What’s the impact of smoke on wine? UC Davis researchers are trying to find out
During the catastrophic wildfires of 2017, smoke inundated vineyards across Wine Country, covering vines in a thick, noxious haze.
Vintners were frantic about how their grapes would be affected, remembered Anita Oberholster, an extension specialist in enology with UC Davis.
“Suddenly, everybody wanted to know everything about smoke,” she said. “Everybody started calling me and asking me, ‘What’s the impact of smoke? What should I be doing?’”
At the time, Oberholster had limited information to guide them. The latest research then on smoke’s impact on grapes came from Australia, which had battled perplexing firestorms.
But that research focused on syrah grapes, widely grown in Australia. It didn’t translate to our region, where farmers grow a broad variety of grapes.
“It was like putting a Band-Aid on a festering wound without antiseptic,” she said of efforts to deal with smoke’s effect here in 2017.
So today, at an 11-acre vineyard in Oakville, Oberholster and other researchers are experimenting, trying to measure the impact of smoke and devise ways to mitigate it, along with the effects of drought and climate change.
Equipped with a $7.8-million federal grant, Oberholster is optimistic the research will yield actionable results.
With more information, in three to five years vintners, growers and crop insurance companies will be able to avoid the chaos and confusion they experienced in 2020 during the LNU Lightning Complex fires, she said.
Those fires began Aug. 17 that year, when most vintners still had fruit on their vines.
Some sent their grapes to labs to be tested for smoke impact, and labs became overrun with requests, forcing many vintners to make decisions in the dark, without having their fruit analyzed.
Looking for results
For grape growing, the Oakville vineyard is valuable real estate, situated in the highly esteemed To Kalon area, with the Mayacamas Mountains as its backdrop.
The To Kalon is arguably California’s most important grape-growing land. Some even call it Napa’s “first growth” vineyards, highly prized vineyards that are seen as first-class, rivaling the most valued growing areas in France. The neighbor of the UC Davis vineyard is Opus One Winery, known for its highly touted Bordeaux red blend which sells for nearly $400 a bottle.
Oberholster is joined in the vineyard by several other UC Davis professionals working on an assortment of experiments and primarily studying climate change. Most are endeavoring to find ways to protect vines from rising temperatures.
Shade cloths cover some vines, while plastic shelters others. And there’s a range of trellis structures varying in height and orientation, that support growing vines.
Oberholster, clad in a black jacket, black jeans and dusty black boots, pointed to a sensor attached to a trellis post near a vine. With an array of electronic devices on it spanning approximately 3 feet, the sensor can track volatile phenols (compounds in smoke) for a 1-mile radius.
Smoke taint can happen when grapes absorb volatile phenols in smoke, imparting undesirable aromas and flavors in wine. Some wine experts use the descriptor “wet ash” to describe smoke taint.
There are 13 sensors scattered throughout Sonoma County and Napa Valley and dozens more operating in Washington state and Oregon in collaboration with researchers there. There is eagerness for answers.
“People keep asking me, ‘What are the results? What are the findings?’” Oberholster said. “We don’t have results yet.”
Oberholster said the network of sensors is key. Over time, it will make it much easier to assess risk from smoke exposure so vintners can make informed decisions. And at low levels of smoke impact, there will be steps people can take in the winery and in the vineyard to reduce the risk of smoke taint.
“That’s a given,” Oberholster said. “We’re working on it. But I don’t think a magic bullet exists. If you’re going to be surrounded by a fire, I don’t think we’ll be able to do something to completely reverse it. I don’t want to set expectations that high.”
Grapes rejected in 2020
With more information, Oberholster is determined to protect vintners from the chaos they experienced in 2020.
Sangiacomo Family Wines, based in Sonoma, began the 2020 harvest with 5,300 tons of grapes on the vine. At the onset of the LNU Lightning Complex fires, they still had 4,300 tons yet to pick.
“Our nerves have been tested through decades of harvests, but 2020 stretched the limits,” said Steve Sangiacomo, a third-generation partner in his family’s business. “We have dealt with difficult harvests, but the smoke issue was something that really left us defenseless.”