Grapevine Nurseries Face Supply Challenge

Viruses make things difficult for vine suppliers who sell to California vineyards

by Paul Franson
sunridge nurseries
Steve Maniaci, general manager at Sunridge Nurseries (where he is pictured above, at far left), said that his company planted 55 acres of rootstock in 2012, and he expects to have rootstock that can be used for future field grafting available in 2014.
Yountville, Calif.—The Napa Valley Grapegrowers held the second in a series of Sustainable Vineyard Practices seminars April 24 in Yountville. The session of most interest focused on nursery vines for planting and replanting, and moderator Remi Cohen from Cliff Lede Vineyards started the discussion among a panel from leading nurseries by raising the problems growers face due to high demand for vines to plant—and a recent explosion of grapevine viruses.

Leafroll virus, spread by the vine mealy bug, was already a growing problem. A few years ago red blotch (formerly red blotch-associated virus) started sweeping through vineyards in Napa Valley. Because red blotch isn’t fully understood, universities, nurseries and growers alike are struggling to deal with its impact.

Certified stock
Foundation Plant Services, the source of certified vine stock for nurseries to grow, has tested its stock and found very few vines infected with red blotch, yet it can’t supply large quantities of vines tested by the important 2010 protocol yet. And once nurseries get the sample vines, it takes a number of years before they have sufficient plants and then dormant cuttings for sale.

The nurseries report that they have certified rootstocks now, and the virus doesn’t seem to be turning up in rootstock, but without certified scion wood, they can’t produce grafted vines for sale.

“All the nurseries got rootstock from FPS at the same time last year,” said Steve Maniaci of Sunridge Nurseries. His company planted 55 acres of rootstock, for example. Maniaci expects to have rootstock that can be used for future field grafting available in 2014. He said that nurseries also are buying FPS-certified clean scions, but only some of the many grape varieties and clones are now available. “Growers will have to be patient.”

Maniaci explained that the certification program supported by assessments on vines is managed by the California Department of Food and Agriculture. “If you want to plant vines to grow more plants (an increase block), it must be inspected by the CDFA, and the plants have to come from the FPS and be managed properly.” One requirement is to plant in land that hasn’t been used for vines for at least 10 years.

Dan Martinez of Martinez Orchards in Winters, Calif., said that bed blotch made the nursery change its testing processes. “Red blotch isn’t defined yet, so CDFA can’t certify that vines are free of it now. We’re not sure what testing is best. We’ve gotten different results on the same vine from different labs.”

Like the other nurseries, Novavine Grapevine Nursery has been testing its vines for red blotch. Diego Barison of Novavine said that it has been testing one third of its vines each year.

Unfortunately, clean material isn’t enough.

‘No guarantee’
Dan Martinez of Martinez Orchards said, “You can start clean, but there’s no guarantee after that.”

“The vine mealy bug is a game changer,” said Sunrdige’s Maniaci, for many suspect it can spread red blotch “It’s a big problem because we know we have to be more cautious. We started testing increase blocks in 2009. We test one-fifth of the vines each year.”

He said, “It’s difficult to understand. Some vines that tested clean for leafroll II exhibited it when planted. We haven’t seen any in rootstock blocks, but see some in scion blocks. I believe the vine mealybug will be an ongoing problem. We need to understand it and solve the problem.” He added, “The question is, ‘Where did we get it?’”

Martinez said they’ve seen red blotch particularly in Bordeaux varieties, but he admits that most of the grafting last year was of those varieties.

Steve Huffman of Vintage Nurseries said his company planted a new block in northern Kern County, and it’s surrounded by orchards without any vineyards for miles. “We’ve seen red blotch from source vineyards on the Central Coast surrounded by other vineyards.”

He’s seen no incidence in rootstocks.

Sunridge hasn’t seen red blotch on its primary block in Bakersfield, but he has found it on vines used as sources. “We’ve even found red blotch in some vines that didn’t exhibit it,” said Maniaci.

As far as availability of vines, Barison of Novavine expects some fully certified green vines to be available in 2015 with scions in the following years.

The tissue culture used to clean vines of viruses removes them all, but concern about red blotch has pushed other diseases like crown gall and black goo into the background. Maniaci admits that there’s no telling what the next disease will be.

Growing trends
The panel was asked what growers are looking for, too. Maniaci said that among rootstock, 1103 Paulsen is in most demand with 101-14 and 110R losing popularity.” Freedom is popular for high yields in the Central Valley.”

Martinez believes the solution is to breed resistant plants, as in Andy Walker’s program at UC Davis.

None address red blotch yet, but Maniaci said that Walker’s GRN rootstocks, which are resistant to some nematodes and phylloxera, are starting to find use. Sunridge only planted small blocks until it could gauge the demand. He asked growers for feedback on their results using the new rootstocks.

Not surprisingly, Cabernet Sauvignon is the most requested scion, with Pinot Noir coming in second, Maniaci said.

Martinez observed that the demand for grafted vines was fairly steady at 20 million plants per year for many years, about replanting maintenance level, but the big new demand in the past two years could cause problems: “During the last boom, people planted many of the wrong vines and in the wrong places.”

Huffman reminded the audience to order early. “The problem is finding clean scion material.”

Maniaci added, “Nurseries can’t supply enough budwood when a boom develops, and some growers take scion wood from their own vines. It may not be clean, and likely not certified.” His nursery keeps that wood separate from certified materials. “We tried to get the growers to test their vines before shipping them to us, but that didn’t work. They were in too much of a hurry.”

Funding research
Under present conditions, however, Martinez said he wouldn’t accept grower budwood unless it was tested. He also made a call for money for research. “The grape business is not putting enough money into basic research. The tree nut community spends far more to improve their stocks. We need to spend more on breeding and addressing our problems.” He suggested broadening the fund to fight Pierce’s disease further into other problems.

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