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Hop stunt viroid research


Hop stunt viroid does just as its name implies; it stunts the growth of hops, leading to smaller yields.

Brewers use the acids found in hop cones to flavor and preserve beer.


Infra-red photo of commercial hop garden. Hop stunt disease infected the plants in rows 8 through 34.

This aerial photo of a commercial hop yard shows just how much HSV can stunt the hop plants’ growth.

Researchers took the picture using a false color infra-red camera about one week before harvest.

The red indicates vegetation while the turquoise color represents soil.

The numbers of plants in each row are the same. All the hops were planted at the same time and grown in the same way.

Yet the plants in rows 1 through 7 have grown so big and thick that it’s difficult to see the ground.

The plants in rows 8 through 34 came from a different source. The hop bines grew shorter with fewer leaves. That’s why you’re able to see more of the turquoise color that indicates soil.

Inside these hop cones is where you’ll find the acids used in beer brewing

“We first spotted hop stunt disease in 2004,” CPCNW’s Dr. Ken Eastwell says. “By 2005 evidence suggested the disease was being spread when new plants were propagated from hop stunt infected plants.”

Data gathered from hop research plots indicates hop stunt disease not only reduces yield, but it 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.

Stopping hop stunt viroid is economically important. The U.S. hop industry supplies one-third of the world’s annual production of hops.

Over 70 percent of each year’s crop is exported to over 60 countries. Pacific Northwest commercial growers produce an annual farm-gate value exceeding $200 million.

Jeff Bullock will research hop stunt viroids interactions with other hop viruses

Graduate student Jeff Bullock’s research will look at how hop stunt viroid interacts with infected hop plants.

“We want to know if hop stunt viroid somehow silences the plants natural defense mechanisms,” Jeff says, “or is it simply able to evade plant defenses similar to cancerous tissues.”

Jeff’s research will also 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.

Researchers use tissue culture to grow plants free of viroids and viruses



Jeff works with Tissue Culture Specialist Martin Joseph to eliminate all the viruses and viroids from test hop plants.  That way they’ll know that any effects they observe will be the result of only what they infect the plant rather than some pre-existing infection already in the plant.

Jeff’s research is in its preliminary stages. Check back to see how Jeff’s research is progressing.

Photo courtesy USA Hops

Hops are bines not vines.     Vines use tendrils or suckers to climb.  Bines climb by coiling around a support.  In a commercial hop yard those supports are twine suspended from a 16 to 20-foot-tall trellis system. The stems of the hop plant have downward-pointing bristles that aid the plant’s grip.

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