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• With well over 100,000 acres of cotton and about a half million acres of soybeans planted this year in Virginia, concern is growing among producers as to the best tools available to manage Palmer amaranth and other herbicide tolerant weeds.
It’s here! If there were any lingering hopes that glyphosate resistant pigweed would stop at the North Carolina line and not be an economic drain on cotton and soybean growers in Virginia — put those hopes to rest.
With well over 100,000 acres of cotton and about a half million acres of soybeans planted this year in Virginia, concern is growing among producers as to the best tools available to manage Palmer amaranth and other herbicide tolerant weeds.
At a recent meeting at the Tidewater Agricultural Research and Extension Center in Suffolk, Va., longtime Virginia Tech Researcher David Holshouser showed farmers the results of high rates of glyphosate applied to Palmer amaranth pigweed from several Virginia counties.
Needless to say, the picture wasn’t a good one for any of the growers in attendance. Some of the Pigweed treated with varying rates of glyposate, up to 56 ounces per acre, showed little or no negative effect from the herbicide.
Holshouser says soybean growers have a few more options than cotton growers in managing pigweed. Regardless of the crop, the key is to use different modes of action to manage these pests and to at least slow down the northward movement of glyphosate resistance problems.
He showed attendees to the recent field day results of a greenhouse study in which high rates of glyphosate were used to kill resistant pigweed. To get a 50 percent reduction in fresh weight in resistant weeds, it took 1-3 pounds of glyphosate, or about 24-56 ounces of Weathermax.
“In cotton or soybeans, you can talk about aphids, thrips, soybean rust, whatever — nothing compares with what growers are facing with resistant pigweeds,” the Virginia researcher says.
Pointing to a picture of a field in Greenville County, Va., Holshouser told grower attendees, “Last year we used a Roundup Ready program in that field, which has a high population of glyphosate resistant pigweed, and the yield was zero — it doesn’t get any worse than that,” he stresses.
Holshouser contends a big reason so many growers shifted to a total glyphosate program was convenience. “The material worked, it was easy to use and relatively inexpensive,” he says.