Macon County, Ga., has been a hot spot for glyphosate-resistant Palmer amaranth pigweed since it was first discovered in the state. So it’s not surprising that growers there are well-versed in the use of alternative management practices to help control the weed pest.

“Glyphosate-resistant Palmer amaranth was found in Macon County, Ga., in 2005,” says Jeremy Kichler, county Extension coordinator. “I’ve tried to help my growers with this issue over the past five to six years. They’ve used alternative management practices, such as managing the seed bank with deep tillage, cultivating, using wick bars, and hand-weeding.

In Macon County this past year, Kichler estimates that at least 80 percent of the cotton acres were hand-weeded at least once. That’s very expensive and time-consuming, he adds, costing from $20 to $70 per acre, depending on the density of the pigweed.

“A lot of growers become frustrated during planting time when they’re strip-tilling and trying to deal with larger Palmer amaranth with their herbicides. So I’m starting to see acres get out of conservation-tillage and into conventional-tillage,” he says.

Producers are looking at irrigated practices to activate residual herbicides, with residual herbicides being the cornerstone of management practices for resistant Palmer amaranth, says Kichler.

“But we also have dryland situations,” he says. “In Georgia during April and May, we have erratic rainfall patterns that make the activation of these residual herbicides somewhat difficult.

Growers are starting to ask a lot of questions about incorporating residual herbicides, they’re asking about tillage implements, and they’re starting to get out their disk harrowers, which wasn’t so common just a few years ago.”

In trials conducted in 2010, the objective of Kichler and other researchers was to determine the impact of a roto-tiller, a field cultivator and a disk harrow on the activity of Reflex herbicide on Palmer amaranth.

“We had three different scenarios including an irrigated field and two dryland situations, which included a moist soil for the incorporation of our residuals, but not having rain to activate our pre-emergence. Then, we had a bone-dry situation with no soil moisture or rain,” he explains.

In the irrigated site, in Tift County, the trials also looked at crop tolerance to Reflex. The plot size was 6 by 70 feet, replicated three times in a randomized complete block design. Phytogen 375 Widestrike Roundup Ready Flex was planted, and Ignite treatments were made on a timely basis to keep the crop tolerance portion of the trial weed-free.