An aquatic pesticide that has pitted shellfish growers against environmentalists has been ruled “too risky” for Washington’s waters, the state Department of Ecology said Thursday.
The neonicotinoid pesticide imidacloprid has been linked to several environmental concerns, including that it can hurt fish and birds by killing their food sources.
In 2017, shellfish growers in Willapa Bay (the bay formed by Washington’s Long Beach peninsula) and Grays Harbor asked the state for a permit to spray the pesticide on oyster and clam beds to control native burrowing shrimp.
The Ecology Department put the permit on hold in April 2018 while it reviewed public input and scientific data. The permit now has been denied.
“Mounting scientific evidence confirms the harm from this neonicotinoid pesticide poses too great a risk to Washington’s environment,” the agency said in a statement.
The decision can be appealed to the Washington State Pollution Control Hearings Board.
The Willapa-Grays Harbor Oyster Growers Association has been vocal in its support of using imidacloprid. Its associated website, “Protect Willapa Bay,” notes the two bodies of water produce 25 percent of the nation’s oysters.
Oysters grow in water on top of the sediment that lines the bottoms of bays. Unlike clams, they die if they sink into the sediment.
Burrowing shrimp, also called ghost shrimp, can destroy the firmness of the mud, causing oysters to sink to their deaths. The shrimp are not considered edible.
The state received more than 3,000 public comments regarding the use of the pesticide. It reviewed more than a dozen new scientific studies pointing to negative environmental impacts of neonicotinoids.
The Ecology Department said governments from Canada to Europe plan to phase out agricultural and most other uses of imidacloprid over the next five years.
The agency estimated five acres of tideland are affected by each acre treated with imidacloprid and can persist for months.
The pesticide can affect worms, crustaceans — including a high mortality rate for Dungeness crabs, the Ecology Department said.