The future is uncertain for dicamba, a herbicide used to kill weeds in soybean and cotton fields that has been controversial since “low volatility” versions were labeled for use in 2017.

The animating issue has been off-target damage, occurring in many of the 34 states where it’s labeled for use. It has prompted lawsuits from environmental groups and farmers and forced EPA and states to impose cutoff dates and other limits on how the herbicide can be used.

In February, a federal district judge in Arizona delivered the latest blow to dicamba, ruling that EPA had not followed notice-and-comment requirements when it approved registrations in 2020. Judge David Bury vacated the registrations, but a few days later, EPA allowed existing stocks of the product still in the supply chain to be used this season.

But next year is in doubt.

Bayer, which makes XtendiMax to go with its dicamba-tolerant Xtend system, and BASF, which manufactures Engenia, have submitted proposed labels to EPA. Syngenta, maker of dicamba product Tavium, has not done so. The company said that it "fully stands behind" the technology of its product for the 2024 growing season but adds, "We will continue to evaluate our options to meet the needs of our customers fin 2025 and beyond."

EPA has classified each application as being for a “new use,” meaning that the agency has 17 months for review and decision under the Pesticide Registration Improvement Act. That would mean decisions on labels would come next fall – too late for use in the 2025 growing season.

EPA has not said whether it plans to take the 17 months, but groups and individual farmers who commented urged EPA to makes its decision in time for next year’s growing season.

“We strongly encourage EPA to continue its work discussing registration conditions with any relevant registrants while reviewing comments to this docket and to finalize a new registration no later than September,” American Soybean Association President Josh Gackle said.

Public comments submitted on Bayer’s proposed label highlight the sharp divisions over continued use of the herbicide.

In general, environmental groups that have urged cancellation of the registrations argued that the proposed language is still too complicated and won’t solve the off-target problems. Label supporters urged EPA to continue to allow use of dicamba, but soybean growers objected to Bayer’s proposal that would not allow post-emergent use. 

Josh-Gackle-ASA.jpgJosh Gackle, American Soybean Association President. The ASA said a decision needs to be made soon, because dicamba-tolerant soybean seeds are being grown now for next year in anticipation that “low-volatility dicamba will be available for use on the tens of millions of crop acres on which there are plans to plant them.” Herbicide manufacturers need enough time to produce new herbicide, with existing supplies “largely exhausted” this season, Gackle said.

Post-emergent use, which would be prohibited under Bayer's plan, is also known as "over the top" application and has been blamed for the drift and volatilization that has caused off-site damage.

“This restriction would significantly limit the agronomical viability of low-volatility dicamba for soybean farmers, especially those who otherwise lack adequate options to control damaging weeds during the vital post-emergent period between when a crop emerges and the canopy closes,” Gackle said.

Registering XtendiMax without allowing post-emergent use “will result in a registration that is not agronomically useful or competitive with other products available to soybean farmers,” he said, meaning farmers may have “to resort to more environmentally impactful weed control methods, including increased soil tillage.”

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ASA also criticized the continuation of an “unnecessarily large” 310-foot downwind buffer to protect endangered species when they are determined to be in the area.

“We are concerned [the buffer requirement] will leave large areas of fields untreated (especially in regions with smaller field sizes), allowing a refuge area for damaging weeds to re-infest fields,” ASA said.

The Center for Biological Diversity, which sued EPA along with the Center for Food Safety in the Arizona case, said the proposed label won’t solve the problems with dicamba.

“Four failed pesticide labels for a single product is indicative of a problem EPA rarely admits: that some labels are just unworkable,” Nathan Donley, environmental health science director at CBD, said in the group's comments.

“Not everything can be mitigated – and that’s ok. It’s not a failing of the agency, just the reality of working with very dangerous chemicals. It’s time to acknowledge that no matter how many times you parse this label out and tweak it here and there, it simply can’t work because it’s unworkable.”

CBD said Bayer’s proposed reduction in application rates for cotton and soybeans are essentially meaningless. The company proposed halving the number of applications, from four to two, and the maximum annual rate of dicamba in both crops from two pounds to one pound per acre.

CBD said the actual amount of dicamba applied in years monitored by the National Agricultural Statistics Service showed that with one exception – cotton in 2019 – growers applied less than the proposed amounts.

“This is important because the massive amount of damage from past registrations occurred despite pesticide users applying far less dicamba than what was allowed on the label,” it said.

CBD also said the label is simply too complicated to follow.

“Every single requirement that was in place in 2020 that made label compliance nearly impossible is still present on the proposed label,” Donley said. “This includes wind-directional buffers, bulletins for ESA counties, addition of volatility- and drift-reduction agents, growth-stage and/or application date cutoffs, use of personal protective equipment, mandatory training, record-keeping requirements, prohibited tank mix partners, wind speed/inversion/rainfall restrictions, and nearby sensitive crop restrictions.”

The Center for Food Safety criticized the agency for not restricting dicamba in cotton, for which Bayer has retained a July 30 cutoff date.

CFS Science Director Bill Freese said, “Dicamba would still be legally sprayed far into summer, ensuring spray and vapor drift damage to crops in the vicinity of dicamba-using cotton growers.”

“Some of the worst dicamba injury to soybeans, other crops, trees and natural areas has occurred in the mid-South region where cotton and soybeans are grown in close proximity, northeastern Arkansas, the Missouri Bootheel and western Tennessee,” Freese said.

Retired weed scientist Ford Baldwin also commented, saying he can’t understand how EPA “can reconcile a proposed preemergence-only label for soybean with a June 12 cut-off while allowing two in-crop applications in cotton with a July 30 cutoff.”

Baldwin added, “This makes absolutely no sense when cotton and soybean are intercropped in the midsouth with the same farmers growing both crops" and would "do nothing to reduce the amount of potential damage in the most heavily affected area in the country.”

Cotton growers and groups that submitted comments said dicamba is essential. Plains Cotton Growers Inc. in Texas supported the proposed label, calling dicamba “a vital tool for managing herbicide-resistant weeds in cotton.”

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