Published 2:10 pm Thursday, August 31, 2023
Field testing is underway for genetically engineered sugar beets resistant to the herbicide dicamba, which biotech critics fear could injure surrounding crops.
KWS, the developer of dicamba-tolerant “Truvera” sugar beet seed, doesn’t anticipate commercialization will be immediate but expects the specifics of sugar beet production would make off-target herbicide damage less likely.
“We’ve got a ways to go before it’s available in the marketplace,” said Mark Schmidt, vice president of sales at KWS.
Representatives of Bayer, the chemical company that co-developed the sugar beet trait and would be responsible for commercializing dicamba specific to sugar beets, did not respond to requests for comment.
The U.S. Environmental Protection Agency hasn’t yet approved herbicide formulations for over-the-top sugar beet spraying, Schmidt said. “None of the registrations have been achieved just yet so we’re talking about a product in development.”
Glyphosate-tolerant sugar beets have long dominated in the industry, but the “triple-stack” Truvera variety can also withstand glufosinate and dicamba, which is intended to stop or delay weed resistance to any one herbicide.
Over-the-top herbicide applications on genetically engineered crops ease weed control for farmers, but repeated and extensive exposure to a chemical can inadvertently select for tolerant weeds — allowing them to reproduce and spread their resistant genes.
“It’s been a very effective tool but resistance to this herbicide can develop in certain populations,” said Schmidt of KWS. “Biological systems have a ways to overcome threats to their existence.”
With a cultivar resistant to three herbicides, weeds that develop tolerance to one chemical could still be killed by the others, discouraging more widespread tolerance.
Growers would be able to rotate through the three herbicides, changing modes of action to prevent that problem from occurring, Schmidt said.
“It just gives you more flexibility,” he said.
Years of problems with “over-the-top” dicamba spraying on other crops demonstrate the hazard posed by the new transgenic trait for sugar beets, according to the Center for Food Safety, a nonprofit critical of U.S. biotech regulations.
“There’s never been this much crop damage from an herbicide in the history of agriculture,” said Bill Freese, the group’s science policy analyst.
Farmers should not be comforted by claims that new types of dicamba have resolved the chemical’s tendency to cause off-target harm, Freese said.
“The vast majority of episodes are due to the supposed low-volatility formulations,” he said.
Biotech critics also claim such seeds only accelerate the “treadmill” of increasing herbicide usage to control weeds, but argue dicamba-tolerant traits are particularly alarming.
Dicamba’s propensity to “volatilize” and drift onto neighboring crops has been blamed for widespread damage in the Midwest, where soybeans tolerant to the herbicide have already been introduced.
These problems prompted the 9th U.S. Circuit Court of Appeals to overturn EPA’s approval of over-the-top dicamba uses for soybeans and cotton in 2020, though the agency re-approved certain applications with additional restrictions later that year.
According to the 9th Circuit, EPA underestimated the risks from over-the-top dicamba use on soybeans.
Complaints about dicamba “skyrocketed” and millions of crop acres were reported damaged in 2017, after over-the-top applications were approved, the ruling said.
An internal EPA audit determined the original approval of over-the-top dicamba was influenced by “senior-level changes to or omissions from scientific documents, including omissions of some conclusions addressing stakeholder risks.”
Despite the additional control measures imposed after the 9th Circuit ruling in 2020, there was “little change in number, severity or geographic extent of dicamba-related incidents,” according to a subsequent EPA report.
If the dicamba-resistant trait is popularized in sugar beets, which are more commonly grown in parts of the West than soybeans or cotton, biotech critics fear vulnerable crops will inadvertently be exposed to the herbicide on a broad scale.
“If I was a potato grower, I would be up in arms about this,” said Freese of the Center for Food Safety.
Tomatoes and green beans are also particularly susceptible to injury from dicamba, as are specialty seeds in Oregon’s Willamette Valley — where sugar beet seed is also commonly produced, he said.
Western droughts associated with climate change are an added cause for concern if the dicamba-resistant sugar beets are commercialized, Freese said.
“Dicamba causes more damage in dry conditions because the crop can’t recover,” he said.
In the Midwest, soybean farmers have often defensively planted dicamba-tolerant crops to avoid harm from the volatilized herbicide, but such protection isn’t available for the West’s diverse specialty crops, Freese said.
“Potatoes don’t have that option,” he said.
Dicamba for over-the-top spraying of sugar beets would be labeled with instructions to minimize volatility problems, said Schmidt of KWS.
No-spray field buffers, proper weather conditions, sprayer nozzle settings and other factors can reduce dicamba’s proclivity to “get up and move, where it doesn’t stay where intended,” he said.
Sugar beets in particular are also conducive to responsible management of over-the-top dicamba, Schmidt said. “There’s a lot more work to do, but that’s some of the promise.”
The timing of sugar beet production is expected to provide farmers with a safer window to spray for two reasons, he said.
“It’s typically the first crop planted, under colder conditions” in which the herbicide is less prone to volatilize, he said. “Other crops that are sensitive to dicamba may not be up.”
Volatilization and drift haven’t caused problems during the past three seasons of field trials, though those plots were under an acre, Schmidt said.
Commercialization of Truvera sugar beets may occur around the “middle of the decade,” meaning between 2024 and 2026, he said.
“There’s still a lot of regulatory work to be done,” he said.
Glyphosate-resistant weeds are generally less common in Oregon and Idaho sugar beet fields, so commercialization would probably arrive later in the West, Schmidt added.
“We think demand will be stronger in other markets first,” he said.
