Addressing industry concerns about the spread and effects of Grapevine red blotch-associated virus (GRBaV), the American Vineyard Foundation (AVF) awarded more than $200,000 in research funds for its 2013-14 grant cycle for several projects to study the issue. The award amounts and projects include:
• $69,600 for “Biology and Spread of GRBaV,” to lead researcher Dr. Mark Fuchs of Cornell University.
• $38,300 for “Evaluating the Effects of GRBaV on Symptom Development and Fruit Maturity,” to lead researcher Rhonda Smith, UC Cooperative Extension viticulture advisor for Sonoma County.
• $75,000 for “Development and Application of Next Generation Sequencing to Facilitate the Release of New Grapevine Accessions in Quarantine and Certification Programs,” to lead researcher Dr. Adib Rowhani of UC Davis Foundation Plant Services.
Red blotch disease, caused by GRBaV, shows vine symptoms similar to leafroll disease with discolored grape leaves in fall and reductions in grape sugar levels. Vines infected with GRBaV have been found in California, New York, Virginia, Maryland, Pennsylvania, Texas and Washington. The virus can be graft transmissible, and it appears it can be spread from infected vineyards to neighboring uninfected vineyards, so vector transmission research is a high priority.
Related to the vector issue, AVF awarded $28,600 to Dr. Kent Daane, entomologist at UC Berkeley for research on “Virginia Creeper Leafhopper (VCLH) Control.” Some leafhoppers, and VCLH (Erythroneura ziczac Walsh) in particular, are believed to be vectors of GRBaV. In a recent study by researchers at Washington State University in Prosser, WA of what they call grapevine red leaf associated-virus, that is almost identical to GRBaV, the virus was transmitted by the VCLH from grapevine to grapevine under greenhouse conditions. A paper on this research was published June 5, 2013 in PLOS ONE, a peer-reviewed, open access online journal.
The Virginia creeper leafhopper is native to the Northern Midwest and is found in Midwest and Eastern U.S. vineyards, and in vineyards in British Columbia and Washington. It was first identified in California in the late 1980s and is now found in Mendocino and Lake Counties, the Northern Sierra Foothills, and Northern Sacramento Valley. The VCLH is similar in appearance and in its life cycle to the native Western grape leafhopper, and can be controlled with the same types of pesticides, but it is not controlled by the same parasitic wasps as the Western grape leafhopper.
In related news, the California Department of Food and Agriculture Pierce’s Disease (PD)/Glassy-winged Sharpshooter (GWSS) Board on June 21 deadlocked in a 6 to 6 vote of members present, resulting in no action, on designation of GRBaV as a new pest for Board study and potential funding for research and outreach. The vote was divided mostly along regional lines, with most grapegrower representatives from the San Joaquin Valley opposed to designation, while representatives from other grapegrowing regions supported designation. GRBaV is present, and a larger concern in North Coast vineyards, whereas, it is not currently a serious issue for Central Valley grape growers.
The PD/GWSS Board was scheduled to vote on GRBaV designation at its last meeting April 29, but delayed the vote in part to await outcome of the announcement of research funding from AVF. Some Board members believe the AVF research can sufficiently address current needs. Others argued that given the current level of industry concern, GRBaV should be designated as a pest now, which does not obligate the Board to allocate any funds, but would enable the Board to be ready to take action if necessary.
The Board received authorization, following 2009 legislation and the 2010 grower referendum to use assessment funds for research and outreach on other serious pests and diseases of winegrapes, as long as such funding does not interfere with PD/GWSS control and research efforts. To date, only the European Grapevine Moth (EGVM) has received Board designation, and its eradication program received Board funding for outreach activities. As some Board members pointed out, the investment to fund temporary EGVM grower outreach coordinators in key counties resulted in a significant bang for the buck as the EGVM has been declared eradicated in most of those locations, and the Board no longer has current or anticipated needs to fund EGVM projects.
As a result of the tie vote, the issue could be revived at a later meeting. Some members indicated that if new developments or information regarding GRBaV raise the issue to a more serious level, the Board could mobilize fairly quickly to designate the disease and assist the industry with research or outreach funding.