By Frank Lessiter of No-Till Farmer USA
Because of serious weed concerns with the area’s over 10 million acres of wheat and barley grown with extremely limited rainfall, Western Australia is the herbicide-resistance capital of the world.
Two of the biggest herbicide resistance concerns for Western Australian notillers are annual ryegrass and wild radish, which have developed resistance to several herbicides over the past 35 years. Studies indicate Western Australian growers are spending an extra 27% per acre to overcome extremely serious weed resistance concerns. And as Iowa State University weed scientist Bob Hartzler points out, U.S. farmers could be facing the same consequences within 5-10 years.
Globally, 255 different weeds have developed resistance to 163 herbicides. Most concerning for no-tillers is that 43 weeds around the world have developed resistance to glyphosate, including 17 species showing Roundup resistance in the U.S. For many years, weed control meant replacing one herbicide with another, what weed scientists refer to as “the treadmill of herbicide resistance.” That thinking is ending now that there’s little in the way of new herbicide chemistry coming soon.
University of Western Australia ag economist David Pannell says a variety of control measures are needed to deal with herbicide resistance, particularly with resilient plants such as ryegrass.
“Ryegrass will develop resistance to any control measure,” he says. “If we just rely on capturing weed seeds as our only measure, ryegrass will evolve to counter that, such as growing flat to the ground so the seeds can’t be captured.”
Pannell says one of the greatest threats is the continued emergence of weeds resistant to glyphosate, which is critical with no-till. Yet he’s convinced Western Australian farmers will find other ways to keep no-tilling if glyphosate is banned. For example, 70% of small grain growers in Western Australia are burning wheat and barley stubble as part of their weed control programs. They’re also looking seriously at mechanical methods, such as pulverizing weed seeds behind the combine. Even if new alternative weed control options are expensive, farmers won’t have much choice but to use them. With sufficient adaption and innovation, notillers can continue to farm profitably despite serious weed resistance concerns.