One balmy winter afternoon, Andy Beckstoffer, a grape grower who has done more than nearly anyone to shape the premium U.S. wine industry, was sitting in Mustard’s, a restaurant in Napa Valley that is a kind of clubhouse for the vintner class. Although Beckstoffer Vineyards, the largest private grower in California, had recently set a sales record with a blockbuster harvest of $55 million worth of cabernet sauvignon, its founder was not in the mood to celebrate. The wine industry was in trouble, facing its worst outlook in generations — and that was before the coronavirus struck.

The litany of plagues was merciless: too many grapes, thanks to an epic haul in California and Washington. Too many wildfires and weird bugs unleashed by climate change. Too many new wineries in Napa, upsetting the balance of agriculture and hospitality. And then there were the millennials, or millenniums, as the 80-year-old Mr. Beckstoffer likes to call them.

The generation born between 1981 and 1996 has been blamed for killing everything from napkins to homeownership, and thanks to its passion for hard seltzer, liquid marijuana and other drinkable novelties, it’s been cast as the murder hornet of the wine industry as well. Mr. Beckstoffer finds their health-crazed rituals (Drynuary?) puzzling.

“Wine is plant-based,” he said, shaking his head and picking mirthlessly at a spinach and mushroom burger. “Why don’t the millenniums drink it?”

A few weeks later, Mr. Beckstoffer’s anxiety was borne out by the publication of Silicon Valley Bank’s annual report on the U.S. wine industry — probably the most influential analysis of its kind. For years, its author, Rob McMillan, has preached about the alarming convergence of two trends: higher and higher bottle prices at the premium end of the market, and millennial indifference. Some farmers and winemakers have brushed Mr. McMillan off, and this time, he amped up the urgency, writing plainly: “The issue of greatest concern for the wine business today is the lack of participation in the premium wine category by the large millennial generation.”

The people who make wine don’t just age grape juice, they ripen customers, too, helping them evolve from undergraduate jug-swillers into middle-aged buyers of prestige labels. That process, Mr. McMillan says, appears to have stalled. Even as their purchases of other luxury goods have increased, millennials have balked at high-priced cabernets, which combined with the coronavirus makes 2020 “the worst time since Prohibition for fine wine producers in the United States,” he said in an interview.

The home of fine American wine is Napa Valley, where few benefit more from high prices than Mr. Beckstoffer. The region has unquestionably the best terroir in the United States, and within it, the choicest land has his name on a billboard next to it. Starting in the 1980s, Mr. Beckstoffer began seeking out what he calls “the good stuff” — the vineyards with records of success going back a century or longer. He now owns six, including To Kalon, a plot in the center of the valley considered the crown jewel of American viticulture. For the privilege of squeezing Beckstoffer grapes, winemakers behind labels like Stag’s Leap, Schrader and Realm pay up to $25,000 per ton — more than five times the Napa average.

All of which is to say: If the $71 billion California wine industry topples, then Mr. Beckstoffer, who values his empire at $500 million, may have the farthest to fall.

From Navy Grog to an American ‘First Growth’

Most Napa farmers hold some of their grapes back from market, in order to press them into wine themselves. Not Mr. Beckstoffer, who sells every last orb of fruit he can.

“Andy’s different — he has no interest in making wine,” said Curtis Strohl, the general manager of B Cellars, a Napa winery. In fact, Mr. Beckstoffer finds the vinifying process a bore, and he doesn’t care about drinking great vintages himself. His rivals in Napa say he cares only about money. Mr. Beckstoffer says he cares about farmers and the land. But it seems clear that over the course of his 50-year career, as the valley transformed from a drowsy agricultural community into an inland yacht club, the two motivations have worked in concert.

Mr. Beckstoffer — a courtly native of Richmond, Va., who pronounces vineyard “vin-yuhd” and “wine” as if it had three syllables — readily concedes that what brought him to Napa was the chance to make a killing. In 1967, recently graduated from Dartmouth’s Tuck School of Business, he was working for Heublein, an East Coast food and beverage conglomerate with products such as Smirnoff, Jose Cuervo and a pre-mixed tiki drink called Navy Grog.

The American palate was developing an appreciation for “quality wine.” That year, for the first time, more dry wine was sold than sweet. Mr. Beckstoffer helped Heublein acquire Inglenook, a cherished, family-owned winery that soon began pumping out “oceans of plonk,” as the novelist and wine critic Jay McInerney once wrote. Heublein also bought Beaulieu, where a similar transformation occurred.

“The arrogance,” Mr. Beckstoffer said. “We bought the two best wineries in the valley and screwed it up.” Though still in operation, neither has returned to glory. Looking back “makes your heart hurt,” he said.

