Farmers many times get the bad rap that they’re resistant to change, but that’s not true, especially when their survival depends upon it.

Surveys conducted by the University of Georgia reveal that monumental changes have occurred in a relatively short amount of time as it relates to cotton weed control practices in response to glyphosate-resistant Palmer amaranth pigweed.

During this same time, the cost of weed control in cotton production has roughly doubled.

Based on conservative estimates gathered by UGA researchers, approximately 50 percent of upland cotton in the United States is infested with glyphosate-resistant Palmer amaranth. This resistance developed in response to the widespread planting of glyphosate-resistant cotton varieties.

Early on, as growers were adopting these varieties, surveys were conducted to examine weed control practices. These studies showed that glyphosate use increased — both the number of applications applied and the area to which glyphosate was applied — but there also was  a corresponding decrease in the use of other herbicide classes.

Looking at the widespread nature of glyphosate-resistant weeds — particularly Palmer amaranth pigweed — and the subsequent resistance management strategies, UGA researchers expected there would be another shift in crop production practices.

Understanding these grower practices and how they change, according to the survey, will help fill in the gaps in research and Extension. It also helps to identify potential areas of abuse and prevent additional resistance.

The objective of the study was to determine if cotton weed management in Georgia has changed with glyphosate-resistance Palmer amaranth.

Two surveys were conducted — one was of growers in Georgia about their individual farming practices and the other was of county Extension agents who provided third-party information on a county-wide basis.



Comprehensive survey

A written survey was developed and administered in order to characterize Georgia cotton growers’ production practices before and after the development of glyphosate-resistant Palmer amaranth.

The survey specifically asked growers and Extension agents from across the state to describe the chemical, cultural and mechanical weed control practices that were used on their farms prior to and then following 2005.

Additional questions queried farmers about the costs associated with weed control and about the most significant weeds occurring in cotton.

The surveys looked at the commodities being grown, herbicide use, additional weed management practices, and weed pressure, both before glyphosate-resistant Palmer amaranth — the years 2000 to 2005 — and afterwards, from 2006 through 2010.

Respondents included 65 growers in 16 counties in Georgia and 10 county Extension agents. It encompassed the major row and forage crop areas in the state.

The responding growers were responsible for 13 percent of the state’s cotton, and the total acreage from the county agents responses represented 24 percent of Georgia’s cotton.

Growers produced cotton, peanuts, soybeans and corn, with some livestock, forage and vegetables.

Prior to the development of glyphosate-resistant Palmer amaranth, morningglory was listed as the most troublesome weed pest in row-crop farming.

The growers in the survey said about 78 percent of their acres were infested with glyphosate-resistant pigweed, and the county agents’ number was close to 90 percent of total acreage.

Looking at herbicide use patterns relative to cotton planting and emergence and growth, the survey questioned respondents about the herbicides applied pre-plant and at planting, postemergence over-the-top, and postemergence layby and directed applications.

As expected, with preplant, burndown and at-plant herbicides applied, there was a significant decrease in the acres treated with glyphosate. The use of 2,4-D stayed relatively the same, but there were significant increases in the use of paraquat for controlling Palmer amaranth. The agents saw a significant increase in the use of 2,4-D.

There were significant increases in the amount of diuron, flumioxazin and fomesafen being used, and agents and growers also saw an increase in the amount of pendemetholon being applied in Georgia.

In postemergence treatments, there was a decrease in the amount of glyphosate being applied with respect to the treated acres.



Increase in herbicide use

At the same time, there was a corresponding increase in the amount of glufosinate and metolachlor being used. Similar trends were seen by the county Extension agents who responded.

Growers said post-directed and layby herbicides applied included a decrease in the use of glyphosate while MSMA and diuron stayed about the same.

But there were significant increases in the amount of flumioxazin and metolachlor being used. Agents’ responses were similar, including significant increases in the amount of MSMA and diuron being applied to Georgia cotton acres.

The survey also asked growers how many applications of glyphosate per year were being made. Producers said they were making approximately 2.3 to 2.4 applications of glyphosate per year, both before and after the development of resistant Palmer amaranth.

There was a significant increase in the use of glufosinate for controlling Palmer amaranth. Agents also saw a static number of glyphosate applications but a sizeable increase in the number of glufosinate applications.

