Comment Period on OTT Dicamba Nears End

JEFFERSON CITY, Mo. (DTN) -- Time is running out for the public to share its thoughts on EPA's proposed decision to approve the unconditional registration of three "over-the-top" (OTT) dicamba products for controlling broadleaf weeds in dicamba-tolerant soybeans and cotton.

The federal agency initially opened a 30-day comment period on July 23, then authorized a 15-day extension that ends today, Sept. 6. Comments may be submitted online at https://www.regulations.gov/…

The three OTT dicamba herbicides EPA has proposed for re-registration include BASF's Engenia, Bayer's XtendiMax (referred to as KHNP0090) and Syngenta's Tavium. These products had previously received conditional, five-year registrations in October 2020, but those labels were vacated in February 2024 by a federal court in Arizona that determined the agency had violated the Federal Insecticide, Fungicide and Rodenticide Act (FIFRA) by approving the registrations without providing notice and an opportunity for public comment. While farmers were allowed to use the herbicides under an existing stock order in 2024, the products were unavailable to soybean and cotton farmers during the 2025 growing season.

LABEL LINGO LOWDOWN

Under the previous registration of OTT dicamba products, calendar cutoff dates and crop growth stages were used to restrict the herbicides' application. EPA's current proposal eliminates these means of restriction and instead relies on temperature-dependent requirements that the agency said, "aim to provide flexibility for growers/applicators to only increase mitigations at higher temperature situations when applying dicamba, because the likelihood of volatility of dicamba increases at higher temperatures."

The proposed options for application of OTT dicamba products include:

-- No application of OTT dicamba is allowed when the maximum temperature forecast for both the day of and day after application is equal to or greater than 95 degrees Fahrenheit.

-- Below 75 F, application of a single-use maximum rate of 0.5 pounds acid equivalent of dicamba per acre is allowed with the addition of 20 ounces of a volatility reducing agent (VRA) per acre. Three VRA products, VaporGrip Xtra Agent, Sentris and Suralta, have been evaluated and approved. Others may be approved in the future.

-- From 75 F to less than 85 F, the same maximum rate of dicamba per acre is allowed, but 40 ounces of VRA is required per acre.

-- From 85 F to less than 95 F, the same maximum rate of dicamba with 40 ounces of VRA is required per acre, along with a 40% reduction in treated area. This option would allow growers to return on the third day after the initial application to treat the remaining untreated area following all label restrictions. EPA proposes an alternative to reducing the treated area where applicators may choose to apply dicamba, a drift reducing agent (DRA) and 40 ounces of VRA per acre without any other tank mix partners.

In addition to the application options dictated by maximum air temperature, EPA's proposed registration also includes the following additional mitigations:

-- Every application of OTT dicamba requires the addition of a DRA.

-- A 240-foot downwind buffer must be maintained, and no application is permitted if sensitive crops and/or certain plants are planted on an adjacent downwind field or area. This restriction not only includes non-dicamba-tolerant soybeans but also cucumbers, melons, fruit trees, grapes, peas, beans, peppers, tomatoes and other fruiting vegetables.

-- Application would require that a farmer achieve a minimum of three points of runoff/erosion mitigation as defined by the EPA's Mitigation Menu and consistent with the agency's Herbicide Strategy. More points would be required if the field fell within a Pesticide Use Limitation Area (PULA).

-- No aerial application is allowed. Application must be made with nozzles producing course or courser droplets with a maximum boom height of 24 inches above the target pest or crop canopy. Ground speed can't exceed 15 mph.

-- Application is allowed only when wind speed, measured at boom height, is 3-10 mph. No application is allowed during a temperature inversion.

-- No more than two applications are allowed per year for a maximum annual application of 1 pound acid equivalent of dicamba per acre.

VEXED BY VOLATILITY

According to EPA, the proposed temperature restrictions allow for more flexibility in application timing than crop growth stage and calendar date restrictions implemented for previously registered OTT dicamba products. EPA acknowledges that the labeling requirements it is proposing for volatility mitigation are unique, but the agency wrote such requirements are intended to allow growers to use OTT dicamba products while mitigating potential volatility risks.

DTN spoke to two university weed scientists who aren't so convinced.

"The volatility issues remain unchanged," said Aaron Hager, University of Illinois weed scientist. "We will have volatility and off-target movement if these labels are generated again, just like we've had in the past. We've had off-target movement of dicamba every year for 50 years. Why do we think it's going to change? We have cupped up soybeans in the state of Illinois because of the dicamba that was sprayed not on soybeans, but in corn fields."

Hager questioned what effect the doubling of VRA adjuvant would have on both spray pattern and herbicide efficacy.

"You're putting in twice the amount that we've ever done before. How's that going to work on weed control? I'm not sure anybody's looked at that yet," he said. "I'm not saying these VRAs are completely ineffective, but what I'm saying is that the evidence of off-target movement of dicamba can occur at such a low concentration, it's hard to miss it. If you put enough dicamba across enough acres and enough environments, it will move."

University of Missouri Extension weed scientist Kevin Bradley echoed Hager's concerns. He recalls 2016 and the damage that was caused when dicamba-tolerant crops were available to farmers but the dicamba herbicides formulated for post-emergence application weren't.

"We were being promised that there were these new formulations coming and that there wouldn't be a problem the next year," he said. "I remember going around to winter meetings and telling folks we're going to have these new tools and that what we saw wasn't a prelude of what was to come. But unfortunately, that just didn't come true."

Bradley said that based on 30-year weather data in Missouri, there are less than three days in June when the maximum air temperature reaches 95 F or more. In July, the state averages fewer than seven days at that mark.

"I don't know if 95 is a magical number," he said. "I probably would say it needs to be lower than that because three days out of the month of June -- when a good portion of our herbicide applications are being made -- isn't going to have any major impact. I'd be much more in favor of some of these date cutoffs."

Bradley added that the reason there have been different forms of dicamba on the market is because the herbicide's volatility is well-known. "They have made less-volatile formulations, but I think we ought to be doing everything we can to maximize that dicamba staying where it is applied."

NEXT STEPS

After considering public comments on the proposed registration, its human health risk assessment, benefits and impacts assessment, ecological risk assessment and draft biological evaluation, EPA will decide whether the registration action meets the standard under FIFRA. If the agency determines that the registration action can be granted, EPA will finalize the biological evaluation.â?¯

If a final biological evaluation finds that dicamba may affect any listed species or critical habitats, then EPA will initiate Endangered Species Act consultation and share its findings with the U.S. Fish and Wildlife Service or the National Marine Fisheries Service (collectively referred to as the Services), as appropriate.

During formal consultation, the Services use the information in EPA's final biological evaluation to inform their biological opinions. They are responsible for making the final jeopardy/adverse modification findings and have the sole authority to do so. If the Services determine in their final biological opinions that additional mitigations are necessary to address any jeopardy or adverse modification determination or to address any incidental take, EPA will work with the registrants to ensure that any necessary registration or labeling changes are made.

To read more about the proposed registration of OTT dicamba and to submit a comment, go here: https://www.regulations.gov/…

Jason Jenkins can be reached at jason.jenkins@dtn.com

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