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Posted 22 April 2011. PMN Crop News.

Washington State Gets Hopping to Fight Plant Diseases Threatening U.S. Hop Production

Source: Washington State University Press Release.

Pullman, Washington (April 6, 2011)--Some of the world’s most sought after hops, the ingredient that flavors and preserves America’s favorite brew, are grown in the Pacific Northwest. But a threat to commercial hop production could stop the industry dead in its tracks. Informed beer drinkers everywhere are thus raising a toast to Washington State University, the home of a new federal program providing the industry with the research needed to stop the threat.


The headquarters for the National Clean Plant Network for Hops (NCPN-Hops) is WSU’s Irrigated Agriculture Research and Extension Center in Prosser. The focus of the program is identifying and eliminating diseases caused by virus-like agents, especially hop stunt disease.

Hop stunt disease does just what its name implies: it stunts plant growth, resulting in smaller yields and a stunted bottom line. That has an economic impact on the Pacific Northwest where commercial hop production is concentrated. The U.S. hop industry supplies one-third of the world’s annual hops crop. Over 80 percent of each year’s harvest is exported to more than 60 countries. Pacific Northwest commercial growers produce an annual farm-gate value exceeding $200 million.

“We first spotted hop stunt disease in 2004,” said WSU plant pathologist Ken Eastwell. “By 2005, there was evidence that the disease was being spread when new plants were propagated from hop stunt-infected hops.”

Hop plants undergoing heat therapy to remove viruses.

Hops producers needed to know that the hops being planted in their hop yards were not infected with the disease. So they turned to WSU, which also runs virus elimination programs for fruit trees and grapevines. All the WSU clean plant programs are funded through the U.S. Department of Agriculture’s National Clean Plant Network.

The NCPN-Hops’ focus is on identifying and eliminating hop stunt and other yield-robbing viruses. Data gathered from WSU’s hop research plots indicates hop stunt not only reduces yield, but also the alpha and beta acids found in hop cones. These acids are the sought-after flavor components that give beer its refreshing bitterness.

So far the NCPN-Hops program has produced 22 virus-free selections of the most economically important hops. Those plants are being propagated and distributed to eager hop growers. The program continues to work on cleaning up several other varieties and expects to release at least five selections every year.

More information about WSU’s collaborative effort to increase the economic sustainability of specialty crop production in the United States is available at

Terri Reddout
Program Coordinator