Excerpt from article in the New York Times by Andrew Pollack:
The Environmental Protection Agency, in a surprising move, has decided to revoke the approval of a herbicide that was made to be used on a new generation of
The agency’s decision could delay the introduction of corn, soybeans and cotton developed by Dow Chemical to be resistant to the herbicide 2,4-D. But Dow said it did not anticipate a significant delay.
In a court filing on November 26, the E.P.A. said it had discovered new information suggesting that the herbicide, which Dow calls Enlist Duo, could be more toxic than previously believed.
“E.P.A. can no longer be confident that Enlist Duo will not cause risks of concern to nontarget organisms, including those listed as endangered, when used according to the approved label,” the agency said in its filing to the United States Court of Appeals for the Ninth Circuit in San Francisco.
Dow said in a statement that the concerns of the E.P.A. could be resolved in time for the 2016 growing season.
“We continue to prepare for commercial sales of Enlist Duo for the 2016 growing season with enthusiastic grower adoption,” said Tim Hassinger, the president of Dow AgroSciences, the company’s agricultural division.
The E.P.A. had approved Enlist Duo in October 2014 for use in six of the top corn-producing states, and in March of this year for use in nine more states. The crops themselves have been approved by the Agriculture Department.
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Here is the EPA’s motion filed in the Ninth Circuit.
Weed scientist Andrew Pollack has an analysis of the “synergistic effects” concern on his blog. Here are some excerpts:
I’m not going to wade too far into the policy (or politics) behind this decision. … But I do think this is a good opportunity to explain what “synergistic effects” are with respect to herbicides.
Synergism, as you might guess, means that the two herbicides work better when applied together than we would expect based on how effective they are when applied alone.
…
If two herbicides are synergistic, we can get better weed control, sometimes even at reduced herbicide rates. I’ve published two studies where we found synergistic interactions between herbicides, and in both cases it was very helpful for controlling weeds (Study 1; Study 2). However, herbicide synergism can be problematic if we don’t know about the synergistic interaction ahead of time. If the synergism isn’t known, it is possible that the herbicide mixture could cause injury to crops or other non-target plants. And this seems to be the reasoning behind EPA’s decision to withdraw the Enlist Duo registration.