Growers are still putting out two applications of glyphosate per year within a crop cycle. However, they might not be placing them on every acre, indicating they may be treating certain fields differently according to the weed pressure.

Looking at costs, growers went from $32 per acre for herbicide weed control to almost $63 per acre. The agents saw an increase of $28 per acre to $68 per acre for herbicide costs.

In 2000 to 2005, 17 percent of growers were hand-weeding 5 percent of Georgia’s cotton acreage at $2 per acre. According to the UGA survey, that has increased to 52 percent of cotton acres being hand-weeded at $24 per acre.

Agents also saw an increase in the amount of acreage being hand-weeded and the associated costs.

The number of acres being subjected to in-row cultivation during the growing season also is increasing.

The survey summarizes that glyphosate-resistant Palmer amaranth is the primary weed problem among Georgia row-crop farmers.

Growers and county agents are reporting similar trends in weed management practices, hand-weeding and cultivation are increasing, glyphosate use — though still high — is decreasing, and at the same time there are increases in the use of other herbicides.

The survey recommends that particular attention be paid to the use of glufosinate, flumioxazin and fomesafen, because of the need to conserve and not over-use, causing more resistance problems.

phollis@farmpress.com


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DYERSBURG, Tenn. — For 15 years, Eddie Anderson, a farmer, has been a strict adherent of no-till agriculture, an environmentally friendly technique that all but eliminates plowing to curb erosion and the harmful runoff of fertilizers and pesticides.



Jason Hamlin, a certified crop adviser and agronomist, looks for weeds resistant to glyphosate in Dyersburg, Tenn.


Related

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But not this year.

On a recent afternoon here, Mr. Anderson watched as tractors crisscrossed a rolling field — plowing and mixing herbicides into the soil to kill weeds where soybeans will soon be planted.

Just as the heavy use of antibiotics contributed to the rise of drug-resistant supergerms, American farmers’ near-ubiquitous use of the weedkiller Roundup has led to the rapid growth of tenacious new superweeds.

To fight them, Mr. Anderson and farmers throughout the East, Midwest and South are being forced to spray fields with more toxic herbicides, pull weeds by hand and return to more labor-intensive methods like regular plowing.

“We’re back to where we were 20 years ago,” said Mr. Anderson, who will plow about one-third of his 3,000 acres of soybean fields this spring, more than he has in years. “We’re trying to find out what works.”

Farm experts say that such efforts could lead to higher food prices, lower crop yields, rising farm costs and more pollution of land and water.

“It is the single largest threat to production agriculture that we have ever seen,” said Andrew Wargo III, the president of the Arkansas Association of Conservation Districts.

The first resistant species to pose a serious threat to agriculture was spotted in a Delaware soybean field in 2000. Since then, the problem has spread, with 10 resistant species in at least 22 states infesting millions of acres, predominantly soybeans, cotton and corn.

The superweeds could temper American agriculture’s enthusiasm for some genetically modified crops. Soybeans, corn and cotton that are engineered to survive spraying with Roundup have become standard in American fields. However, if Roundup doesn’t kill the weeds, farmers have little incentive to spend the extra money for the special seeds.


Supplemental herbicides were applied on Eddie Anderson’s land to combat weeds that are resistant to glyphosate.

Roundup — originally made by Monsanto but now also sold by others under the generic name glyphosate — has been little short of a miracle chemical for farmers. It kills a broad spectrum of weeds, is easy and safe to work with, and breaks down quickly, reducing its environmental impact.

Sales took off in the late 1990s, after Monsanto created its brand of Roundup Ready crops that were genetically modified to tolerate the chemical, allowing farmers to spray their fields to kill the weeds while leaving the crop unharmed. Today, Roundup Ready crops account for about 90 percent of the soybeans and 70 percent of the corn and cotton grown in the United States.

But farmers sprayed so much Roundup that weeds quickly evolved to survive it. “What we’re talking about here is Darwinian evolution in fast-forward,” Mike Owen, a weed scientist at Iowa State University, said.

Now, Roundup-resistant weeds like horseweed and giant ragweed are forcing farmers to go back to more expensive techniques that they had long ago abandoned.

Mr. Anderson, the farmer, is wrestling with a particularly tenacious species of glyphosate-resistant pest called Palmer amaranth, or pigweed, whose resistant form began seriously infesting farms in western Tennessee only last year.

