$5 million UC Davis project aimed to help wine business fight red blotch vine disease

The 14-year battle against a virus that makes grapevine leaves turn color long before fall and is blamed for sapping the sweetness of wine grapes has taken a toll on a key source for nurseries that supply the North Coast and other regions in California.

But now construction is underway on the first of two planned greenhouses at University of California, Davis, intended to protect grapevine plant material from red blotch and other diseases that could endanger the industry, whose California economic impact is $57.6 billion annually.

The $5.25 million beginning phase is a 14,400-square-foot greenhouse designed with a vestibuled entry to protect against insects from flying or riding inside, bringing with them the pathogens they carry. But the greenhouse on anticipated completion at the end of next year will only be able to make available half the number of vines offered annually from the open-air vineyard at the facility on the Yolo-Solano county border, so another greenhouse would be needed, according to facility officials.

It’s a project of Foundation Plant Services, developed in 1958 by UC and California Department of Food and Agriculture scientists to screen grape and strawberry vines, fruit and nut trees, rose bushes and sweet potato plants for pests and diseases so they aren’t spread through nurseries.

“It’s one great way for viruses to move around,” said Monica Cooper, Ph.D., a viticulture and pest management advisor for the UC Cooperative Extension in Napa County.

In California, the main vector is thought to be the three-cornered alfalfa hopper. In the East, it’s the Virginia creeper leafhopper. The alfalfa hopper has been studied for decades and was investigated then ruled out as a vector for Pierce’s disease, Cooper said. Pierce’s disease is a feared foe in the wine business for its quick action to starve grapevines of nutrients.

The 100 acres of foundation vineyards at UC Davis is the primary source for grapevine plant material distributed to nurseries under the CDFA’s Grapevine Registration and Certification Program, which provides the majority of grapevines planted in the United States.

It’s also the nation’s largest quarantine center for vine materials coming from outside the country, such as choice clones from France. Imported vine materials are tested over two years for one of the 86 known grapevine viruses before being deemed disease-free.

“This is kind of a game changer for us,” said Maher Al Rwahnih, a plant pathologist and director of Foundation Plant Services, about the greenhouse project.

That’s because the Russell Ranch foundation vineyard at Davis, one of the facilty’s two open-air propagation properties, has been suffering with grapevine red blotch virus since it was detected there in 2017, and the spread was found in 52% of the crop picked last fall. No plant material has been sent out from that property.

Tthe other foundation vineyard, called Classic, is the source for the 4,000 cleared vines made available by the program annually. But the virus has been detected in 1% of that vineyard, and program officials fear that could grow.

The second greenhouse, expected to be built in two or three years, would bring the indoor-isolation capacity to 4,000 vines.

The grapevine red blotch virus was first found in a Napa Valley cabernet sauvignon vineyard in 2008. Since then, it has been detected in winegrowing regions in Oregon, Washington, Idaho, North Carolina, New York and Ohio.

A 2017 Cornell College of Agriculture and Life Sciences study estimated losses from grapevine red blotch virus could range from nearly $5,500 per acre in Washington state to $169,000 in Napa Valley, varying by extent of infection, cost of farming and crop value.

Cooper, who was part of that study, said much more has been learned since then about the virus, its impact on vines and fruit, and suspected vectors and their favored host plants.

Funding for the first UC Davis vine greenhouse is coming partly from the California Fruit Tree, Nut Tree and Grapevine Improvement Advisory Board, managed by the CDFA, which contributed $4 million. The California Grape Rootstock Research Foundation gave $500,000, Foundation Plant Services $450,000, and the California Grape Rootstock Commission $100,000.

Jeff Quackenbush covers wine, construction and real estate. Before coming to the Business Journal in 1999, he wrote for Bay City News Service in San Francisco. Reach him at or 707-521-4256.

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