US EPA revokes registration on Dow’s Enlist Duo

In response to a law suit filed by environmental groups, the U.S. Environmental Protection Agency (EPA) recently revoked the registration of the toxic herbicide "Enlist Duo(glyphosate + 2,4-D) " which contains the cancer causing 2,4-D and is central to future uses of genetically engineered (GE) crops in chemical-intensive agriculture. The marketing of this chemical in genetically engineered agriculture has become integral to the chemical industry's response to weed resistance to the widely used herbicide glyphosate (Roundup), also identified as cancer causing this year by the International Agency for Research on Cancer (IARC).

Approved by the agency just over a year ago, Enlist Duo is a combination of glyphosate and 2,4-D that Dow AgroSciences developed for use on the next generation of GE crops. EPA stated it is taking this action after realizing that the synergistic effects of the combination of these chemicals is likely significantly more harmful than it had initially believed, and that very small buffer zones it had required are not adequate to protect vegetation.

EPA said that it moved to remand the case back to the district court and vacate the registration because 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 (the Federal Insecticide, Fungicide, and Rodenticide Act.)”

EPA had approved use of Enlist Duo in Illinois, Indiana, Iowa, Ohio, South Dakota, Wisconsin, Arkansas, Kansas, Louisiana, Minnesota, Missouri, Mississippi, Nebraska, Oklahoma, and North Dakota, and had intended to approve it in additional areas in the near future.

As part of the registration, EPA required certain drift reduction measures, including a 30-foot downwind in-field buffer from “sensitive areas” in order to avoid effects on non-target organisms, including endangered plant species, located off the field. EPA originally stated that it adequately addressed the issue of synergism between glyphosate and 2,4-D in the product, but it recently discovered that Dow made claims of “synergistic herbicidal weed control” in its provisional and non-provisional patent applications for Enlist Duo. On Oct. 13, it sent Dow a letter regarding the information in those applications, and Dow responded on Nov. 9. “An initial review (of the information in the Dow response) indicates that the 30-foot buffer included in the registration may not be adequate,” EPA said in the court filing.