Pigweed can grow three inches a day and reach seven feet or more, choking out crops; it is so sturdy that it can damage harvesting equipment. In an attempt to kill the pest before it becomes that big, Mr. Anderson and his neighbors are plowing their fields and mixing herbicides into the soil.

That threatens to reverse one of the agricultural advances bolstered by the Roundup revolution: minimum-till farming. By combining Roundup and Roundup Ready crops, farmers did not have to plow under the weeds to control them. That reduced erosion, the runoff of chemicals into waterways and the use of fuel for tractors.

If frequent plowing becomes necessary again, “that is certainly a major concern for our environment,” Ken Smith, a weed scientist at the University of Arkansas, said. In addition, some critics of genetically engineered crops say that the use of extra herbicides, including some old ones that are less environmentally tolerable than Roundup, belies the claims made by the biotechnology industry that its crops would be better for the environment.

“The biotech industry is taking us into a more pesticide-dependent agriculture when they’ve always promised, and we need to be going in, the opposite direction,” said Bill Freese, a science policy analyst for the Center for Food Safety in Washington.


Mr. Anderson, who has about 3,000 acres of soybean fields, is dealing with the pest pigweed. 


So far, weed scientists estimate that the total amount of United States farmland afflicted by Roundup-resistant weeds is relatively small — seven million to 10 million acres, according to Ian Heap, director of the International Survey of Herbicide Resistant Weeds, which is financed by the agricultural chemical industry. There are roughly 170 million acres planted with corn, soybeans and cotton, the crops most affected.


Roundup-resistant weeds are also found in several other countries, including Australia, China and Brazil, according to the survey.

Monsanto, which once argued that resistance would not become a major problem, now cautions against exaggerating its impact. “It’s a serious issue, but it’s manageable,” said Rick Cole, who manages weed resistance issues in the United States for the company.

Of course, Monsanto stands to lose a lot of business if farmers use less Roundup and Roundup Ready seeds.

“You’re having to add another product with the Roundup to kill your weeds,” said Steve Doster, a corn and soybean farmer in Barnum, Iowa. “So then why are we buying the Roundup Ready product?”

Monsanto argues that Roundup still controls hundreds of weeds. But the company is concerned enough about the problem that it is taking the extraordinary step of subsidizing cotton farmers’ purchases of competing herbicides to supplement Roundup.

Monsanto and other agricultural biotech companies are also developing genetically engineered crops resistant to other herbicides.

Bayer is already selling cotton and soybeans resistant to glufosinate, another weedkiller. Monsanto’s newest corn is tolerant of both glyphosate and glufosinate, and the company is developing crops resistant to dicamba, an older pesticide. Syngenta is developing soybeans tolerant of its Callisto product. And Dow Chemical is developing corn and soybeans resistant to 2,4-D, a component of Agent Orange, the defoliant used in the Vietnam War.

Still, scientists and farmers say that glyphosate is a once-in-a-century discovery, and steps need to be taken to preserve its effectiveness.

Glyphosate “is as important for reliable global food production as penicillin is for battling disease,” Stephen B. Powles, an Australian weed expert, wrote in a commentary in January in The Proceedings of the National Academy of Sciences.

The National Research Council, which advises the federal government on scientific matters, sounded its own warning last month, saying that the emergence of resistant weeds jeopardized the substantial benefits that genetically engineered crops were providing to farmers and the environment.

Weed scientists are urging farmers to alternate glyphosate with other herbicides. But the price of glyphosate has been falling as competition increases from generic versions, encouraging farmers to keep relying on it.

Something needs to be done, said Louie Perry Jr., a cotton grower whose great-great-grandfather started his farm in Moultrie, Ga., in 1830.

Georgia has been one of the states hit hardest by Roundup-resistant pigweed, and Mr. Perry said the pest could pose as big a threat to cotton farming in the South as the beetle that devastated the industry in the early 20th century.

“If we don’t whip this thing, it’s going to be like the boll weevil did to cotton,” said Mr. Perry, who is also chairman of the Georgia Cotton Commission. “It will take it away.


Ten resistant species of weeds in at least 22 states are infesting millions of acres.


http://www.nytimes.com/2010/05/04/business/energy-environment/04weed.html?pagewanted=1&_r=3

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