FMC's new active ingredient targets broadleaf weeds with two modes of action – an industry first. But researchers say good stewardship of existing technologies remains critical.
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.
