On June 30 the U.S. Environmental Protection Agency (EPA) closed a 60-day comment period on its proposed decision to register Enlist Duo herbicide for Dow AgroSciences. It is a proprietary blend of a new 2,4-D choline and glyphosate. EPA received more than 25,000 comments on its proposed decision.
Enlist Duo herbicide is part of the Enlist Weed Control System which includes herbicide-tolerant corn, soybeans and cotton that allow a post-crop emergence application of the herbicide. The company says the herbicide includes the Colex-D Technology package that features near-zero volatility, minimized potential for drift, lower odor, and better handling characteristics than other forms of 2,4-D.
The combination of herbicides is a direct outgrowth of glyphosate-resistant weeds. In a July 1 press release Dow AgroSciences said, “The close of the comment period comes as farmers across the countryside contend with persistent pressure from glyphosate-resistant and hard-to-control weeds. Weeds now dot farm landscapes across the U.S., often out-growing the crops next to them. Resistant and hard-to-control weeds have more than doubled from 2009, and affect an estimated 70 million acres.”
EPA has a responsibility to protect the health and safety of the citizens while allowing farmers to use safe, cost-effective herbicides. Leaning toward one side or the other of that dual mandate will result in the agency not approving a safe, effective herbicide or putting people and the environment at risk. The regulators are partners in operations at the farm level whether they want to be or not and cannot move too far away too quickly from well established farming practice. Not having a regulatory response to glyphosate-resistant weeds is not an option.
The agency has not approved a new mode of action herbicide in the last 30 years. Glyphosate-tolerant crops were released almost 20 years and helped glyphosate dominate the herbicide market and took the economic life out of alternative products that require years of additional research and testing to be ready for commercial use on the farm. Farmers have no choice but to look to older chemicals until the economics of weed control encourage herbicide companies to invest in new technologies.
Dow has used the Colex-D Technology package to address as many of the past problems with 2,4-D as possible. Whether they have done enough is for the regulator to decide. Dow has also decided to mix the two herbicides at a processing plant for ease of use at the farm level. Long-time herbicide users remember the old tank mixes at the local applicator or on the farm and the difficulties of keeping products mixed properly. Dow has tried to make the operation as much like glyphosate alone as possible. That is the standard until conditions force a change.
Dow has been criticized for making biotech seed that is tolerant of glyphosate and 2,4-D. That makes the seed and herbicide combination consistent with current practices and gives them an edge on some competitors that do not produce seed and herbicides. Biotech seeds are not more prone to herbicide resistance than conventional seed. With glyphosate’s low cost and ease of use, overuse and resistance were assured. There are no ‘super’ weeds which grow faster or hardier than other weeds because they are in biotech crops. They became resistant to the most popular herbicide of our time and farmers were slow in responding to it.
EPA said in its “Proposed Registration of Enlist Duo Herbicide” that it has a full and scientifically robust data set on 2,4-D with respect to human health. That data should answer questions about safety for humans and the environment. According to the company, regulatory agencies in more than 70 countries, including the U. K., Germany, France, Canada, Japan, Australia and the U.S., since 2001 have authorized the use of 2,4-D using modern regulatory requirements. Even though it is almost 70 years old, 2,4-D has been judged by modern herbicide standards. Canadian regulators have approved Enlist Duo herbicide and the Enlist corn and soybean traits.
All of this does not mean that Enlist Duo is the savior for current corn, soybean and cotton production practices. A few weeds are already resistant to 2, 4-D; with more use, others could follow unless proper management steps are taken. Dow is recommending a preemergent soil-applied residual herbicide for early season residual control of weeds before the Enlist Duo is applied. This is part of the company’s Enlist Ahead management resource that helps farmers and commercial applicators effectively use the Enlist Weed Control System.
Most policy watchers expect EPA to approve use of Enlist Duo with few changes from its proposed decision. Dow AgroSciences expects to launch Enlist corn and soybeans in 2015. Regardless of what EPA does, that will not be the end of the policy debate. The Texas Department of Agriculture has a request into EPA for an exemption so cotton growers could use propazine this summer to control glyphosate-resistant Palmer amaranth. Propazine is currently approved by EPA for use on grain sorghum in Texas, Oklahoma, New Mexico, Colorado and Kansas. Monsanto has a proposal at EPA for dicamba-tolerant soybeans.
Stewardship programs will become much more important as companies seek to extend the life of products and avoid weed resistance issues. The Enlist Ahead management resource will be central to that effort.