After neurotoxin controversy, oyster growers aren’t spraying to kill shrimp. But herbicide applications to kill nonnative eel grass are still allowed.

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When coastal oyster growers recently backed off plans to spray a neurotoxic pesticide to control ghost shrimp, it didn’t mean that all spraying in Willapa Bay came to a halt.

Shellfish farmers are still allowed to treat commercial clam beds with a common herbicide to kill a nonnative form of eel grass. Last year, 284 acres were sprayed. This year, nine companies — including Taylor Shellfish — notified the Washington Department of Ecology (DOE) that they intended to spray nearly 2,000 acres during the permitted window between April 15 and June 30.

Shellfish growers say Japanese eel grass makes it hard to grow and harvest clams. The thready plant was likely introduced to Willapa Bay in the 1920s, when growers imported Pacific oysters from Japan to replace decimated stocks of native Olympia oysters.

The Manila clams farmed in Willapa Bay are also not native to the Pacific Northwest.

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The pesticide being used, imazamox is approved for aquatic environments and is often used to kill vegetation in irrigation systems. It’s not toxic to animals, and the Environmental Protection Agency considers it so benign that there’s no limit on the amount that can be present in food.

Still, Washington’s Department of Natural Resources and other agencies pointed out during a review process that Japanese eel grass provides important habitat for fish, waterfowl and other species, and said they were concerned that the spraying would also harm native eel grass.

Aerial application is not allowed, and 10-meter buffers are required around each treated plot, said the DOE’s Nathan Lubiner. After three years, he said, the agency will review monitoring reports to gauge the impact on native vegetation.