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Pinot Gris Virus in Napa Valley

Pinot Gris Grapes

There are few things that scare winemakers, vineyard owners and growers more than a new virus that effects vines.

Grape vines, are especially vulnerable to new disease, largely for two reasons.

First and foremost, vines tend to mutate incredibly quickly.  Anecdotal evidence tells us this to be true, after all there is a Pinot Noir clone called the Calera clone…..Calera wasn’t planted until 1974.  So a small Pinot Noir vineyard can gain enough genetic diversity in the space of under 40 years, to be considered a new strain of a plant.  In the agriculture business, I’m told that’s pretty remarkable. I’m going to be writing about what used to happen in vineyards and what happens now, in the coming days.

Secondly, too much of the wine industry is a monoculture.  If you drive up highway 29 through Napa, you see rolling hills, trees and other stuff planted, even some of the signs of civilization.  Drive other parts of the state (think the parts making the cheapest wine imaginable) and you’ll notice something different.  These are factory farms.  Not a hair is out of place.  If you think about it though, what if you were a pest that liked eating grape vines? A good spot to be right?

What’s Scaring People?

In the case of this year, something called Pinot Gris Virus has found its way to Napa Valley after propogating itself in Italian vineyards over the past handful of years.

The results to infected plants range from bad, to severe. Leaf motting is the most common (in essence the vine ends up deficient of nutrients), leaf deformation (can lead to many issues, including burned fruit since leaves are trained to block the sun from fruit), delayed vine growth (a serious issue when it normally takes 5 years to get a plant online in the first place) and then reduced yield (presumably without the normal uptick in quality).

How’d Pinot Gris Virus Get Here?

According to Wines and Vines, Pinot Gris Virus is transferred by a small pest, called the erineum mite:

The erineum mite has historically been considered a minor grape pest in California, but its presence has been reported more frequently in vineyards in recent years, including in Napa County and in Central Coast wine grape regions. Erineum mites feed on the underside of grape leaves in spring and summer, causing the leaf to produce blister-like galls on the leaf’s upper surface. Although this is primarily a cosmetic issue on leaves in mature vines, in younger vines, high mite pressure can lead to defoliation.

In essence it sounds like a known pest, has either newly become a vector (or in terms of the animal world, you’ll call them a reservoir like bats and Ebola as an example) meaning that the mite carries the disease, but does not suffer any ill effects, or at least no short term ill effects from the disease.  When the mite feeds on the vine though, the disease gets imparted to the vine itself.

Every major wine region in the world has a period of quarantine for vines coming in to be planted.  Unfortunately, even with that practice in play, a pest or two does make it through from time to time.

Why is it called the Pinot Gris Virus?

Grape vine diseases are generally named after the varietal in which they were first discovered. Pinot Gris Virus was originally found in Italy, on a planting of Pinot Gris.

Why Should you care?

Outside of the standard stuff, like people investing so much time and effort into a vineyard only to have it destroyed by a mite….basically disease for vines in today’s world is a major, major problem and something as simple as Pinot Gris Virus if it propagates well in America, would single handedly increase prices for the varietal because it would shorten the average life span of each vine.


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