The New Rules of Products Containing Dicamba Herbicide

Legislators and regulators, supporting scientifically sound policy, will keep these valuable products available to growers — with a few changes.
The New Rules of Products Containing Dicamba Herbicide
Dicamba helps keep rows clean and soybean plants flourishing — like these young plants in a Minnesota soybean field.
Registration of over-the-top dicamba products recently spurred yearslong national debate and prompted more states to higher levels of involvement in pesticide label requirements. The result is a trend toward increased state and national conversation prior to registration of more complex regulatory approvals and increased opportunity for state-specific pesticide guidelines to recognize local needs.

With states becoming generally more involved and more actively engaged in product registrations, their perspective now will be included earlier in the process. However, this additional step could potentially slow down what is already a long, arduous process for bringing new technologies to market, says John Abbott, head of regulatory & stewardship for Syngenta, North America.

States have expressed an interest in having greater and earlier input on dicamba herbicide. The U.S. Environmental Protection Agency’s (EPA’s) Federal Insecticide, Fungicide and Rodenticide Act section 24(c) has also given the states the ability to request local label changes for pesticide use.

Products like Tavium provide growers with valuable tools to control weeds that threaten farm profitability as well as the long-term sustainability of their operations.

Pete Eure
Technical Product Lead

While the EPA used to allow states to move cutoff deadlines either up or back through a 24(c), recent decisions have indicated that states should follow another process for more-restrictive uses, and the allowance for less-restrictive labels is currently under review.

“The process for providing special local needs for dicamba products appears to be changing,” says Carroll Moseley, Ph.D., head of state regulatory affairs for Syngenta, North America. For instance, he says, some cotton-growing states recently sought an extension of the application window in soybeans so the window of application in cotton and soybeans would close on the same day. The EPA turned down those recent dicamba 24(c) requests. “In the past,” Moseley notes, “24(c)s were used, in some states, to make application windows more restrictive.”

More Rules With Recent Registrations

In 2020, the EPA reissued registrations for two over-the-top dicamba products and extended the registration for Tavium® Plus VaporGrip® Technology herbicide, the Syngenta dicamba premix. These registrations are only for use on dicamba-tolerant cotton and soybeans and are scheduled to expire in 2025.

Tavium, which can be used preplant, at planting and early post-emergence, provides a combination of the contact control of dicamba and the residual control of S-metolachlor. The herbicide is designed to manage key ALS-, PPO- and glyphosate-resistant grass and broadleaf weeds.

The 2020 registrations included some changes for users of the products to help mitigate the potential risk of herbicides drifting from the application site onto neighboring crops. On the previous label, the downwind buffer was 110 feet; it is now 240 feet. The downwind buffer if endangered species are present used to be 110 feet — now it’s 310 feet. An omnidirectional buffer of 57 feet remains as is.

Other changes include national cutoff dates for its use on soybeans — June 30 — and on cotton — July 30. Stanley Culpepper, Ph.D., extension weed specialist at the University of Georgia, disagrees with those cutoff dates. “The theory that a one-size-fits-all application cutoff date will improve on-target pesticide applications is simply not supported by extension surveys or data generated in Georgia,” he says. “What this date will likely do is reduce a farmer’s ability to use the tool effectively in a sound weed management program.”

Additionally, all over-the-top soybean and cotton herbicide applications now must include a buffering agent. “It just means that we must continue to be vigilant about how we apply this product and make sure that we apply it properly,” Moseley says.

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Because training is mandatory for those who apply dicamba products, Syngenta offers qualified webinars and an online dicamba applicator training module.

All trainings include the latest state-specific guidelines, says Pete Eure, technical product lead for Syngenta. “Some states have additional guidelines, including application date changes that may be different from the federal label. We have these state-specific guidelines in our live webinars as well as our online training modules.”

Valuable Tool for Resistance

Cost-effective options to control herbicide-resistant weeds affecting soybean and cotton crops are limited, making dicamba an important tool. In recent years, the adoption of dicamba increased dramatically. In 2018, approximately 41% of U.S. soybean acreage was planted with dicamba-tolerant (DT) seed. In cotton, DT seed commanded almost 70% of the U.S. acreage.

Jay Behn, a grower and retailer in Hampton, Iowa, relies on dicamba. “Tavium Plus VaporGrip Technology herbicide pretty much controls everything,” he says. “The stuff we've used in the past burnt the tops off the weeds and allowed them to come back two weeks later.” With Tavium, he doesn’t have that problem.

Eure knows dicamba is highly valuable to growers. “Palmer amaranth and waterhemp have developed resistance to other herbicides; and when these are left uncontrolled, they can cause yield loss and produce seed that will germinate and compete with next year's crop,” he says. “It’s important that we control those weeds with tools like dicamba.”

What will continue to show the way forward for weed management and product registrations is a science-based approach — and Syngenta supports that.

“Products like Tavium provide growers with valuable tools to control weeds that threaten farm profitability as well as the long-term sustainability of their operations,” Eure says. “We want to continue to offer tools using that science-based approach so that we ensure future farm generations have clean, productive fields.”