The Mendocino Complex fires in Lake County created a dense plume of smoke over the Beckstoffer vineyard for several days in early August. More than 50 vineyard workers were sent home that week because of poor visibility.

“You could barely see because the air was so dense,” said vineyard manager Clint Nelson.

He oversees the Beckstoffer vines off Highway 29 in Kelseyville.

What does this dense plume –– this chokehold –– mean for the grapes this harvest? During the Northern California wildfires last October, most of the grapes in Sonoma and Napa counties already had been harvested. By comparison, harvest is still five to six weeks away for Mendocino and Lake counties.

UC Davis and the Australian Wine Research Institute agree that wine grapes are most susceptible to smoke taint from veraison to harvest.

Veraison, for the uninitiated, is the onset of ripening and it’s currently underway for most of Northern California’s vines. The French term, (pronounced ver-ray-shon) is defined by the change of color of the grape berries. It typically signals harvest is just about six weeks away.

The research on smoke taint has prompted Nelson and his team to plan a series of tests over the next few weeks to determine whether the Beckstoffer vineyard has been affected by it.

The company, Beckstoffer Vineyards. is one of the largest vineyard owners in Lake County, if not the largest, with 4,000 acres. The company has 1,350 acres planted to vines, with 95 percent cabernet sauvignon.

“I feel more work is needed in the field of smoke taint to better understand the variables that impact grapes’ susceptibility,” Nelson said. “We’re going to hand wash some of the fruit and machine wash some of the fruit and then compare those samples to grapes that aren’t treated.”

Meanwhile Vintner Christian Ahlmann of Six Sigma Ranch and Winery, about five miles southeast of Lower Lake, doesn’t plan to do any testing.

“We’re not worried because we’ve just been experiencing a haze,” he said. “In the past few years we haven’t had any problems.”

Ahlmann said the winery plans to put the grapes in the tank and if there’s a problem, it can filter out any smoke taint.

The 4,000-acre property is a cattle ranch coupled with a winery, and it has 40 acres of grape vines planted. The signature grape is Tempranillo, which originated in Spain. It also produces cabernet sauvignon and sauvignon blanc, along with a few miscellaneous varietals.

“In certain instances smoke can add a charming note,” Ahlmann said. “With our 2008 Tempranillo the smoke added depth and complexity. Tempranillo already has a spicy complexity and if it gets mild smoke taint, it just accentuates that.”

Ahlmann said despite the rash of fires, he’s taking everything in stride.

“The bad news is we can’t do anything about the fires, but that’s also the good news,” he said. “We play it out as it comes.”

Wine writer Peg Melnik can be reached at 707-521-5310 or peg.melnik@gmail.com.