Heublein’s bet swiftly turned sour. Spooked by labor issues, the company gave up on quality wine after a few years and started selling its Napa farmland — to Mr. Beckstoffer, who had resigned from the company and moved his family to the valley. By the 1980s, he had developed an ambitious agenda that would take decades to unfold.

Like Robert Mondavi and a few others, Mr. Beckstoffer came to believe that a once-in-a-lifetime opportunity lay dormant in Napa’s soil. For more than a century, the potential of the valley’s wine had been recognized even by Europeans. But the quality was uneven and financial acumen was lacking, and as Mr. Beckstoffer saw it, the chance to create an American equivalent of the First Growths of France was being squandered — like a great but unknown painter in need of a sharp-elbowed dealer.

“The farmers were good at farming, but bad businessmen,” Mr. Beckstoffer said. “You couldn’t make any money owning land and selling grapes.” He believed that the local wine would only reach its potential if it was strategically elevated into a luxury product — scarce, expensive, vigilantly branded — even if that meant leaving behind an Arcadian era centered on small family farms and affordability.

“In every agricultural area, there is a citizen hierarchy,” Mr. Beckstoffer said. “Here, winemakers are at the top, and farmers used to be at the bottom.” He once told an interviewer that his overriding goal was to give grape growers more clout.

With his Ivy League M.B.A. and corporate pedigree, Mr. Beckstoffer is not exactly a typical farmer. In the 1980s, when Napa was still oriented toward relatively humble varietals like zinfandel, an epidemic of phylloxera — a rapacious insect that feeds on the roots and leaves of grape vines — wiped out crops. Mr. Beckstoffer and others led the charge for a valley-wide replanting with the more glamorous cabernet, while introducing data analysis and other elements of industrial farming that magnified yields enormously.

He also wielded back-room political skills to outmaneuver opponents. Like any good luxury item, Napa land is in short supply — 300 square miles, most of it owned by a few families and corporations. The question of whether to farm it, preserve it or use it to attract tourists is never far from any conversation. In 1990, as wine drinkers were developing a voracious appetite for Napa cabs at seemingly any price, Mr. Beckstoffer was the driving force behind a landmark piece of legislation, the Winery Definition Ordinance, requiring any wine with the word “Napa” on it to be made from 75 percent local grapes.

The statute also limited what sort of social and commercial activities, such as weddings, could take place at wineries. A generation later, vintners still complain that the bill funneled business to its champion and crippled the rest of the valley.

As Mr. Beckstoffer became a land baron among land barons, he also regularly enraged the winemakers at the top of Napa society, whom he dismisses as “blenders” and “media stars.” One article from 1990 describes an incident at a country club, in which a winery owner realizes that she has been seated near him and asks to be moved. Another quotes a winemaker calling Mr. Beckstoffer “a real snake.”

Mr. Beckstoffer displays both articles on his website. “If you’re not making enemies,” he said, smiling innocently, “you’re just taking up space.”

For good measure, he has also stymied real estate developers. As one of the sightlier parts of Northern California, with its majestic oaks and gaudy colors, Napa has some of the highest real estate prices in America and some of its most expensive hotel rooms. But Mr. Beckstoffer has long sought to choke off the development of Napa as a “lifestyle resort.”

Chuck Wagner, the founder of Caymus Vineyards, a prominent Napa winery, is one of many proponents of building up the region — more wineries, more hotels, more tourists. “People want to experience the beauty of the valley,” he said. “Andy is against additional business.” He added, “A lot of people believe that Andy does things for personal financial gain.”

Mr. Beckstoffer insists he has higher principles, and despite his corporate sheen, when he talks about securing “agriculture in perpetuity” for Napa Valley, he has the unmistakable zeal of an ideological convert. The heritage vineyards he bought are now in trusts that cannot be developed or sold.

“You have to ask yourself, what do you want to leave for your children?” he told me. “Someday, some spouse of a grandchild of mine will want to build a hotel on one of our vineyards — and they will hate me, because they can’t.”

Strong-arm tactics — and customers happy to pay the price

The Dr. Crane Vineyard is not what you think of when imagining world-class terroir. Wedged between a ready-mix concrete plant and a grade school, it is nevertheless one of Napa’s oldest vineyards, originally planted in the 1850s by George Belden Crane, the first grower to transplant European viticulture to Napa. Ignore the immediate surroundings — the drooping electrical wires and paved yards — and at the end of a winter day, with a pink sun falling behind the Mayacamas Mountains in the background, the rows of trellised vines look as picturesque as any #winecountry social media post.

