The U.S. environmental protection agency EPA has opened a public comment period on a proposed regulatory decision to register Dow Agrosciences' herbicide Enlist Duo, a proprietary mixture of 2,4-D choline and glyphosate.

The mixture, intended for use in Dow's Enlist cropping system, requires an EPA review due to the inclusion of choline form of 2,4-D used to control weeds in corn and soybeans genetically engineered (GE) to tolerate 2,4-D.  

Glyphosate is already registered and used widely. However, weeds are becoming increasingly resistant to glyphosate-based herbicides and are posing a problem for farmers.

To ensure that Enlist Duo successfully manages weed resistance problems, EPA said the proposal would impose requirements on the manufacturer, including robust monitoring and reporting, along with grower education and remediation.

The proposal also would allow EPA to take "swift action" to impose additional restrictions on Dow Agrosciences and the use of the pesticide, if resistance develops.

Public comments can be submitted up to May 30, 2014.