Viticulturists and scientists battle latest vineyard virus: red blotch

When he was hired by Halter Ranch in 2012, Lucas Pope knew there was a lot to tackle. With 283 acres of wine grapes on a more than 2,000-acre ranch — complete with organic walnuts, olives for oil and grazing cattle — it’s the largest vineyard on the west side of Paso Robles, where the mountainous terrain, limestone-like soils, and ocean influence comprise a vintner’s paradise. Plus, the property was in the midst of a major transition from simply selling grapes to becoming its own estate winery, which made the stakes even higher for the new vineyard manager.

What Pope didn’t realize, however, was that Halter Ranch was soon to be on the front lines in the fight against red blotch, the latest grapevine disease threatening vineyards across the continent. “We knew we had something going on, but we didn’t know what it was,” said Pope, who noticed that some grapes wouldn’t get fully ripe and leaves would become red far too early in the season. Then he attended a seminar at UC Davis, where Cornell researcher Marc Fuchs detailed what was known about red blotch, which had just been identified in 2011. “That was the red flag,” said Pope. “It became apparent very quickly that we had a major issue.”

It’s been a “roller coaster” ever since, as Pope and his team scoured the vineyard for sick plants, cooperated with a willing nursery to propagate verifiably clean vines, and steadily replaced the bad with the good. “We’ve redeveloped half the ranch,” said Pope, who’s enjoyed the unflinching support of Halter’s owner Hans Wyss, a conservation-minded billionaire from Switzerland who winced upon first hearing the news but then threw all available resources to the challenge.

“We’re putting our best foot forward,” explained Pope, who’s taking every step possible to ensure that the vineyard is free from all imaginable ills. “It may not be red blotch in the next 10 years, but we’re using all the tools today to make everything as clean as possible now.”

Pope is one of the few farmers not afraid to speak openly about his battle with red blotch, which, if left unchecked, could greatly diminish both the quality and quantity of California wines, from Napa to Santa Barbara counties. Though it’s been around since at least the 1940s — a sample from the UC Davis Herbarium recently confirmed as much — the disease only became a major problem in the 2000s, following a boom in plantings statewide.

That’s when vintners began noticing that their grapes would stall their ripening a few brix degrees short of normal, that yields were dropping, that the vines went red earlier than usual, and that the resulting wines lacked color. “The flavors are way off,” said Fuchs, the Alsace, France-raised professor from Cornell. “And instead of having a dark red Pinot Noir or Cabernet Franc, you have something that looks more like a rosé.”

Those were similar to the symptoms of leafroll virus, a well-detailed condition that’s existed since the dawn of commercial grape-growing, so that’s what the scientists initially thought was happening. “We were all way off,” explained Fuchs, who used to bet money on being able to identify leafroll simply on sight. “I feel like the dumbest scientist trying to identify leafroll versus red blotch. Now I would not take a single bet anymore.” For one, leafroll is an RNA virus spread by vine mealybug, while red blotch infects the DNA and affects different varieties differently — Sauvignon Blanc leaves, for instance, don’t turn red early, and yields aren’t too hampered in Cabernet Sauvignon.

The leading, and really only, suspicion is that infected vines entered the extensive commercial nursery system that growers rely on for new plantings. Since the virus was unknown, it wasn’t tested for, so spread widely as thousands of acres of vines were planted across the country over the past two decades. “That’s the only explanation, and explains why, in such a relatively short time, we find it everywhere grapes are grown here,” said Fuchs, who explained that, typically, when a damaging disease is found, it is isolated at first. “It’s a very unusual situation.”

Today, it’s found in all white and red varieties as well as in hybrid and wild grape species and rootstocks. In addition to North America, the disease is also known in India and South Korea, but not yet in South Africa or Europe. “That’s very puzzling to me,” said Fuchs, who acknowledged that there was a somewhat suspect report from Switzerland.

While Fuchs and others are examining genetic means of protecting plants against leafroll, red blotch, and other diseases — vaccines for vines, essentially — the only way to deal with red blotch right now is to either completely rip out your vineyard or methodically “rogue” it, taking out infected blocks or vines one by one. And when it costs more than $10,000 an acre to rip and $30,000 or so to replant, it’s not a happy solution.

But it’s better than the alternative: a recent study published in the American Journal of Enology and Viticulture said that, when all economic factors are considered, red blotch could reach a $28,000-per-acre annual loss for high-end Napa vineyards. It also recommended complete replanting if a vineyard is more than 30 percent infected.

Of course, grapevine disease is nothing new: California has dealt with phylloxera, which decimated France’s entire industry in the late 1800s, as well as nematodes, leafroll, powdery mildew, and Pierce’s disease, among many others. The latter, which emerged in Temecula in the late 1990s due to the arrival of the glassy winged sharpshooter, a voracious vector, remains a big concern throughout the state.

“That changed the dynamics,” explained Steve McIntyre, who farms 12,000 acres of grapevines in Monterey County and sat on the committee to stop the spread of the sharpshooter. Prior to that, vine diseases were considered more regional concerns, but Pierce’s disease caused growers to rally statewide. “Temecula was devastated, but we were able to keep (the glassy winged sharpshooter) in Southern California,” said McIntyre, who believes the rapid pace of globalization will only make diseases like this more prevalent in the years to come.

Like Pierce’s disease, identifying a vector became an important battle in the red blotch war. It took tremendous and time-consuming efforts — identifying infected vineyards, collecting every nearby bug, and then trying to get those bugs to infect healthy vines — but last year, Frank Zalom’s UC Davis team discovered that the little-known three-cornered alfalfa treehopper was transmitting the disease.

Though he suspects there may be other vectors — there’s at least one other species that seems to be spreading the disease in cooler and hillside areas, whereas the treehopper prefers warmth and pools of water — finding the treehopper was a critical step. “Growers are concerned because if they replant with virus-free stock in an area that has other vineyards nearby that are already infected, what’s the risk of getting it again,” he explained. “That’s why this vector work is so important.”

Both Zalom and Fuchs, who each also works on a variety of other diseases, fruits and vegetables, find this red blotch conundrum to be one of the most fascinating quests of their long careers. For Fuchs, it’s also opened his eyes up to a much more pressing problem: how weak and slow government forces are to combat a problem like this even after it’s been identified.

To date, New York, where red blotch isn’t even a major issue, is the only state that mandates that nurseries test for the disease before selling vines. “Whether it’s vintners, nurseries or regulators, no one will deny that red blotch is hugely important,” said Fuchs. “But working with the regulators is like working with a bunch of turtles — they move in the right direction but it takes so much time.”

Thankfully, Fuchs believes the nurseries are ahead of the game. “Nurseries are not sitting on their rear ends and waiting for regulators to act,” he said. “Most of them are very proactive.”

Like Zalom, he’s also confident this problem can be fixed, though it will take time. “If all the parties sit around the same table with the goal of producing and adopting clean material, I would venture to say that, in less than 10 years, the virus won’t vanish, but it will reach a very low level that will be very easy for the industry to manage,” pledged Fuchs.

And if they don’t? Said Fuchs, with a cautionary laugh, “Then you will have some visionaries who will be winners and a lot of guys who will be left behind and they will deal with the consequences.”