Where there’s fire, there’s smoke. More than 100 wildfires are burning in 12 Western states this week, creating unhealthy air quality in many regions and causing new complications during the crucial harvest period in the country’s most prestigious wine appellations. With the sky—and vineyards—blanketed with smoke in many places, winemakers are anxious about the possibility of smoke-tainted wines.

In Oregon, the flames are still raging, with towns evacuated in Rogue Valley and smoke hanging over Willamette Valley. To the south, it has been nearly a month since lightning strikes ignited massive wildfires in California that threatened wineries and vineyards in Napa, Sonoma, Monterey and Santa Cruz counties. Firefighters continue to battle pockets of the LNU and CZU Lightning Complex fires but have mostly contained the blazes. By Labor Day weekend, vintners were busy harvesting their grapes and tasting rooms reopened.

What will weeks of smoke do to the 2020 vintage?

As the name implies, smoke taint can impart smoky flavors and aromas to a wine that render it unpleasant and unmarketable. Wines impacted by smoke taint are not harmful to drink, but they’re not pleasant. At high levels, the taste has been variously described as campfire, ashtray and char.

Prudy Foxx of consulting firm Foxx Viticulture in the Santa Cruz Mountains has dealt with smoke taint before. She said that if a grape cluster is heavily impacted, “it smells like the bottom of a wood stove.”

Wineries with vineyards that were near the fires are carefully monitoring their crop this year. Most producers won’t release a wine if it shows any signs of smoke taint exposure. But the loss of those grapes and wines could have a financial and human impact on wineries already reeling from the COVID-19 pandemic. And the fire season is not over yet.

“Everyone is concerned about the smoke and the potential of smoke taint,” said John Bucher of Bucher Wines in Russian River Valley. But Bucher and others caution that it’s far too early to tell what kind of impact the smoke might have on the vintage. Many wineries had started harvest when the fires arrived, and vintners are still collecting information as they pick their grapes. “No one is writing off the 2020 vintage,” he said.

How does smoke impact wine?

Smoke taint has become a growing concern for winemakers across the globe as climate change increases the threat of wildfires. In late 2019 and early 2020, bushfires burned along Australia’s southeastern coast for more than five months. Some vintners in the Hunter Valley reported that the majority of their grapes were unpickable due to high smoke taint levels. Chile suffered some of its worst wildfires ever in 2017, with flames damaging more than 100 vineyards.

California’s wine regions have faced wildfires on occasion, but since 2015 that has increased to nearly every year as the climate warms and the state endures repeated drought conditions. Fire is part of California’s ecosystem, but the season is starting earlier and ending later each year.

Studies have shown that grapes are typically more susceptible to smoke taint between veraison (the onset of ripening) and harvest, which started in early August this year. This year’s fires struck during that crucial period for many vineyards.

Smoke taint occurs when grapes are exposed to smoke, but the process is complex. Wildfires cause burning wood to release aromatic compounds called volatile phenols, such as guiacol and 4-methylguaiacol. The compounds can permeate the waxy cuticle of the grape skins and bond with the sugars inside, forming molecules called glycosides.

The process can render the phenols nonvolatile, meaning vintners cannot detect them by taste or smell. But when the grapes are fermented, the wine’s acidity begins to break down the bonds. The phenols become volatile again, releasing the smoky notes. This can continue to occur in the barrel or in the bottle. There are also indications that smoke taint may remain hidden until enzymes in the mouth break down any remaining glycosides, releasing the compounds as the wine is consumed.

Orange sky in San Francisco

The sky was orange over San Francisco Bay Sept. 9, as wildfire smoke combined with the marine layer. (Philip Pacheco/Getty Images)

But smoke taint is still difficult to predict and research has found no direct relationship between visual smoke—the particulate matter floating in the air—and the potential for smoke-tainted grapes. Volatile phenols are invisible to the naked eye. “There is no black or white here,” said Garrett Buckland, cofounder of vineyard consulting company Premiere Viticulture in Napa. “When it comes to smoke-related problems there is as much we know about it as there is that we don’t know about it.”

Researchers believe that the density of the smoke and the duration are key in assessing smoke taint risk. “If you are close to the fire but the smoke is blown away from you quickly, the risk of smoke taint is less,” said professor Kerry Wilkinson, a leading researcher in smoke taint at the University of Adelaide in Australia. “Whereas you could be farther away from the fire, but if the smoke drifts in and lingers in your vineyard, then the risk will increase.”

Anita Oberholster, cooperative extension specialist in enology at the University of California at Davis, believes that fresh smoke is more likely to cause smoke taint than older smoke since the volatile phenols have a half-life. “If that smoke directly hits you in 24 hours, it’s a risk,” she said. She points to a fire in Australia’s McLaren Vale where winds blew the smoke over the ocean before pushing it back over a vineyard. The grower thought that the whole crop would be ruined, but the smoke had no impact on the wines.

Are there possible solutions?

Vintners can try to mitigate unwanted flavors in their wines by minimizing contact with grape skins, since that’s where the compounds are concentrated. That means white wines are less likely to exhibit smoke taint than red wines, since most whites are fermented without the grape skins.

Winemakers can also attempt to extract the smoke taint with activated charcoal or spinning-cone technology. “Activated charcoal is the best fining agent that we have found so far,” said Oberholster. But she notes that the fining process, which adds the charcoal to the wine to bind with particles to make them easier to remove, can strip some of the wine’s flavors as well.

Smoke shouldn’t impact wines that are already fermenting in tanks and barrels. The fermentation process creates a barrier of carbon dioxide that should protect the wines, even those fermenting in open-top containers.

