SPOKANE — If farmers continue their usual patterns of herbicide use, they'll increase the number of resistant weeds in their fields and burn through the remaining effective chemistries, Northwest researchers warn.
Failure of herbicide systems is one of the most critical problems facing the region's farmers, said Ian Burke, a Washington State University weed science professor.
According to the Weed Science Society of America, once a weed population is exposed to a herbicide to which one or more plants are naturally resistant, the herbicide kills susceptible individuals, but the resistant ones survive and reproduce.
If the same herbicide is repeatedly used, resistant weeds that initially appeared as isolated plants can spread to dominate the field.
Weed control declines each year, WSU weed science professor Drew Lyon said. He pointed to an example in which a herbicide's effectiveness dropped each year, from 100% to 99.98% to 96% to 40%.
"You've been building it all along, you just didn't realize you were building it all along," Lyon said.
Actual timelines vary, depending on a farmer's practices, weed biology and use of herbicides using similar modes of action.
Most farmers believe they can't afford to take the necessary steps to avert herbicide resistance, said Doug Finkelnburg, University of Idaho Extension area educator.
"I would clean my combine before I took it to the next field, but I don't have time for that," he said. "I would tarp my loads, I would make efforts not to spread grassy weeds down the road while I'm moving residues, straws, things like that, but I don't have time. It's going to take me more labor hours, it's going to take more than I'm willing to put in because I've got an operation to run."
The solutions aren't complicated, the industry just needs to figure out how to use them in an economically viable way at the farm level, Finkelnburg said.
Part of the challenge is deciding as a community how to reach "problem neighbors," said Katie Dentzman, UI postdoctoral research associate for agricultural economics and rural sociology.
"What kind of sanctions are there? Is there a certain amount of peer pressure that can be applied, or actual community-based regulation?" she asked.
Idaho farmer Steve Riggers said his biggest concerns are herbicide-resistant Italian ryegrass, wild oats, goatgrass, cheatgrass and downy brome.
"I don't think there's a bigger threat to ag right now," Riggers said. "I'm guardedly optimistic that we can hold the line on this thing but mistakes are going to be costly. ... I think this one issue alone will cause a lot of pressures on a lot of family farms."
Burke, the WSU weed science professor, called for a coordinated Northwest effort to build a sustainable system, similar to the Solutions to Environmental and Economic Problems (STEEP) program, which helped farmers reduce erosion across the region.
STEEP involved economists and sociologists working with growers to solve complicated problems, Burke said. It was one of the programs affected when Congress cut federal earmarks for research in 2011.
The researchers spoke Nov. 15 during the Tri-State Grain Growers Convention in Spokane. They are conducting a series of listening sessions to learn what specific needs farmers have.
"We know what will happen if we keep doing what we're doing," Finkelnburg said. "We've been watching this play out for a few decades now. We need to try something else."