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Nematode found in Washington; quarantines unlikely

PULLMAN, Wash. – A close relative of the cereal cyst nematode was discovered in Washington for the first time this summer. Scientists don’t believe quarantines will be required but are assessing the significance of the discovery.

“We’ve been dealing with a similar nematode for several years,” said Timothy Murray, a plant pathologist at Washington State University. “This new species will have a comparable impact to the existing one and we’ll use the same treatments for its control.”

A stunted patch of winter wheat in a field infested by Heterodera filipjevi near Colton, Wash.
A stunted patch of winter wheat in a field infested by Heterodera filipjevi near Colton, Wash.

Richard Smiley, an Oregon State University professor, discovered the same species, Heterodera filipjevi, in Oregon in 2008 and was responsible for the find in Whitman County, Wash.

The nematode is listed as a quarantine pest by the U.S. Department of Agriculture’s Animal Plant Health Inspection Service. The agency can potentially prohibit farmers from planting susceptible crops in infected fields. The pest affects wheat, barley, oats and other wheat-like grasses.

However, Murray doesn’t think quarantines will be required. He is in close communication with the inspection service to develop appropriate responses.

The recommended treatment for the pest is crop rotation and nematode-resistant wheat varieties. These practices keep nematode numbers low, thus reducing damage.

“These nematodes are significant pests around the world,” Murray said. “But there isn’t really a reason to quarantine fields in Washington since the nematode is already established and our farmers know how to manage them.”

Once nematodes are present, they are difficult to eliminate. Since they can’t grow on peas or lentils, significant numbers die during crop rotation.

Murray said quarantine is useful in areas where a pest is newly introduced and could be prevented from spreading. But since this nematode already is established in Washington fields, quarantine is unlikely to be effective.

“We estimate the new pest was introduced 10 to 15 years ago,” he said.

He also said Smiley’s research has shown that yield losses due to cereal cyst nematodes rarely exceed 10 percent, with a conservative estimate that nematodes do around $3.4 million in damage each year.

Murray said more surveys are needed to see how far the species has spread. The better the pest can be tracked, the more accurate the response for and from farmers. Smiley found three locations but did not look outside Whitman County.

More information is available on the WSU Extension small grains website at

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