Little has dampened the enthusiasm for planting cotton in 2011, except for Southeast and Delta growers who are still trying to figure out how to best manage Palmer amaranth — better known as ‘the super weed’.

At a recent meeting of cotton growers in Savannah, Ga., North Carolina State University Weed Scientist Alan York and Monsanto Herbicide Manager Greg Ferguson discussed the ever-increasing problem of Palmer amaranth with a group of Beltwide cotton farmers.

Greg Fikes, who farms in Brooklet, Ga., says he has been fighting resistant pigweed for five years. “We saw our first real resistance with ALS in peanuts. Then, we got pigweed resistance in our cotton,” he says.

“For those cotton farmers in parts of the Cotton Belt who don’t have glyphosate resistant pigweed, don’t think it can’t happen to you. If you don’t take care of the problem the first year, you will be fighting it every year, and it gets worse and worse every year,” the Georgia grower adds.

Kirby Lewis, who farms about 50 miles from Lubbock, Texas says herbicide resistant pigweed, which they call ‘cheatweed’, is increasing in severity in west Texas.

“I’ve been fortunate in that I haven’t had as big a problem with resistant weeds on my farm, but some of my neighbors are having an ongoing fight with them. Some of them used different herbicides, but after the weeds get 3-4 inches tall, there’s not much you can spray on them,” Lewis says.

Hooded sprayers

Ferguson shared some results Monsanto has had in killing large pigweed with a hooded sprayer. He stressed that killing 2-4 foot tall pigweed wasn’t the intended goal, but delays in testing a new hooded sprayer left them with no choice but to try and kill the large weeds.

“We were using two quarts of Gramoxone, a pint and half of Direx and one-fourth percent of surfactant. The surfactant is important — you don’t want to run a crop oil with this mixture — you get a lot better kill using a surfactant,” Ferguson stresses.

“We get better results on larger weeds when we mix urea products, like Diuron or Direx, with Gramoxone. If you get a good rain within a few days of application, you will get uptake of the urea herbicides by the root system, which will enhance control.”

On smaller weeds, Ferguson says, growers can probably do a good job with a lower rate of Gramoxone.

“In our test field, with the large pigweed, if we burned 80 percent of the weed, within four weeks that weed was dead, using the Graxmoxone-Direx-surfactant mix under a sprayer hood. There were some four-foot tall weeds in that field we didn’t kill, but smaller than that we did a good job with the hooded sprayer,” Ferguson says.

Keep spray nozzles clean

Lewis says one thing he’s tried with some success in west Texas is Diuron applied at lay-by. Keeping our spray tips clean when using Diuron has been a problem, he says. We have to stop every morning and clean the screens out.