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[SANET-MG] Glyphosate resistant weed

Herbicide-Resistant Weed Worries Farmers

December 19, 2006 — By Elliott Minor, Associated Press
TIFTON, Ga. — The cotton industry is concerned about the discovery of a herbicide-resistant weed that spreads easily, can grow an inch a day even during droughts and could force farmers to return to older growing methods that were harsher on the environment.

"It is potentially the worse threat since the boll weevil," said Alan York, weed scientist at North Carolina State University in Raleigh, referring to the voracious beetle that devastated Southern cotton crops in the early 1900s and forced farmers to switch to alternatives such as peanuts.

The boll weevil was eradicated in some states in the late 1970s and early 1980s, paving the way for the return of cotton as one of the nation's major crops, worth $4.7 billion. It is grown in 16 states from coast to coast.

The weed that is causing concern is Palmer amaranth, a type of pig weed that grows 6 to 10 feet tall. Amaranth that resists the most common herbicide used in cotton, glyphostate, has been confirmed in 10 of North Carolina's 100 counties, four of Georgia's 159 counties and is suspected in Tennessee, South Carolina and Arkansas, scientists say.

If someone were trying to design a particularly nasty weed, Palmer amaranth could be the model, York said.

"It's an extremely competitive weed," he said. "It's extremely prolific. It's an efficient ... bad weed."

In Georgia, where the weed has been confirmed in 48 fields, amaranth took over some fields and the cotton had to be cut down, rather than harvested, said University of Georgia weed scientist Stanley Culpepper. The weed can damage cotton pickers, the huge machines that pluck the world's leading natural fiber from the cotton bolls.

Glyphostate is sold under several brand names, but the leading product is Roundup, made by Monsanto.

The company revolutionized cotton growing in the 1990s when it introduced BT cotton -- cotton that was genetically engineered with its own built-in pest defenses. Monsanto also introduced Roundup Ready cotton -- plants that wouldn't perish with the weeds when a field was sprayed with a glyphostate herbicide.

Those two developments enabled cotton growers to drastically reduce the amount of chemicals used in their fields and to switch to conservation tillage, which reduces soil erosion and helps to retain moisture in the soil. The improved efficiency also lowered costs for such things as labor, equipment and fuel.

"That technology I think is the most valuable agronomic tool there is and sustaining it is essential to the viability of the family farm," Culpepper said.

He said Roundup has been "so good, so economical and such a benign herbicide, that we became dependent on it."

It had everything everyone would need," he said. "But when you rely too heavily on one technology, resistance will eventually develop."

Before Roundup Ready cotton, farmers often had to plow the field to bury weeds and their seeds and then protect the crops from pests with heavy chemical applications. Now many use conservation tillage, which barely disturbs the soil.

"If we lost conservation tillage in the Southeast, the financial and environmental consequences would be nothing short of catastrophic," said Eddie Green, who grew 1,750 acres of cotton on a family farm near Unadilla and suspects he may have some of the resistant Palmer amaranth.

He farms in Dooly County, where the resistant weed has been confirmed. It has also been confirmed in nearby Macon, Taylor and Lee counties.

Monsanto, which posted a letter in April alerting growers to the problem, has worked with the Memphis-based National Cotton Council to develop an online course on weed control and is assisting Culpepper, York and others with the resistance problem.

"This is something we do look at very seriously," said Monsanto representative Michelle Starke. "We want growers to be successful with our products."

Monsanto has suggested using Roundup in combination with other herbicides known to kill the resistant weed. Culpepper and others also recommend alternative herbicides.

"We can for sure say it's going to cost more money," said York. "You're going to have more herbicides to try to beat it back. Is it going to put us out of the cotton business? I hope not, but it's going to make it more challenging."

Andy Jordan, the Cotton Council's vice president for technical services, predicted the threat from glyphostate-resistant amaranth will spur farmers to re-examine their weed-management practices.

"The glyphostate-resistant technology in the cotton plant has been a real boon to weed control and efficient cotton production," he said. "If we don't respond ... it could be very serious."

Source: Associated Press

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