“Look at the uniformity of the rocks!” Mr. Beckstoffer said, cupping one the size of an apple. Beckstoffer grapes are renowned for their consistency, the result of exacting and technology-driven farming, including heavy use of fertilizers. But most of what makes the heritage vineyards superlative is a mystery. “People say it’s the soil, or the climate,” Mr. Beckstoffer likes to say. “The truth is, we don’t know.”

As he drove away, he gestured with the back of his hand at the valley’s suburban sprawl — light, by California standards. “There are very few places in the world where agriculture is the long-term, highest economic value, best use of the land,” he said. Napa used to have many vineyards as exceptional as Dr. Crane, he said, but now “they have a big house on top of them.” Asked how long he intends to own the property, he said, “Forever. Even if disease wipes it out, it will be a field.”

When he talks of Napa farming, Mr. Beckstoffer speaks loftily, invoking paragons of American culture like skyscrapers and jazz. “You have to have a larger cause, something bigger than money,” he said. “This place is a national treasure. Napa Valley put American food and wine on the map.”

Mr. Beckstoffer’s holdings here total only about 1,000 acres, or roughly 2 percent of the valley’s planted area. But thanks to his near-stranglehold on prime vineyards like To Kalon and Dr. Crane, he can demand almost whatever price he wants for his product. Decades ago, he settled on a formula borrowed from Burgundy: For a ton of grapes, he would charge 100 times the price of a bottle made with them. In other words, if a bottle made from cabernet sauvignon grown at Dr. Crane retails for $150, the cost of buying the fruit equals $15,000 per ton.

He also requires winemakers to put his name on their labels — in effect, making them do his marketing for him. Some find it coercive, but Mr. Beckstoffer compares the arrangement to the “Intel Inside” logo found on Windows PCs.

“He’s in a position where he can do that,” said Tor Kenward, a winemaker who makes cabernets with Beckstoffer grapes, retailing for $200 to $300. “Some winemakers are uncomfortable with the terms, but most think it’s worth the price.” At B Cellars, Mr. Strohl’s wine cave features a shrine-like Beckstoffer Heritage Room. “I’ll pay the price because I know I’ll get consistently excellent grapes, and I can make stellar wine,” he said.

The price of Napa bottles has risen year after year to ever-more incomprehensible heights — $1,000 for cult brands such as Screaming Eagle and Colgin — creating a seemingly invincible aura of prestige. As Mr. Beckstoffer likes to say: “You put ‘Napa Valley’ on a toothpaste, you can sell it as a luxury product.”

The question is whether the category will continue to thrive as its most lucrative demographic, the baby boomers, ages out of its prime consumption years and a new cohort takes their place — or doesn’t.

Plagues come, plagues go

Every year, Napa awaits the publication of Silicon Valley Bank’s “State of the U.S. Wine Industry” analysis. In an interview, Mr. McMillan said his increasingly vocal warnings of the millennial threat to the industry were finally being heard.

“Every piece of research shows they’re lagging,” he said. “It’s not that they don’t drink wine. There are just other choices. In the 1990s, there was incredible wage growth, but beer sucked. Now, guess what? Beer is good. And so are spirits.”

Mr. McMillan said he thought that in the short term, the coronavirus pandemic might benefit the premium wine industry, with data showing locked-down consumers “willing to spend up,” perhaps as they try to recreate the restaurant experience at home. But the larger picture is not encouraging. When national crises come, so does a sense that we are all going to be more serious, more responsible, and stop buying expensive bottles of cabernet. After Sept. 11, 2001, terrorist attacks and the 2008 financial crisis, the luxury wine market took painful hits. In such times, people don’t stop drinking; they just buy less of the expensive stuff.

When I caught up with Mr. Beckstoffer again in March, by phone, he was sequestered at home. The pandemic had, if anything, helped him come to terms with his basket of concerns, putting them in perspective.

I asked him to compare the crisis to earlier troubles in his career of half a century. In the 1970s, to buy Heublein’s land, he went into debt, then saw the price of grapes crash, causing him to default on loans and go into forfeiture. As he was beginning to recover, phylloxera hit and many wineries went under. He saw it as an opportunity. “When hard times hit, people sold,” he said. “That’s when we bought a lot of our vineyards.”

He seemed sanguine about the Covid-19 economic crash. “In this business, we tend to get seven or eight good years, then two or three bad ones,” he said. In the mind of a farmer, plagues come and go.

The millenniums, however, still haunted him. “Millennials,” he corrected himself.

“We’ll figure it out,” he continued. “A well-managed business will always weather the storm. Nobody in Napa Valley is panicking. No land that’s really good is for sale that I’ve seen. If something comes up, I’ll probably buy it.”