WASHINGTON, Dec. 22, 2015 -  Five prominent farm groups are asking EPA to withdraw its request to a federal court to vacate the registration of Enlist Duo, a widely used Dow herbicide.

Last month, EPA asked the San Francisco-based Ninth Circuit federal appeals court to cancel the registration and remand the matter to EPA for further review. The agency said one of its scientists had come across a Dow patent application on the Internet that spoke of Enlist Duo’s potential for “synergistic herbicidal weed control.” This was after EPA had approved Enlist Duo for use and found that the two ingredients mixed together were not more toxic than either compound used by itself.

The active ingredients are 2,4-D and glyphosate, two widely used – and controversial – herbicides.

The letter asking EPA to reconsider its position was signed by the American Farm Bureau Federation, American Soybean Association, National Corn Growers Association, National Cotton Council and National Farmers Union. In their letter, a copy of which was sent to Agriculture Secretary Tom Vilsack, they argue that EPA’s request violates the Federal Insecticide, Fungicide and Rodenticide Act (FIFRA).

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“We are not aware of any other situation where EPA has attempted through a court action to vacate a pesticide registration in place of going through the statutorily-mandated cancellation process,” the said in their letter, dated today. FIFRA, they said, “recognizes due process by requiring EPA to comply with a number of procedural safeguards before a pesticide registration can be cancelled.”

That’s the same argument made by registrant Dow AgroSciences in a brief it filed in the Ninth Circuit on Dec. 7.

“There is no basis in law or logic for this court to vacate the registration,” Dow said. “All that has happened is that EPA has informed this court that it ‘is in receipt of new information regarding potential synergistic effects between’ Enlist Duo’s active ingredients.”

In its filing with the Ninth Circuit, EPA said it “cannot be sure, without a full analysis of the new information, that the current registration does not cause unreasonable effects to the environment, which is a requirement of the registration standard under FIFRA.”

Dow, however, contended, “That is, at most, a reason for the agency to follow the established regulatory process for reviewing that information and taking whatever steps may be appropriate under the comprehensive regulatory regime.”

In a statement issued after EPA’s court filing, Dow said, “EPA has not used observations of potential synergy in mixtures as a basis for regulatory action. Technology providers, like Dow AgroSciences, have commonly filed patent applications on mixtures, without there being any connection to EPA’s regulatory processes.”

Dow said it has voluntarily halted sales of Enlist Duo and is confident that once EPA reviews its data, the product will be available for the 2016 crop season.