Grapevines in a vineyard in Wapato have been infected with a virus that causes grapes and grape clusters to grow smaller.

WSU virologist Naidu Rayapati, an expert on grapevine diseases at WSU’s Irrigated Agriculture Research and Extension Center (IAREC) in Prosser, first found evidence of the Tobacco Ringspot virus (TRSV) in 2013. He and Andrew Schultz, the vineyard manager, are testing ways to manage or eliminate the disease.

“We are still learning about this problem,” Rayapati said, “and hopefully we are able to come up with some practical strategy for management in the near-future.”

The TRSV is a slow-moving plant virus which does not have any ill-effects on people or animals who consume the plant or its fruits, Rayapati said. The issue is more economical, due to the virus’s effect on crop yield, but Schultz is not overly worried.

“I don’t think there is major issue with plant sources having this stuff,” Schultz said. “I don’t think it’s going to be complete economic disaster.”

The state of Washington boasts a $4.8 billion wine industry, with 60,000 acres of land cultivated for wine grapes alone, according to a WSU News release.

“My message to the growers and the entire Washington State grape and vine industry is to be aware of these kinds of emerging problems,” Raypati said. “And to try to assess potential risks before planting with virus testing materials [on-hand].”

The virus spreads from plant to plant largely through infecting a previously unknown species to Washington, the dagger nematode. These microscopic worms are parasites to plants who spread diseases they may be carrying when they feed from one plant to another, according to the release.

One of the management processes Schultz and Rayapati’s team has investigated includes when to get rid of these dagger nematodes from the soil before they cause real damage to newly planted crops, Schultz said. Through testing on the infected Prosser estate, they have found largely that nematode populations, once exterminated to the extent possible, are almost fully recovered after three years.

Schultz said after two years, the growth of the population begins to have an effect on the newly planted vines. Growers currently deal with nematode populations about every two years once found in the soil.

Questions still remain on the most efficient way to handle this virus once detected, Raypati said. Though there have been no confirmed sightings of this virus in commercially sold crops in Washington, he said he and his team are still working to find solutions.

Correction: This article has been revised to reflect that the infected vineyard is in Wapato, not WSU Prosser.