Losing a vineyard to disease is “extremely painful,” says Adam Tolmach, cofounder of The Ojai Vineyard. In 1981, he planted more than five acres of mostly Syrah on Ventura County land that his grandfather purchased a half-century earlier. His last vintage was in 1995.
“You put your heart and soul into it,” says Tolmach. “I planted every one of the vines and nurtured them. It was like my baby that I was working on. It was very heartbreaking to have it slowly die off.”
The culprit was Pierce’s disease (PD), which is spread by insects known as glassy-winged sharpshooters. It’s one of the few scourges that actually kills vines, rather than just hamper them. A problem in California since the dawn of commercial grape-growing in the 1880s, PD is more prevalent in Southern California. But it’s also known to hammer vines in the north, especially along riparian corridors like those near the Napa River.
“We were getting eaten alive by Pierce’s disease in the mid-1990s,” says Doug Fletcher, who worked for Chimney Rock Winery in Napa from 1986 until his retirement in 2019. “The next cycle is on its way up again. You’re seeing more Pierce’s disease now than we have in a long time.”
With climate change marching forward, it’s only going to get worse.
“As your nighttime temperatures warm up, Pierce’s disease will spread further because it relies on mild conditions,” says Tolmach. “Pierce’s disease is going to become a bigger and bigger problem as California weather gets milder.”
But the cavalry is coming, in the form of hybridized, PD-resistant grapes developed by Dr. Andrew Walker at the University of California, Davis.
At the annual Unified Wine & Grape Symposium, held virtually this year in January, Walker was joined by Tolmach and Chuck Wagner, the founder of Caymus Vineyards. Both are growing and now making wines from these new varieties.
Attendees tasted two of Tolmach’s white wines made from hybrid grapes (one called Ambulo Blanc, the other Caminante Blanc), two reds (one named Walker Red, the other Paseante Noir), and multiple vintages of Wagner’s wine made from Paseante Noir.
The wines were a pleasant surprise to many who had previously tried funky or flavorless wine made from hybrid grapes. They had familiar yet unique flavors, ample acidity and appropriate mouthfeel.
Though Walker believed these grapes might be planted in problem areas along a creek as a buffer to PD and used for blending, the results promise a more prominent role.
“We’re pretty ecstatic about it,” said Wagner during the symposium as attendees sipped his rich, black cherry-fruited, mocha-spiced 2019, and fresher, black raspberry-laced, herb-inflected 2020. “We think it’s high-caliber vinifera wine. It doesn’t need to be squeezed along the creek. It can go right into large production. It’s that good, at least in my mind.”
“I’ve never been all that thrilled by the [hybrid grape] releases of the last 50 years,” says Tolmach, whose white wines showed melon, guava, grass and lime flavors. “Some have been O.K., but just not truly exciting. With Andy’s grape varieties, from what I have tasted, there is something really there that is thrilling.”
Walker, a faculty member of the Department of Viticulture and Enology at UC-Davis since 1989, is a prominent name in grape breeding. His rootstock work saves vintners from diseases like fan leaf and infestations of harmful nematodes, and he’s been working on PD-resistant vines for 25 years. He’s proud of these latest grapes, but he believes they’re just the start to address the titanic issues the wine industry will face.
“PD is the last of our problems,” says Walker. “The reality is that we’re going to have to change what we grow and where we grow it as the climate changes, and we don’t know how to do that yet. It looks like it will happen faster than we thought, and be more intense than we thought.”
Over the course of his career, improvements in genetic science and viticultural techniques have enabled hybrid grapes to be grown more quickly and be immediately analyzed for positive characteristics.
“We know enough about the biochemistry of aroma, color and taste to start making decisions,” says Walker, who tracks the DNA markers on each hybrid. “It can be much faster than traditionally.”
But it still takes at least two years to get fruit to ready to test, and hybridizing grapes in this natural way produces mostly throwaway results.
“If you cross Cabernet Sauvignon and Zinfandel, you don’t get a wine that tastes like half-Cab and half-Zin,” says Tolmach. “You can get anything. What you get is unknown.”
With five PD-resistant varieties now on the market, Walker is focusing his research on creating a vine that’s resistant to powdery mildew, a fungus that also affects grapevines throughout the state. Vintners control mildew with a variety of applications that require a lot of time, money and energy.
“It’s the reason that you drive the tractor through the vineyard five to 10 times each year,” says Tolmach. “If you could eliminate that, it would be an incredible economic boon, for sure.”
Walker sees his hybrids as just part of the strategy, which also includes efforts to plant existing heat-tolerant varieties and the exploration of cooler regions for future vineyards. He knows that breeding can bridge a wide gap, however, so long as the public accepts these hybrids.
“There’s been a widely held distaste of breeding new wine hybrid varieties,” said Walker during the symposium. He lamented that the wine industry clings proudly to ancient varieties, whereas the rest of commercial agriculture constantly introduces hybrids that fight disease, increase yields and improve quality.
“There is a new table grape every year, and yet we don’t really see that in wine grapes,” he said. “We’re going to have to do that.”
“PD is the last of our problems. The reality is that we’re going to have to change what we grow and where we grow it as the climate changes, and we don’t know how to do that yet.” —Dr. Andrew Walker, University of California, Davis
The responsibility to convert the public is on wineries. “It’s the marketing department’s job,” said Walker. “Somebody has to take the bull and say we’re gonna push this forward.”
Tolmach is grappling with that right now. Recently, he bottled his 2019 hybrid wines by blending the two whites together, and same with the two reds. He needs to figure out what to call the finished wines.
“It will be a little complicated to introduce people to these new varietals,” says Tolmach, who believes many customers will initially opt for his Pinot Noirs, Syrahs or Chardonnays over something new.
But he’s emboldened by the early success of these grapes. “The Pierce’s-resistant varieties will stand up to climate change,” he says. “And they’re handling the problem in an environmentally friendly way, which is not using insecticide to stave off this pending disaster.”
In addition to the acre-plus he planted in Ojai, Tolmach hopes to plant more hybrids at Fe Ciega, a vineyard he just purchased in the Sta. Rita Hills in Santa Barbara County. Though the property’s Pinot Noir sits safely on a high ledge, a small block of Chardonnay along the Santa Ynez River was decimated by Pierce’s disease a few years ago.
That’s where these PD-resistant vines will go. Tolmach is excited to see what cooler-climate versions of these grapes will produce.
Most of all, he’s just happy to have a working vineyard back at his family ranch. “We’re excited about being able to grow grapes here at our place in Ojai again,” he says.
Last Updated: May 8, 2023