Dow Weed Killer Re-Approved After Patent Raises Questions

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By David Schultz

Nov. 1 — The Environmental Protection Agency once again gave its stamp of approval to a new weed-killing pesticide from Dow Chemical Co. following a review a court granted in response to an agency request.

The EPA’s move allows Dow to continue selling its Enlist Duo pesticide, which is designed to be used alongside Dow’s Enlist line of genetically modified seeds. Dow said in a 2014 annual report that it expects its Enlist line of products to generate $1 billion in revenue between 2014-2018, primarily on corn and soybeans.

Last year, the EPA took the unusual step of asking a federal court to give it another opportunity to review its initial approval of Enlist Duo. The agency told the court it had reviewed the application Dow had submitted to the U.S. Patent and Trademark Office to patent Enlist Duo and discovered a discrepancy.

In the patent filing, the company had claimed the weed killer’s mixture of two chemicals, 2,4-D and glyphosate, amplified each other’s effects and created a pesticide more potent than the sum of its parts, according to EPA spokesman Nick Conger. However, Dow had not made these claims to the EPA during its review of the product’s health and environmental risks, Conger told Bloomberg BNA.

Dow’s stock price dipped by more than two percent the day the EPA’s request to the court was first reported by Bloomberg BNA.

All Clear

Now, after a 10-month review, the EPA concluded that the data on Enlist Duo “confirms EPA’s initial findings” that the chemicals do not amplify each other, according to an agency statement released Nov. 1.

The EPA’s finding essentially preserves the status quo for Dow. The court that was hearing a lawsuit over Enlist Duo brought by several environmental groups chose to keep the EPA’s 2014 approval of the weed killer intact, which meant Dow could continue to sell it to farmers during the agency’s now-concluded review.

But the findings also raise the question of whether the claims Dow made in its patent application were false. Rachelle Schikorra, a Dow spokeswoman, told Bloomberg BNA that they were not.

She said the U.S. Patent and Trademark Office has “a different standard of data requirements” than the EPA does and that the company’s claims that the two chemicals amplified each other were “based on a limited dataset.” When looking at the entirety of the data on Enlist Duo, it’s clear there is no amplification, Schikorra said in an e-mail.

In addition to completing its re-review of Enlist Duo, the EPA also announced a proposal to expand where it can be used and on which crops. Currently, it’s used to suppress weeds on corn and soybean crops. The EPA is weighing whether to allow farmers to use the pesticide on cotton.

To contact the reporter on this story: David Schultz in Washington at

To contact the editor responsible for this story: Larry Pearl at

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