Greetings Fodder Folks! I'm often asked if winter is a slow time for me. Even though the vines and trees are taking a much needed rest, fall and winter is the time for us UCCE Advisors to assess the previous season, prepare reports and presentations, and plan for next year's projects. Sort of like making sure the silo is full and the feed hasn't gone bad so you can produce a higher yield next season (my Wisconsin roots, don't you know...).
A full silo means we won't go hungry over the winter.
With a growing amount of knowledge needed to be an effective extension resource, that means attending informational meetings, such as the annual "Current Issues in Vineyard Health" and the Foundation Plant Services (FPS) annual "Grape Advisory Committee" meetings, both held in Davis last week.
At those meetings, Dr. Maher Al Rwahnih, Director of the Diagnostics and Research Lab at FPS at
UC Davis, presented his work on a recently discovered virus named Grapevine Pinot Gris Virus (GPGV). First identified in 2012 by researchers in Trentino, Italy, Maher is studying the virus presence in California. He has found the virus in asymptomatic and symptomatic vines. In all symptomatic, GPGV positive vines, Grapevine Fanleaf virus was also present. So far, the symptoms appear similar to those of fanleaf: chlorotic mottling, leaf deformation, and shoot stunting.
Dr. Maher Al Rwahnih, Laboratory Director at FPS, is working to better understand Grapevine Pinot Gris Virus
Maher, working with UCCE Farm Advisors, has tested samples from 10 grape growing counties and, so far, has only identified the virus from Napa. In Napa, GPGV has been isolated from Chardonnay, Pinot Noir, Zinfandel, Malbec, Merlot, Cabernet Sauvignon, as well as other varieties.
It appears an eriophyid mite may be a vector of GPGV. Eriophyids are tiny, tiny mites, and there are several "strains" of eriophyid mites affecting grapes. One of these strains infects grape leaf hairs, producing blisters on the top of the leaf and a distorted mat of fibrous leaf hairs on the leaf bottom. I have seen eriophyid mite damage here in the foothills, particularly in home vineyards where no sulfur has been used. Sulfur effectively controls
Symptoms of Grapevine Pinot Gris virus appear similar to fanleaf and, so far, has been found present as a mixed infection with fanleaf virus. (Photo: M. Al Rwahnih).
Eriophyid mite damage brought in to my office this spring from backyard Thompson Seedless.
Unlike Red blotch and leafroll virus, the best time to sample for GPGV is in the spring. I will be surveying foothill vineyards and sending samples for testing to Maher in spring. If you think you might have Pinot Gris virus, and would like your vineyard tested, please contact me! All results will be kept confidential. This is not a quarantined pest so the testing and information is only to improve our understanding of the disease.
Until next time...and thanks for sticking with me!