SALEM, Ore. – Five of six samples taken from geese that died at Staats Lake in Keizer are positive for the rodenticide zinc phosphide, according to results from Michigan State University’s Center for Integrative Toxicology.

Since the first dead geese were collected at Staats Lake on April 11, a total of 67 dead geese have been found. ODFW staff are monitoring the lake almost daily but no dead geese have been found since April 16.

Regulations on zinc phosphide's use are in place to protect wildlife, though it is not clear if misuse of a pesticide product occurred. Zinc phosphide is allowed for use on golf courses and for such crops as wheat, grass grown for seed, nursery products, and berries. The Oregon Department of Agriculture has implemented Special Local Needs Labels (SLNs) that require below ground application on zinc phosphide on grass grown for seed from September 1 through April 30. All pesticide product users are required to take precautionary measures year-round to prevent impacts on wildlife.

The Oregon Department of Agriculture, the Oregon Department of Fish and Wildlife and U.S. Fish and Wildlife Service have been actively investigating the incident since it was first reported. ODA is working with local pesticide dealers to identify recent purchasers of products containing zinc phosphide, which is a Restricted Use Pesticide only for sale to licensed applicators. By interviewing recent purchasers, ODA is attempting to specifically determine how and where these pesticide products have been applied in the vicinity. If ODA identifies an unlawful use, the agency will proceed to take enforcement action.

Zinc phosphide is used to control small rodents such as voles, mice and ground squirrels, particularly in grass fields where such rodents can cause significant damage to crops. It is highly toxic to rodents, birds, fish and other wildlife, although it is not believed to be hazardous to birds of prey that eat rodents that have been killed by it. When zinc phosphide is ingested it is converted by stomach acids to phosphine gas, which acts on the heart, kidney and liver; death occurs from heart and kidney failure. Death usually occurs within 15 minutes to four hours after ingestion of a toxic dose.

Geese, whether resident or migratory, are protected under the federal Migratory Bird Treaty Act. Anyone who finds dead geese or has information on the illegal use of zinc phosphide should contact the Oregon Dept. of Agriculture at (503) 986-4635 or the U.S. Fish and Wildlife Service’s law enforcement office in Wilsonville, (503) 682-6131.