HOP STUNT VIROID: Hop stunt viroid does just as its name implies; it stunts hop growth leading to smaller yields.
Not only does hop stunt viroid reduce yields, it also also reduces the alpha and beta acids found in hop cones. Those acids are used to give the beer its flavor. In some cases the reduction of acids was as much as 45 percent. Some plants infected with Hop stunt viroid exhibit birght yellow foliage at the base of the plant during early growth.
Stopping hop stunt viroid is economically important.
The U.S. hop industry supplies one-third of the world's annual production of hops. In the Pacific Northwest, commercial growers produce an annual farm-gate value exceeding $200 million.
"We first spotted hop stunt disease in 2004," Dr. Ken Eastwell said. "By 2005 evidence suggests the disease spread when new plants were propagated from hop stunt infected plants." Eastwell is the director of the Clean Plant Center of the Northwest based at Washington State University's Irrigated Agriculture Research and Extension Center in Prosser, Washington.
Another symptom of hop stunt viroid are lime-colored leaves, such as those seen in this picture of Glacier hops.
Research, conducted at the Clean Plant Center of the Northwest, will look at how hop stunt viroid interacts with other viruses that infect hops, such as hop mosaic virus, to see if hop stunt viroid causes the other virus symptoms to get worse or weaker.
Click here to learn more about the practical aspects of managing hop stunt viroid.