Cotton Journal

December 12, 2008 06:00 PM
Check that breeze blowing outside. If you're in the southeastern U.S., it may be puffing some glyphosate-resistant pigweed pollen your way.

There's plenty of suspicion that the fast-spreading resistant strain of the vigorous weed widens its range through pollen. Research at the University of Georgia's Coastal Plain Experiment Station aims to pinpoint exactly how fast and far glyphosate-resistant pigweed (Palmer amaranth) can move through the air.

Researchers confirmed resistant pigweed in three Georgia counties in 2005. That increased to 10 counties the next year and 20 in 2007.
"It's spreading rapidly through traditional methods like on-farm equipment, but we know movement through pollen is very significant,” says Stanley Culpepper, Georgia Extension weed specialist, who now devotes much of his time to dealing with pigweed.

Just two pigweed plants per 20' of cotton row reduce yield at least 23%, according to Culpepper's work.

"If you have glyphosate-resistant pigweed on dryland cotton, you probably won't pick a crop,” he says. "What could be more devastating to us in cotton?

"We can handle herbicide resistance of just about anything else fairly economically, but not pigweed. There's so much seed production, such rapid growth and it's spread through pollen. All those are connected.”

Lynn Sosnoskie, a postdoctoral student, came to the Tifton, Ga., station to research the resistant pigweed pollen movement. Her work, now under way both in the field and the greenhouse, attempts to track how far and fast the pollen goes. She's pinpointing how much pollen the pigweed plant produces and when it is produced, as well as the length of time the pollen is viable and how the weather affects it.

So far, it looks like the pollen makes tracks in a hurry. In a 75-acre field study with glyphosate-resistant male plants in the center of nonresistant females, pollen carried 300 meters—as far as Sosnoskie was able to measure.

"Palmer amaranth pollen is small, round and fairly smooth. It's designed for wind dispersal. It contains the genetic code of the plant,” she says.

"We're just working out the potential for pollen movement. We want to define the most important mechanism for resistance developing.”

Figuring out how pollen carries resistance will help farmers implement management plans.

"Pollen is important because it could help predict when resistant pigweed will arrive. Farmers need to know the distance it can travel because when it's close, it will change your management practices,” Culpepper says.

"To farmers, this says it's everybody's problem. If it's two farms away or a county away, it's still your problem because of the potential for it to move. Resistance management needs to be practiced by everyone because of the potential to spread,” Sosnoskie says.

"The silver lining to this cloud is that it's going to make scientists, farmers and industry work together more to understand the problems and work through them better, to be more proactive, rather than reactive,” she says. "We're going to think a little ahead. When the next set of herbicide technologies comes along, the question will be how do we preserve them so everybody makes money.”

See you in San Antonio
The Beltwide Cotton Conference heads back to San Antonio on Jan. 5 to 8.

The 2009 conference will run Monday through Thursday. The first day will be devoted to the consultants conference and will include roundtable discussions and interaction from growers, Extension specialists and company representatives.

Tuesday morning kicks off the production conference, with speakers discussing current industry issues. Sessions Tuesday afternoon and Wednesday will focus on specific topics presented by farmers and industry panels. Technical conferences begin Wednesday and continue through Thursday afternoon.

Topics on the schedule include energy management; insect and weed management and resistance; conservation programs; new technology; and cotton economics.

"The workshops are going to be more hands-on and interactive than they've been in the past,” says Bill Robertson, National Cotton Council manager of agronomy, soils and physiology. "We're going to incorporate new electronic techniques for participation that are dynamic.”

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