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GL0910-tim-hearden-problems_BT_Edits.jpg Tim Hearden
The sun is shrouded in smoke in Northern California on Aug. 19.

Heat, smoke create problems for wine grape growers

Nearly 11,000 lightning strikes sparked hundreds of wildfires in August, including many in wine country.

At this point, California grape growers have started to wonder just how many horsemen actually come with the Apocalypse.

In addition to existing labor shortages compounded by the coronavirus pandemic, they’ve had to endure the usual regulatory and environmental problems further complicated by some samples of climate change in the form of excessive heat.

That heat got even hotter when unanticipated thunderstorms struck in late August and, according to Gov. Gavin Newsom, dropped down nearly 11,000 lightning strikes that subsequently sparked several hundred wildfires — some of the largest in the state’s history — many in wine country.

As Napa County temperatures approached triple digits and smoke and flames swirled about, California’s Department of Forestry and Fire Protection delivered more bad news: “Much of Northern California has received below-normal precipitation leading to drier fuels with lightning events possible into September and above-normal, large fire potential persisting through October.”

By most accounts, it’s been an historic heat wave bringing drought-related problems and air-quality issues that ultimately prompted the governor to proclaim a State of Emergency on Aug. 18. The Western Agricultural Processors Association noted: “Outdoor workers began monitoring the Air Quality Index as part of the Protection from Wildfire Smoke Regulation requiring respiratory protection.”

Tony Bugica, director of farming for Atlas Vineyard Management, which farms 3,500 acres in the North Coast, said “perfect storm” aptly described the challenges.

“2020 is like nothing we’ve ever been through,” Bugica told the San Francisco Chronicle.

Some local residents seem unfazed.

“It’s the new normal — what next?,” Napa clothing store manager Bulah Cartwright told the New York Times. “We’ve had earthquakes, fires, flooding. It’s exhausting, but we’ll get through. We’ve gotten through worse.”

It's not expected to get that much better in the immediate future as La Nina conditions (associated with warmer and drier) are expected going into the fall and winter with above-normal temperatures and below-normal precipitation.

All of which puts an earlier, mid-August grape crop estimate released by USDA and the National Agricultural Statistics Service, very much in question, if not in doubt. Predictions for grapes bode particularly well for California growers, the report stated.

Larger crop expected

Prior to the many catastrophes, USDA/NASS forecast this year’s grape production in America at 7.18 million tons with 4 million tons of wine grapes to be produced in California — 59% of the state’s total grape crop.

“Those numbers would mean a 4% increase over 2019 while table grape production at 1.35 million tons would represent a 14% jump and grape production for the raisin sector would weigh in at 1.4 million tons, an 8% bump from last year,” NASS said.

While crush numbers won’t be official until whatever kind of modified harvest is completed, the University of California, Davis Viticulture and Enology Department is offering a “Wildfire Impact on CA Grapes and Wine” posting about the resiliency of grapevines. “They don’t burn easily and in many cases, vineyards act like fire breaks and play a beneficial role,” the university said.  “Expectations are that grapevines will fully recover if they did not actually burn, although yield may be impacted by smoke taint (which does not carry over to the next season).”

Writer Caroline Firman said, “The risk of smoke taint increases with continual or repeated exposures of heavy fresh smoke so any exposure has the potential to be problematic. Because there is no direct relationship between visual smoke and potential risk of smoke-impacted grapes, we strongly advise growers and wineries to test their grapes for smoke exposure marker compounds (volatile phenols) that are not visible to the naked eye.”

The 2020 blazes are only the latest in a series of devastating fires that have hit the region in the last three years. In 2018, smoke from the Mendocino Complex Fires destroyed the market for an estimated $41 million in wine grapes grown in vineyards near burned areas.

Following a lengthy explanation of smoke taint science, the UC’s posting concludes: “It is important to note that the compounds responsible for smoke taint are naturally present in grapes at low levels, part of the pleasant aroma compounds released into wine during barrel aging, adding complexity to the wine. It is only at very high levels that it will be seen as a fault or taint.”

Seven northern California counties, including Napa; Sonoma; Santa Cruz and Lake, have been declared major disaster areas making them eligible for federal disaster relief funding.

For more news on pests, disease management and other issues affecting vineyards, subscribe to the bi-monthly newsletter The Grape Line.

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