‘Red Blotch like phylloxera for California’

Grape vine virus Red Blotch could be as damaging as phylloxera to Californian vineyards, believes Bruce Cakebread of Napa’s Cakebread Cellars.

Red Blotch was discovered in Napa Valley in 2008. Photo credit: Washington State University

Following a tasting in London on Tuesday this week, Bruce Cakebread discussed some of the issues facing wineries in California, in particular drought conditions and their affect on wine style, before mentioning Red Blotch as the biggest problem for growers in the region at the moment.

Having told db that he has already pulled out 22 acres (9 hectares) of Cakebread vineyards due to the virus, he said there are “a lot of vineyards being ripped up now and being re-planted with virus free vines”.

And, suggesting that there was a lot more replanting still to take place, he said, “We think Red Blotch is the next big issue for California, and the impact is like phylloxera in the late 80s and early 90s – Red Blotch is the one that’s coming up.”

During the 1980s a new type of phylloxera started to attack vines in California that were planted on the ARx1 rootstock, which was previously believed to be immune to the parasite that had devastated European vineyards in the late nineteenth century.

So, by the mid 90s, in Napa and northern California, as many as half the total area of vines had been destroyed.

Red Blotch was discovered in the US in 2008 by researchers from the University of California, Davis, who found the virus in Cabernet Sauvignon vines at the Davis Oakville Station Experimental Vineyard in the Napa Valley.

Cakebread said that currently there is no treatment for the virus, which, as its name suggests, causes the vine’s leaves to develop red blotches.

Affecting the vine’s ability to photosynthesise, Red Blotch can cause sugar levels to drop by as much as six degrees (Brix), while reducing yields, and in red grapes specifically, the colour and tannin levels.

Cakebread said that the virus was most common among vineyards planted around 25 years ago when it’s possible growers were planting or grafting with virus-infected material, adding that the spread of Red Blotch was not the result of pruning methods.

Furthermore, stressing the concerning nature of the situation, he said that the exact cause of the virus had yet to be determined.

Cakebread told db that he expects to pull out more of the winery’s 510 acre-estate due to Red Blotch, replating with virus-free material on newer rootstocks that are more resistant to nematodes.

He also remarked that the diseased vines were being used to help the new plantings. “We are making bio char out of the vines and mixing it with compost, which we then spread on the vineyard, so the old vines are helping the new ones,” he said, adding that the use of bio char in the soil means that Cakebread can use less water and nutrients.

He also identified a further benefit from virus-infected vines, noting that their removal had given him the chance to change the row direction of his vineyards to “eliminate heat issues”.

As previously reported by db, Bruce Cakebread is making changes in the vineyard and cellar to lower alcohol levels in his wines, which have gradually risen due to increasingly dry conditions in California.