PROSSER, Wash. – In order to grapple with the wine grape industry’s rising concern–how to deal with grapevine leafroll virus disease–a small group of wine grape growers, and representatives throughout Washington, Oregon and Idaho departments of agriculture, gathered at WSU’s Irrigated Agriculture Research and Extension Center.
 
“Virus diseases like grapevine leafroll are firmly rooted here,” said Naidu Rayapati, WSU grape virologist. “It’s time to face reality and develop strategies to mitigate the problems caused by viruses.”
 
The world-wide grapevine leafroll disease can cause a marked decline in grapevine vigor, grape quality, and productivity. The disease can reduce yields as much as 50 percent or even more, depending on the severity of infection.
 
The meeting was a part of a series organized to examine the current situation regarding virus disease problems in wine grapes. It also helped to develop a coordinated approach at the regional level to confront the challenges ahead and translate ideas into action.
 
“If appropriate measures are not taken, the disease could have direct impact on the sustainability of the wine-grape industry in the state,” Rayapati said.
 
It was estimated a few years ago that 10 percent of Washington’s vineyards have grapevine leafroll disease. Today’s evidence suggests the disease is more wide spread than previously assumed.
 
“No doubt that grapevine leaf roll disease is a serious threat, if not contained,” said Gwen Hoheisel, WSU Benton and Franklin County Extension educator. “The problem has been with us even before we realized, but it is something we need to learn to manage for the prosperity of the wine-grape industry. And the sooner the better.
 
Rayapati’s research has documented grapevine viruses occurring as single or mixed infections. “Knowing what is out there is part of dealing with the problem,” said Rayapati. “This information is critical for designing appropriate strategies to tackle virus diseases in our vineyards.”
 
Leafroll-virus infected vines must be replaced, as there is no treatment for the disease. While some growers are aggressively pulling infected vines at the first sign of disease, others are not.
 
“It’s not everybody’s practice,” said Hoheisel. “Your first line of defense is to remove the infected vine and re-plant in that spot with a virus-free cutting. If your entire vineyard is infected, that is a different decision a grower has to make.”
 
The best insurance against the disease is to plant material that is certified to be virus free, Rayapati said.
 
A shortage of certified planting material may tempt growers to take shortcuts, by bringing cuttings from outside the state or using cuttings from existing vineyards.
 
However, if growers buy certified material from other states, Rayapati warned that growers should be aware of what viruses have been tested, as not all certified material is tested for the same viruses.
 
“Certification has no real value if the cuttings are not tested for all currently known viruses using state-of-the-art technologies,” Rayapati said.
 
For more information on grape leafroll virus, visit http://wine.wsu.edu/virus.
 
For more information on Rayapati’s virology research, visit http://winegrapes.wsu.edu/virology/.
 
For more information on WSU’s efforts to provide growers with certified virus-free planting stock, please visit the Northwest Grape Foundation Service Web site at http://nwgfs.wsu.edu/.