grown with no-till planting techniques."

In 2000, glyphosate-resistant strains of the weed were identified in a few isolated fields on Maryland's Eastern Shore. By 2001, it had moved into about 30 fields. By 2002, it was in many no-till soybean fields in Delaware. It since has been identified in New Jersey, Maryland, Virginia, Ohio, Tennessee, southern Kentucky and possibly as far west as Missouri.

"This year, we're really concerned about this weed getting a foothold in Pennsylvania," says. Curran "It could become an annual summer problem not just for corn and soybean growers, but also for the landscaping industry, where glyphosate-based herbicides are used frequently to kill weeds among bedding plants, in shrubs and on roadsides."

Over the next several weeks, Curran urges farmers, landscapers and others to keep an eye out for horseweed that isn't controlled by the standard application of herbicide.

"I think it's inevitable that it'll be here -- it probably already is, and just hasn't been identified," Curran says.

"We're talking about horseweed today, but there are other weeds that can develop resistance," he says. "There have been some glyphosate performance problems with common lambsquarters and other weeds on Maryland's Eastern Shore and in portions of the Midwest. There have been more resistance problems worldwide with the ALS-inhibitor family -- a different family of herbicides -- than with any other family, and we're just starting to see those problems in Pennsylvania the last two or three years. The bottom line is that overreliance on any pest management strategy will eventually produce problems and possibly failure. Herbicide or pest resistance is just one example that's close to home."

EDITORS: Contact William Curran at (814) 863-1014 (phone) or [email protected] (e-mail).

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