WSU scientist: Denied pesticide, oyster growers face disaster

Washington State University research scientist Kim Patten holds burrowing shrimp taken from Willapa Bay. The shrimp undermine the mud underneath oysters, causing them to sink and suffocate. The state Department of Ecology has rejected a plan to spray the shrimp.

Southwest Washington oyster growers face an economic emergency after being barred from spraying a pesticide into Willapa Bay and Grays Harbor, a Washington State University research scientist said Friday.

Kim Patten, stationed at WSU’s research station in Long Beach and an ally of the growers, said the neonicotinoid insecticide imidacloprid was the only practical way growers had to control ghost shrimp. The shrimp burrow in tide flats and cause oysters to sink in the mud and suffocate.

“I don’t see anything else on the horizon that will work at the level growers consider useful,” Patten said. “One of the real threats is the loss of family farms.”

The Washington Department of Ecology announced Thursday it won’t issue a permit to the Willapa Grays Harbor Oyster Growers Association to spray 500 acres. The department said there was mounting evidence that imidacloprid would harm such species as Dungeness crabs and disrupt the food chain for fish and birds.

The shellfish industry is the largest private-sector employer in Pacific County. A University of Washington study found that growers produced $12.2 million worth of oysters in 2013.

The growers association, representing a dozen farmers, said Friday it will appeal Ecology’s denial to the Pollution Control Hearings Board.

The association accused Ecology of bowing to opposition to pesticides and “hiding behind” moves in Europe and Canada to ban imidacloprid over concerns that neonicotinoids applied to land crops harm bees.

“This decision and the glacially slow process that produced it were clearly driven by the political winds of the moment,” the association’s president, Ken Wiegardt, said in a written statement.

In 2015, Ecology issued the growers a permit to spray 2,000 acres. The growers abandoned the plan because of activist, consumer and media backlash. The growers scaled back the proposal, but found Ecology less receptive this time.

The department noted that the European Union banned imidacloprid in April and Health Canada this month proposed phasing it out for agricultural use. The Environmental Protection Agency expects to finish reviewing imidacloprid next year.

Although imidacloprid is widely used on land, Patten said that as far as he knows imidacloprid has not been used in aquatic applications. It was meant replace carbaryl, which growers gave up in 2013 after using for 50 years.

Registering imidacloprid to spray in water took a decade, Patten said. “When we started this process, this chemical did not have a bad rap,” he said. “We were basically stuck with that chemical or none.”

Ghost shrimp and mud shrimp are native species collectively called burrowing shrimp. A parasite has sharply reduced the West Coast population of mud shrimp. Ghost shrimp are not affected by the parasite.

Patten said the number of ghost shrimp is growing dramatically in Willapa Bay. The shrimp are found elsewhere, but are particularly troublesome in the bay because of the number of oysters grown there. “Everybody has lost ground in Willapa Bay,” he said.

Patten has experimented with crushing and blasting out the shrimp, which burrow a meter below the surface. Nothing practical enough to use for an entire farm has emerged, he said. Farmers could erect structures to raise oysters above the surface, but that would be expensive and mean putting lots of plastic in the bay, he said. “Nobody has a viable answer. If it were easy, an answer would have been found out in 70 years of work.”

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