What is in this article?:
• Three or four things will occur over the next few years that’ll help farmers in their continuing battle to control resistant pigweed.
UNIVERSITY OF GEORGIA weed scientist Stanley Culpepper describes advances in the battle to control glyphosate-resistant Palmer amaranth pigweed during the recent Sunbelt Ag Expo Field Day held in Moultrie, Ga.
Using large rye
“I think this will be a significant factor to growers in the next three to four years,” says Culpepper. “We’re looking at using very large rye — 6 to 8 feet tall. We roll the rye, and then we plant cotton into it. There are different systems, but what we can do with the rye is to block the sunlight from getting to the ground.
“Pigweed will not emerge without sunlight, so we can basically use a rye cover crop to manipulate the amount of emergence, thereby improving overall weed control. And we can do it with less herbicide inputs to help offset the cost of the rye and the other challenges of that system,” he says.
A final change that will occur for producers in 2015 or 2016 is that they will have cotton that can safely be sprayed over-the-top with 2,4-D, says Culpepper.
“We’ll also have cotton that can be sprayed with dicamba — you may be more familiar with the products Clarity or Banvil, which contain dicamba as an active ingredient. The weed management programs in those technologies will be much more simplistic and much more effective. In fact, as far as the weed management program itself, we’re ready to go today. That’s not so much a concern. The concern is how to manage off-target movement from those plants.”
For example, says Culpepper, very low rate of 2,4-D will damage sensitive cotton. “So if you’re growing 2,4-D-resistant cotton but your neighbor is not, then we have a concern. We have to study and understand off-target movement as we adopt these new technologies.”
Off-target movement usually comes in one of two ways, he explains. “If we spray when the wind is blowing and it moves in the wind, then you’re in trouble.
“The other way is even more challenging, and that’s volatility. You basically spray the herbicide, it sits on the ground, and then an environmental condition helps to lift the herbicide from the soil so that it can move around.
“So volatility has to be addressed. We can’t have a good farmer going out and putting out everything as it needs to be done only to have the herbicide lift and move to sensitive crops.
We’re working on new formulations with all of these products, and we’re testing them to see how likely they are to lift from the soil. In one of our experiments, we put the different formulations of herbicide under a plastic dome with sensitive crops, and we can see which formulations are more volatile than others. That way, when the technology does become available, we can help our growers avoid the negativity of off-target movement.”