EPA Proposes to Re-Approve Combination Herbicide Enlist Duo

A monarch butterfly on a blooming pink flower


Nearly a year after EPA asked a court to withdraw the agency’s registration of Enlist Duo, a new herbicide that combines glyphosate and 2,4 D, the agency now says it wants to maintain the registration and expand it to additional states and for additional crops. After analyzing claims that the combination of herbicides may cause synergistic effects, the EPA now says they do not, and the agency would like to reaffirm its original registration of Enlist Duo. This decision by EPA is frustrating for a number of reasons:   

  1. The EPA should have thoroughly evaluated the issue of whether the combination of herbicides caused synergistic effects BEFORE registering the product for use—not scrambling to look into it long after it was already on the market.
  2. While the agency re-evaluated Enlist Duo, it should have also addressed the many other issues that had already been raised against it in the original court cases, including its failure to address harm to monarch butterflies and its inadequate review of the effects on public health.
  3. In the meantime, the product has remained on the market and in use despite the many (and still outstanding) shortcomings of the agency’s analysis.

In other words, EPA has wasted a year of everyone’s time while Dow was free to sell Enlist Duo, thereby further endangering monarch butterfly populations and posing a risk to human health. We are no closer to resolving the outstanding issues of the effect of this new pesticide combination and now the agency is proposing to expand its use to 34 states. 

Enlist Duo is a potent herbicide made of chemicals that obliterate milkweed, the plant monarch butterflies need to survive. This news comes at the end of another bad year for monarch butterflies. Although the population initially experienced a bump in numbers, a winter storm killed millions of butterflies before they ever even left the Mexican monarch reserve and estimates have remained low as they search along their migration path for the now elusive milkweed host plant that they need to reproduce. 

Additionally, since the EPA first approved Enlist Duo, an international health organization issued findings that glyphosate and 2,4D are probable and possible carcinogens, respectively. This is on top of a number of other significant health concerns related to 2,4 D. 

Furthermore, Enlist Duo is designed to address the issue of weeds that have become resistant to the application of glyphosate alone, and yet its very existence will only exacerbate weed resistance over time while increasing farmer’s dependence on increasingly toxic herbicide combinations.

The EPA has flubbed the approval of Enlist Duo from the very beginning. They are now accepting comments through December 1 on their proposal to expand the registration for Enlist Duo.  Instead, the EPA should do what we asked them to do earlier this year: Cancel the registration of Enlist Duo.