In the summer of 2011, Texas AgriLife observers identified the first glyphosate-resistant pigweed in Terry County. At that time, the hope was that the few resistant plants represented nothing more than an aberration, and that removing the weeds would eliminate the problem.
“Each year, it has increased a lot,” says AgriLife research agronomist Wayne Keeling, who has monitored the identification and spread of glyphosate-resistant pigweed from his position at the Texas A&M Research and Extension Center in Lubbock. He recently moderated a panel of industry experts discussing the rise of resistance, the challenge growers face in managing weeds during a period of depressed commodity prices, and the dearth of new herbicide molecules to replace those that no longer work as effectively as they once did.
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“It’s a numbers game,” says AgriLife Extension Integrated Pest Management Specialist Kerry Siders, who works Hockley and Cochran counties. “We seem to be reacting to the problem instead of managing it,” he said during the panel segment of the West Texas Agricultural Chemical Institute’s annual conference in Lubbock.
“This year has been different,” he says. “We’ve had moisture, and it’s been difficult for some producers to make timely postemergence herbicide applications.”
SPREAD HAS BEEN RAPID
Weed control success, he says, depends to some degree on the amount of tillage performed. Proper pre-emergence herbicide incorporation has also paid dividends. “With good incorporation of yellow herbicides, and the addition of residuals in season, producers helped limit the seed bank.”
The spread of herbicide-resistant weeds has been rapid. “It’s bad,” Siders says. “I think we’re well into it, and it can get worse.” He says he’s had calls this summer from dryland farmers who never adopted Roundup Ready technology, but are nonetheless finding herbicide-resistant weeds in their fields.
“Producers still have lessons to be learned,” he says. “We see some holdouts who have not gone back to residual herbicides, but I think in time that will change. Overall, producers are doing a good job re-adopting old herbicides, but in some fields we have to do a better job of distributing yellow herbicides.”
Bob Glodt, research manager, Agri-Search, Inc., an independent agriculture consultant from Plainview, counts himself among the number who thought early resistant weed identification might be nothing more than management issues. It happens.
“We saw a little resistance in 2013,” he recalls. “In 2014, resistance was widespread. The change has been rapid, from one year with a few isolated cases to extreme resistance in just two or three years, to the point Roundup is no longer a useful material for resistant pigweed.”
NEW CONTROL REGIME
He says use of yellow herbicides early and later using hooded sprayers for postemergence herbicide applications when cotton is 12 inches to 14 inches tall should be part of the new weed control regime. “Farmers have to use postemergence materials, especially if they farm more than 500 acres.” Weed control expense poses a serious concern, he says. “At 60-cent cotton, we may see some producers go to alternate crops.”
Peter Dotray, professor and weed scientist at Texas Tech University and Texas A&M AgriLife Research and Extension Center in Lubbock, says, “We first saw resistance in West Texas in 2011. Now, the question is, where isn’t it?. I think it’s all over, and spreading about as quickly as it did in Arkansas. I’ve seen some really ugly fields this year.”
But, like Siders, he says some producers have done an exceptional job controlling weeds under difficult circumstances. While current technology, including residual herbicides, plus some cultivation, add to input costs, it’s probably less than relying on hoe hands to clean up fields.
“Incorporation is the first foundation for resistant weed management,” Dotray says. “Liberty has shown some good results under the right conditions, including proper coverage, proper timing, and the right environmental conditions. It’s important to put all that together. As conditions change, we see less success and less activity from the herbicide.” With stacked technology, he says, producers should think about “making product applications on small weeds.”
Equipment issues have become critical factors in controlling pigweed, says Tim Conley, Wylie Manufacturing, Lubbock. “We’re looking at coverage and drift potential.” Boom height, speed, chemical choice, and environmental conditions are all important, he says.
Incorrect use of spray equipment has been troublesome. “We’ve sped up over the years, and we’ve run booms too high, stirred up dust, and created potential for drift problems. The solution is re-education, putting a program together for each individual based on soil, crop, and product used.”
Education may be even more important with younger farmers, Conley says. “We’re seeing young farmers who have never used a pre-emergence herbicide.” He also noted that producers are pulling old equipment out of sheds and wherever else it was parked when herbicide-tolerant crops came onto the market. “Weed wipers are making a big comeback,” he says.
The numbers matter, Keeling says. “We need to kill as many pigweeds as possible — 99 percent with early treatments, and then get that last 1 percent with residuals and postemergence materials. We also need to look beyond resistant pigweed and consider other problem weeds such as Russian thistle.”
The hope that herbicide-resistant pigweed would be an inconsequential event in West Texas has long disappeared, experts agree. But hope that solutions will emerge from re-adapting old technology, adding new wrinkles with new products and systems, and the dogged persistence that characterizes West Texas farmers, remains intact.