Recently the U.S. Environmental Protection Agency made a rare move to vacate the label for a crop protection product already on the market. Due to concerns regarding “previously unknown” synergies between 2,4-D and glyphosate, the agency vacated the label for Enlist Duo, the new-tech product from Dow AgroSciences. The agency noted more study was needed of the synergistic issues. However, the company has stated it’s confident that the product will be back on the market for the 2016 season.

Recently the company issued a fact sheet on this issue noting that EPA registered the product in October 2014 for use on corn and soybean crops. The registration came after four years of regulatory evaluations, which Dow AgroSciences says represented “an unprecedented level of review, particularly since Enlist duo was a new formulation of two active ingredients that had been widely used – and routinely tank-mixed – by U.S. growers for decades, without regulatory concerns for adverse effects.”

In the final registration decision documents for Enlist Duo, Dow AgroSciences quotes the agency as saying: “The herbicides 2,4-D and glyphosate are two of the most widely used herbicides in the world for controlling weeds. EPA scientists used highly conservative and protective assumptions to evaluate human health and ecological risks for the new uses of 2,4-D in Enlist Duo. The assessments confirm that these uses meet the safety standards for pesticide registration and, as approved, will be protective of the public, agricultural workers, and non-target species, including endangered species.”

The company notes that among the many new requirements for approval of the product was an “unprecedented review of the potential effects of the product on threatened and endangered species.”

In the company’s fact sheet, it reports EPA took on that research in order to help “defend its registration decision from expected litigation brought by pesticide opponents under the U.S. Endangered Species Act. After an exhaustive state-by-state review, EPA concluded that use of Enlist Duo in accordance with the product label would have no effect on threatened and endangered species. The anticipated lawsuit was filed in late 2014 in the U.S. Ninth Circuit Court of Appeals by the Center for Food Safety and Natural Resources Defense Council.

To protect threatened and endangered species in fields adjacent to those treated with Enlist DUO, EPA required a 20-foot wind directional buffer zone, with the size of the buffer being influenced by EPA’s opinion “that there were no synergies of herbicidal action between the 2,4-D choline and glyphosate in the newly registered product,” the company reports.

In fact, the company had filed a claim of synergy between the two active ingredients with the U.S. Patent and Trademark office, which was abandoned by the company when a thorough review of all data “found that synergies were not present in the final formulation selected for Enlist Duo.”

More from the fact sheet

“Dow AgroSciences had not provided this information to EPA, because: 1) the Agency does not typically ask for this type of data; 2) technology providers commonly apply for synergy-related patents without this action posing concerns for regulatory evaluations; and 3) questions of synergies in mixtures on plants had never before been a focus of the Agency’s regulatory decision-making. The data requirements and standards for a patent filing are different from those for a pesticide registration. When EPA learned about this patent application, however, it approached the Ninth Circuit, asking the Court to vacate the Agency’s Enlist Duo registration to give it time to evaluate the issue of synergy outside the context of the activist litigation.

“Dow AgroSciences has now provided EPA with ample data to show that synergy of concern for non-target threatened or endangered plant species does not exist with the final Enlist Duo formulation when used at EPA-prescribed labeled rates of use. Consequently, in the interest of our customers’ pressing needs for Enlist technology to combat resistant weeds, Dow AgroSciences is calling on EPA to support the use of Enlist Duo for the 2016 growing season by promptly: 1) determining that the existing label requires no amendment to ensure protection of threatened and endangered plants; 2) amending the label, if necessary, in time for use in the 2016 growing season; or 3) if the Ninth Circuit Court of Appeals acts to vacate the product’s existing registration, issuing a new Enlist Duo registration, with reasonable use conditions, in time for the 2016 growing season.”

This issue continues to progress through the regulatory system. Dow is confident that it will have that label for the 2016 season.