In that same time period, the company reported that chlorpyrifos was the leading ingredient used to control wheat midge in wheat and that 600,000 pounds were used on roughly 1.6 million wheat acres per year, as well as an average of 105,000 pounds on 350,000 cotton acres per year.

Chlorpyrifos was originally a common household insecticide, as well. Following evidence of health risks, however, the EPA reached an agreement with Dow to phase out most residential uses of chlorpyrifos in 2000, except for ant and roach baits in child-resistant packaging and fire ant mound treatments. The agency also ended chlorpyrifos use on tomatoes and restricted its use on apples and grapes.

In 2015, EPA proposed revoking all food residue tolerances for chlorpyrifos, in response to a petition from the Natural Resources Defense Council and Pesticide Action Network North America, which would effectively end use of the chemical. But that decision was reversed in 2017 by Scott Pruitt, former administrator of the EPA.

Facing litigation and court orders over that move, EPA finalized its decision in July 2019 not to ban the insecticide.

EPA said it would expedite what has been an ongoing review of chlorpyrifos in response to public concerns raised. The agency has until 2022 to complete its review.

The EPA made its decision in July as part of a court order issued on April 19, 2019, by the U.S. Court of Appeals for the Ninth Circuit in San Francisco.

Environmental groups reacted to Corteva's recent announcement with surprise.

"The fact that Corteva is quitting chlorpyrifos as the Trump EPA battles health advocates to keep it on the market is just remarkable," said Lori Ann Burd, director of the Center for Biological Diversity's environmental health program.

The EPA has consistently maintained available science supports the human safety of chlorpyrifos, while environmental groups continue to say it is unsafe for humans.

Some state regulatory agencies have already taken action against the chemical. In July 2018, Hawaii passed legislation to phase out use of chlorpyrifos by 2022. In December 2019, New York governor Andrew Cuomo announced a regulation to phase out use in the state by 2021. And California officials announced last fall that the state would end the use of chlorpyrifos in the state, as a result of an agreement reached with chemical manufacturers.

Under the agreement with Corteva and other companies, all sales of chlorpyrifos products in California were slated to end on Thursday. Growers will no longer be allowed to possess or use chlorpyrifos products in California after Dec. 31, 2020.

Chlorpyrifos use in California has been on the decline since 2005, according to the state's department of pesticides registration. About 2 million pounds of the insecticide was used in 2005, but that fell to about 900,000 pounds in 2016.

DTN Staff Reporter Emily Unglesbee contributed to this report.

Todd Neeley can be reached at todd.neeley@dtn.com

Follow him on Twitter @toddneeleyDTN

(EU/AG)

© Copyright 2020 DTN/The Progressive Farmer. All rights reserved.