Researchers are now certain that kochia weeds found growing in two sugarbeet fields in Eastern Oregon and Southwestern Idaho last year were resistant to glyphosate, the active ingredient in the popular weed killer Roundup.
The kochia weed is widespread in the region. Researchers are determining how widespread the resistant weeds are and developing ways to help sugarbeet growers in the region deal with them.
That includes field trials designed to show growers the benefit of using multiple herbicides, in addition to Roundup, to prevent or control the development of glyphosate-resistant weeds.
Virtually all of the 180,000 acres of sugarbeets grown in Eastern Oregon and Idaho are genetically modified by Monsanto Co. to resist glyphosate.
A field trial at Oregon State University’s Ontario research station set up to determine the best treatment method to control resistant kochia weeds is being coordinated by OSU weed scientist Joel Felix and University of Idaho weed scientist Don Morishita.
It was Morishita and Felix who first alerted sugarbeet growers last year they had found kochia weeds that could be resistant to glyphosate. Lab tests have since confirmed that they are.
Both said weeds don’t mutate to develop resistance to a herbicide such as glyphosate. Rather, the product allows a very small population of the weeds that are naturally resistant to thrive because it kills off their competition.
That’s why it’s important for growers to use other herbicides, in addition to Roundup, Felix said.
Roundup might not control a very small number of resistant weeds, he said, but the use of multiple chemistries will. Crop rotation is an important part of that approach because it allows farmers to use different chemistries, he added.
“People who are using (Roundup Ready crops) need to manage that technology by rotating their chemistries,” said Greg Dean, manager of agricultural services for Amalgamated Sugar Co., which purchases the sugarbeets grown by farmers in the region
Some farmers in the area are still relying on glyphosate alone to control weeds, Morishita said.
“Any farmer who is just relying on glyphosate is really setting themselves and their neighbors up for some problems in the future,” he said.
The decision on what herbicides to use is an economic one and it comes down to the grower’s call, Felix said.
But, he added, “We are stressing ... both crop rotation and the use of chemistries other than just glyphosate. As you rotate, you use different modes of action and you control weeds in all crops. By the time you get into sugarbeets, you may be free of kochia if you do a good job.”
Felix and Morishita are collecting weeds from different areas and will spray them with Roundup to try to determine how widespread glyphosate-resistant kochia weeds are in the region.
“It’s really important for ... sugarbeet growers to know if they have glyphosate-resistant weeds on their farm,” Morishita said. “I think we’ll have a better idea of the level of resistance later this year.”
Source: www.capitalpress.com