Napa vintners pledge $2.5 million for research into grapevine red blotch virus

A growing problem in Northern California

Grapevine red blotch disease, first identified in 2008, has become an increasing concern in Northern California. Rutherford is regarded as a center of infection in Napa Valley, while grower Andy Beckstoffer has removed large sections of the historic Georges III vineyard in an effort to eliminate infected vines. Although the wine-grape surplus has driven much of Napa’s recent vineyard removal, red blotch has also been a major factor.¹

In the Russian River Valley, vintner Tom Rochioli responded to a serious outbreak by traveling through his vineyards on an all-terrain vehicle, marking symptomatic vines for removal. He described his campaign as a fight against both red blotch and the threecornered alfalfa hopper.¹

How the disease damages vines and wine

The disease is caused by grapevine red blotch virus and develops slowly, making it difficult to detect. Unlike phylloxera or Pierce’s disease, it does not rapidly kill vines. Instead, it disrupts their metabolism, suppressing photosynthesis and hindering the movement of sugars from leaves to fruit. Grapes can appear relatively normal at harvest even when the resulting wines are diluted, tart or strongly astringent.¹

Scientists believe the threecornered alfalfa hopper spreads the virus as it feeds on sap, acquiring it from an infected vine and transmitting it to another. Some infections originated in nursery stock, but the disease now moves between neighboring vineyards. Symptoms may take a year or longer to emerge, allowing transmission before growers recognize an infection; in red grape varieties, a principal sign is the reddening of leaves beginning in midsummer.¹

A $2.5 million research initiative

A group of vintners has pledged $2.5 million to launch Phase One of the Grapevine Red Blotch Virus Research Initiative. The public-private collaboration is intended to accelerate work conducted for more than a decade by researchers at the University of California, Davis, and other universities.¹

Owners associated with Dominus Estate, Darioush Winery, Joseph Phelps Vineyards, Colgin, Opus One and Vine Hill Ranch helped launch the project, together with the Araujo family and other participants.¹

Detection, transmission and practical control

The initial research program will seek better tests for identifying infected vines, study the threecornered alfalfa hopper and other possible vectors to find ways of slowing transmission, and assess practical methods that winegrowers can use against the disease.¹

Ben Montpetit, chair of the Department of Viticulture and Enology at the University of California, Davis, said researchers and industry leaders had jointly identified the most urgent research requirements and coordinated the work ahead. He credited the wine community with supplying the resources needed to begin the plan and said the university aimed to help provide growers with practical tools.¹

Rochioli said his own response to the disease had been frustrated by the shortage of reliable knowledge about red blotch and the alfalfa hopper, underscoring growers’ demand for faster answers.¹