The denial prevents 12 growers from applying the only effective means of removing a pest that plows up shellfish beds and causes oysters to sink and suffocate.
The growers charged Ecology with being driven by public hostility to spraying, rather than science. Ecology maintained it was guided by the potential harm to other creatures.
“We based our decision off the scientific data we have,” Ecology spokeswoman Jessica Payne said. “This pesticide was too risky to be used.”
Ecology’s stance reverses a decision it made in 2015 to let growers spray imidacloprid, a neonicotinoid pesticide widely used on land crops. Ecology initially defended the spraying as ecologically sound. However, consumer, activist and media disapproval pressured growers and Ecology into backing off.
Growers scaled back plans, proposing to spray 500 acres instead of 2,000 acres, and reapplied for a permit in 2016. Ecology reported receiving more than 8,000 comments on the application. On Monday, it announced that it was denying the permit and cited new research for its change of view.
Washington State University scientist Kim Patten, who has researched eradicating burrowing shrimp in Willapa Bay and Grays Harbor for many years, disputed Ecology’s assertion. Patten, based in Long Beach, said little new has emerged since 2015.
“I’m disappointed that politics got in the way of science,” Patten said. “It’s politics because spraying chemicals in Willapa Bay is not a popular sentiment. It doesn’t sound good.”
Willapa Bay and Grays Harbor shellfish farmers grow about 25 percent of the oysters harvested in the U.S. Left unchecked, the shrimp will reduce the harvest by 10 percent a year, Patten estimated.
For decades growers controlled the inedible burrowing shrimp with carbaryl. Imidacloprid was proposed by Patten and growers as a less toxic alternative.
The pesticide has not been used in the U.S. in the manner proposed by the oyster growers. Ecology water quality manager Rich Doenges said tests in Willapa Bay showed that imidacloprid reduced the population of some sediment-dwelling creatures by more than half, potentially disrupting the food chain.
He said that Ecology also was influenced by a 2017 EPA study that assessed how imidacloprid running off farm fields affected aquatic life.
The assessment found imidaclorpid posed a low direct risk to fish, but could pose an indirect risk by harming insects that fish eat.
Rep. Brian Blake, an Aberdeen Democrat whose district includes Willapa Bay and Grays Harbor, said he was disappointed by Ecology’s decision.
“I’m worried many of the growers may not survive,” said Blake, chairman of the House agriculture committee. “It’s not new science that killed the permit, it’s new politics.”
The oyster growers’ association issued a press release through the public relations firm Strategies 360 condemning the decision. “To us, it seems like Ecology has been laying in the weeds, delaying action on our permit application, and politicizing the future of our farms,” association President Ken Wiegardt said in a written statement.
Ecology’s decision becomes final May 14. Until then, the public can comment on it. After that, growers can appeal the decision to the state’s Pollution Control Hearings Board.