(Wines&Vines) - Grapegrowers have a new virus to worry about, though it’s not yet clear how big a danger it is to wine grape yields or quality.

The grapevine Pinot Gris virus (GPGV) recently was identified in a number of Napa Valley vineyards after being discovered in vineyards from Korea to Canada, and widely in the Mediterranean region.

The virus was the topic of one of the sessions at the second Sustainable Vineyard Practices seminar on Pests & Diseases organized by the Napa Valley Grapegrowers, University of California Cooperative Extension and the Napa Valley Vineyard Technical Group (Vit Tech).

The seminar was held in the auditorium of Copia in Napa, the first return of the sessions to the long-closed facility since its acquisition by the Culinary Institute of America.

Napa County viticulture advisor Dr. Monica Cooper gave the presentation for Dr. Maher Al Rwahnih, associate plant scientist for Foundation Plant Services at the University of California, Davis, who couldn’t attend. The following summary is based on the presentation and Al Rwahnih’s notes.

Only identified recently

The symptoms of the grapevine Pinot Gris virus—chlorotic mottling, leaf deformation and stunting—were first noticed in vineyards in Trentino (northeastern Italy) in 2003. It was identified in 2012 by high-throughput sequencing as a new member of the Trichovirus genus. (See “A New Disease in Italian Vineyards.”)

The new virus was found not only in Pinot Gris (called Pinot Grigio in Italy) but also on Traminer (known in the U.S. as Gewurztraminer) and Pinot Noir and subsequently on other varieties including Chardonnay.

The GPGV sequence analysis demonstrated that it was closely related to Grapevine berry inner necrosis virus (GINV) but affected only the leaves, not the berries.

GINV is believed to be spread by the eriophyid mite Colomerus vitis, Pagenstecher.

GPGV has been reported in symptomatic and asymptomatic vines for wine and table grape varieties in many countries, with symptoms appearing on 16 of 17 vines tested, though also found in six of 23 vines that didn’t exhibit symptoms.

The virus has since been found in Trentino, Friuli Venezia Giulia, Veneto, Emilia Romagna and Puglia in Italy, and in Slovenia, the Czech Republic and Slovakia, Greece, France, China, Turkey, Republic of Georgia, South Korea, Canada and the United States.