What is in this article?:
- Atrazine, pigweed issues on the minds of corn growers
- Protect the technology
• Atrazine is under the microscope again.
• Concerns also have arisen about atrazine resistance.
• In recent years, some growers have asked for recommendations on controlling Roundup Ready corn in a replant situation.
Protect the technology
With LibertyLink cotton, corn and soybeans all now available, growers need to be careful and protect the technology, he says.
Resistant Palmer amaranth pigweed is pretty much spreading throughout the Southeast region, says Prostko. As for control strategies, growers should first start with a clean field, he says.
“We’re lucky in Georgia that 65 percent of our corn crop is irrigated, and we can use irrigation to activate residual herbicides. Also, if you haven’t been tilling in awhile, you’ll certainly see the benefit of a moldboard plow, maybe not every year, but once every three to four years. Using extreme cover crops, residual herbicides and timely postemergence applications are other keys to controlling resistant pigweed, he says.
Herbicide programs are available, says Prostko, for controlling Palmer amaranth in field corn.
“As far as residuals, we still rely on atrazine. We can use Dual Magnum in areas where atrazine resistance might be a problem, and we can use Micro-Tech. In Roundup Ready corn, we’ve seen success with glyphosate, atrazine and Prowl; Expert, which is a three-way mix of atrazine, glyphosate and Dual; and Halex GT, which is a three-way mix of glyphosate, Dual and Callisto.
“For LibertyLink corn, Ignite and atrazine is our foundation. Whether or not we mix in Prowl depends on if we’re having problems with Texas millet. For conventional growers, some programs that have looked good have included Steadfast Q and atrazine and new products like Laudis and Callista.”
Also, it’s important to manage post-harvest populations of Palmer amaranth, he says. “We get our corn off in late July, early August, and don’t get a frost until mid-November. So that’s a long time frame when we let these populations produce seed. In the fall, they can go from seed to seed in 35 days. You might have done a great job in corn all year, but if you allow these populations to go to seed, we’re back to ground zero.
“We can mow or till, and we can use something like paraquat and 2,4-D. There are a lot of control strategies, with the goal being to prevent those plants from producing seed.”
With resistance becoming more of an issue, Prostko says growers might want to consider some of the products that have been introduced in recent years. These can include products like Callisto, Laudis and Status. Callisto is a postemergence herbicide with a unique “bleaching” mode of action. Laudis is another product with a “bleacher” mode of action, while Status contains dicamba and is used for broadleaf weed control.
Looking to the future, Prostko says Dow Agroscience will be releasing DHT corn with enhanced tolerance to 2,4-D and products like Assure or Fusilade. It’ll also be stacked with glyphosate. “New herbicides include Zidua, which probably will come out next year. It’s a grass herbicide. The other one is Capreno, which is labeled right now.”