New research could help vintners in the fight against smoke taint. Researchers at Canada’s University of British Columbia in Kelowna are testing a spray used on cherries that could block the troublesome compounds from penetrating grape skins. In Napa, Buckland is experimenting with an agricultural spray that is being evaluated for public release as a crop protection product. The plant-derived product creates a waxy layer over the surface of the berries that limits gas exchange across the surface, minimizing the uptake of smoke-derived compounds. He sprayed it on some of his vineyards during the fires but says it’s too early to tell if it worked.

What about the 2020 harvest?

The next steps for winemakers will be to assess the smoke levels in wine regions impacted by the fires. “Until we know how widespread it is or it isn’t, there is no way to accurately know how to deal with it,” said Jake Bilbro, owner of Limerick Lane, near Healdsburg in Sonoma. “After we have the basic information of where we are, the next step is how to address it.”

Wineries in Northern and Central California are sending samples of their grapes and juice to private laboratories to be analyzed for smoke taint compounds. “We are testing every vineyard by doing mostly micro-fermentations and, so far, we have not had to reject any fruit yet,” said Kim Stare Wallace, president of Dry Creek Vineyard in the Dry Creek Valley AVA.

Labs such as ETS Laboratories in St. Helena can test grapes and juice for the primary volatile compounds found in smoke using different types of gas chromatography-mass spectrometry instruments. But the labs are swamped with thousands of samples. ETS is running its instruments 24 hours a day and said on its website that it may take up to three weeks for vintners to receive the results of grape samples. That means vintners can’t wait on results before starting vinification.


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Foxx remains cautiously optimistic that the wildfire smoke won’t have a big impact on vineyards in the Santa Cruz Mountains, but is encouraging all of her clients to test their grapes. “So far all of the tests have come back negative, but we haven’t had a lot that have come back yet,” she said.

Bilbro believes it’s most important not to jump to conclusions while winemakers gather more information. “This is a play-by-play scenario,” he explained, noting that Sonoma is a large and complex region. “There are a lot of steps that need to be taken and a lot of decision to be made.”

Buckland, who works with 22 wineries, said that some vintners have received favorable lab results showing numbers below the threshold for smoke taint. He is receiving data from multiple sources including from fruit samples, finished wines and from micro-ferments. “We are getting a lot of great and encouraging data back for our wines that are finished,” he said.

Smoke over Napa

A blanket of smoke spreads across the sky over Hall winery in Napa. High-altitude smoke shouldn’t impact grapes. (Ray Chavez/MediaNews Group/East Bay Times via Getty Images)

But some wineries are reporting smoke damage. “We are optimistic that the majority of our vineyards throughout California will provide a high quality 2020 vintage, consistent with previous years,” a spokesman for E. & J. Gallo told Wine Spectator. Most of Gallo’s vineyards have not been directly impacted, but there are some that experienced significant smoke exposure based on their proximity to the fires and the prevailing winds. “As a result, we will have portions of vineyards which will not be harvested in 2020, and in some cases, we may not bottle a 2020 vintage for select single-vineyard wines.”

One veteran vintner told Wine Spectator he’s making almost no Santa Lucia Highlands wine for his label this year.

St. Supéry CEO Emma Swain said that they won’t be harvesting their red grapes, Sémillon or Moscato from the Dollarhide Vineyard in Napa’s Pope Valley, near the Hennessey fire. “We are committed to producing only the very finest wines, and our analysis has shown us that the proximity to fresh smoke has damaged the harvest at the Dollarhide Vineyard for these wines,” said Swain. The good news is that the winery has seen no signs of damage at its vineyard in Rutherford.

The increasing cost of wildfires

The wildfires and smoke are impacting wineries’ bottom lines too. Some winemakers are reporting that insurance prices are rising and that some insurers are including exemptions for smoke taint in their policies.

“You have to have insurance on your properties, your buildings, your bulk wines and your case goods,” said Clay Shannon of Shannon Ridge in Lake County. In recent years he has seen a huge increase in insurance costs for bulk wine and case goods. “It’s hard to plan for it,” he said.

Crop insurance can help growers and wineries reduce their losses, but not everyone can afford it. Shannon has increased his crop insurance in recent years but he says It won’t pay the bills if he loses his grapes. “If you don’t have wine, you are out of the wine business.”

Foxx notes that some insurance companies are allowing vintners to go ahead and pick their grapes as long as they send them in for testing. “In general, and that’s a big general, the insurance companies are having to adapt their policies because of this unusual event,” she said.

Growers are also concerned that wineries may renege on their grape contracts. The California Association of Wine Grape Growers (CAWG) is reporting that numerous growers have said that wineries will not accept grapes under contract until lab results indicate that the grapes are not affected by the smoke. In a statement, president John Aguirre said that delays in testing, as well as wineries’ demands for test results, could mean growers will face both crop and economic losses.

“Our teams collectively remain focused on quality, and we are working with our growers to honor our grape contracts,” said Gallo’s spokesman, emphasizing the company’s commitment to its growers. “The unfortunate circumstances may require us to reject some fruit deliveries with high levels of detectable smoke taint.”

While it’s too early to make any assumptions about the 2020 vintage, many vintners are upbeat about the quality of the grapes they have harvested so far. Bucher is pleased with his Pinot Noir, though he does note that yields were down this year. “I think there are going to be some great wines that come out of the 2020 vintage,” he said.

And vintners all insist that wine lovers should not be concerned about purchasing smoke-tainted wines. Some wines simply won’t be produced in 2020. “Our reputations are at stake,” said Bucher. “There is absolutely no way that we are going to put wine in a bottle that is defective.”

U.C. Davis’ Oberholster echoed that. “I want people to believe and trust that if they see a wine on the shelf, that wine has not been impacted.”