University of Georgia Extension Weed Scientist Stanley Culpepper has a message for U.S. farmers watching new herbicide technologies move through the regulatory pipeline: be sure to make your voice heard in the process.
“Anytime there’s a tool that’s important to farmers, they need to be commenting and providing input,” Culpepper says, referring to the EPA’s public comment periods during the review of crop protection products.
For farmers fighting herbicide-resistant weeds like Palmer amaranth, waterhemp and kochia, those comments could help determine whether valuable new weed control tools make it across the finish line and to their fields — and whether existing ones stay in the marketplace.
A New Herbicide With a Different Approach
One of the newest technologies moving through the regulatory process now is the FMC Corporation’s herbicide active ingredient, rimisoxafen. The company made its first global regulatory submission of the active ingredient with the EPA earlier this month.
If approved by the agency, rimisoxafen would be the first herbicide to contain two modes of action within a single molecule — a first for agriculture. That would give corn and soybean growers and others a totally new tool to fight some of the most difficult resistant weeds they face.
“It’s that dual mode of action that’s very important from a resistance management standpoint,” says Gail Stratman, Heartland regional technical manager with FMC. “It’s going to be much more difficult for weeds to develop resistance to this, because it’s working on two different parts of the plant at the same time.”
The Weed Science Society of America and Herbicide Resistance Action Committee have classified rimisoxafen as both a Group 12 and Group 32 herbicide because it targets two different sites within susceptible weeds. One mode disrupts carotenoid production, while the other interferes with chlorophyll formation and electron transport, attacking weeds in two ways at once.
That built-in performance will become even more valuable when growers tank mix rimisoxafen with other herbicides.
“When you can mix this with another active ingredient, suddenly you have a product that contains two AIs but is three modes of action,” Stratman explains. “A three-AI product is then four modes of action.”
Designed for Tough Broadleaf Weeds
FMC is developing rimisoxafen as a preemergence herbicide for corn, soybeans, sunflowers and select pulse crops.
Its primary targets include many of the weeds farmers struggle with most — Palmer amaranth, waterhemp, kochia and velvetleaf. The herbicide is also expected to provide suppression of some grass species.
The company recently submitted the active ingredient to EPA for registration after nearly 10 years of research. If the regulatory process stays on schedule, farmers could see the product become commercially available for their use around 2029.
Why New Herbicides Take So Long
Growers often ask why new chemistry isn’t arriving faster to battle weeds. The answer is today’s development process is far more expensive, involved and time-consuming than it once was.
“I used to tell people that 30 years ago it would cost about $80 million and take eight years to bring a product to market,” Stratman says. “Now it costs you $200 million, and it takes 12 to 15 years.”
Those longer timelines also leave companies with less patent life to recover their investment, increasing the importance of every successful product launch.
Stratman says FMC is exploring multiple strategies to maximize its return on investment, with licensing the technology to others as one avenue. Under its agreement with Corteva, the company has access to the active ingredient for use in its own products and premixes, while FMC retains the rights to the active ingredient.
Artificial Intelligence Could Speed Discovery
Anthony “Tony” Klemm, CEO of crop protection company Enko, believes artificial intelligence could help solve part of the discovery timeline and investment challenges.
Rather than testing every potential chemistry in the lab, he says Enko uses AI and DNA-encoded libraries to digitally screen billions of molecules before advancing only the strongest candidates into field trials and regulatory review.
“Traditional pipelines are just not keeping pace with the real challenges, resistance and market demands out there,” Klemm told AgriTalk Host Chip Flory last August. “We combine that use of artificial intelligence with machine learning to better design molecules faster, optimize our leads and reduce our overall cost,” Klemm adds.
While AI can’t shorten EPA’s review process, he says it can dramatically improve the speed and efficiency of discovering safer, more effective herbicides.
Enko currently has about 50 development programs focused on weeds, insects and diseases, including several with entirely new modes of action.
New Tools Won’t Replace Good Weed Management
Even with promising technology on the horizon, researchers caution growers against expecting any single herbicide to solve weed resistance.
Stewardship of existing products remains just as important as developing new ones. Layered residual programs, multiple effective sites of action and diversified weed management practices will determine how long future chemistries stay effective.
“If we lose the tools that we have now, we’re not going to have anything to mix with rimisoxafen,” Stratman says. “Then you put all your pressure on those new AIs and you develop resistance that much faster.”
His advice: protect today’s herbicides so tomorrow’s technologies have effective partners.
“We can’t burn through what we’ve got now hoping that we’re going to have a fix in three years,” Stratman says.
Farmers Have a Stake in The Process
Culpepper encourages growers to do more than wait for new products to reach them. When EPA opens public comment periods on new herbicides or reviews existing products, he says farmers have an opportunity to explain why those tools matter on their operations.
But generic comments aren’t enough.
“You can’t just say, ‘Hey, I need this tool,’” Culpepper says. “You’ve got to [be specific] about the benefits. If you do it right, it can have tremendous influence.”
