The Virus We Planted
Napa Valley's Next Phylloxera Crisis?

Ted Hall, Sep 27, 2026

I have walked vineyard rows in October for the better part of thirty-five years, reading the turn of the leaves the way every grower does: for color, for stress, for trouble. I could not tell you with certainty whether grapevine red blotch virus, a viral infection that quietly keeps an otherwise healthy-looking vine from ripening its fruit, is in a vineyard right now. That is not a comfortable thing for a grower to admit.

And not every red leaf means red blotch. Leafroll, nutrient deficiencies, trunk or root damage, and other stresses can produce similar symptoms.
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Red blotch can sit in a vine for two or three seasons before a single leaf shows reddish to reddish-purple blotches and the telltale redness in its veins, which means the honest answer for most growers in this valley is less a confident no than an unconfirmed not yet. Nobody would know without testing for it, and until recently, almost nobody did.

First recognized in Napa Valley in 2008, red blotch has since been confirmed in vineyards across the United States and internationally. Brix measures the sugar building up in a grape as it ripens, and the virus can cut that number by five or six degrees, while suppressing the anthocyanins that give red wine its color and altering the tannins and other phenolics that affect its structure. The mechanism is reasonably well understood: the virus disrupts the hormonal signals that trigger ripening, so the vine never receives the full instruction to finish the job it started in the spring.

A National Academies review commissioned by the California Department of Food and Agriculture in 2025 described grapevine red blotch and its sister disease, leafroll, as threats to a wine and wine grape sector that contributes $73 billion a year to the state’s economy, made harder to manage by how long it takes winemaking itself to reveal the damage.

Agricultural economists have modeled the lifetime cost of a heavily infected vineyard running into the tens of thousands of dollars an acre. That number is large enough to ask, carefully, whether this is the most consequential vineyard health threat Napa Valley has faced since the phylloxera crisis of the 1980s and 1990s forced growers across Napa and Sonoma to replant most of their vineyards at enormous cost.

Marc Fuchs, the Cornell plant pathologist who has spent over a decade tracking a single Cabernet Franc vineyard in Rutherford, watched its infection rate climb from 3.9% in 2014 to 36.4% in 2023. That vineyard sits in Rutherford, widely described as the center of Napa’s outbreak; nobody has done the valley-wide survey that would show how far the pattern actually extends beyond it.

He originally suspected red blotch was moving in from a nearby riparian corridor, the strip of wild vegetation that lines a creek or stream, which would mean many separate introductions, each carrying its own distinct genetic signature. The genetic evidence did not support that theory: the virus in his vineyard was too uniform for that many independent arrivals.

What he found instead were two distinct epidemics running in the same vineyard at the same time: a slow, randomly scattered spread of about 1% a year in one section, and a fast, radiating spread of about 6% a year in another, a difference he traces to how densely the vector, the insect that carries the virus from vine to vine, had already established itself in each part of the vineyard block.

An educational overview from Napa Valley Grapegrowers

​On November 3, 2026, Napa County voters will decide on Measure B, the Napa County Wildfire Preparedness, Watershed Protection and Open Space Preservation Act of 2026. Wildfire, watershed health, and land use all affect farming here, so we've summarized what the measure does. This post is meant to help growers make an informed decision.
The basics

• What it is: A new half-cent (0.5%) sales tax that would apply across the county, including every city, the town, and unincorporated areas.
• How long it lasts: 18 years, from April 1, 2027 through March 31, 2045.
• Estimated revenue: Approximately $23 million a year. The measure itself states this figure is an estimate that will depend on actual sales.
• How it got on the ballot: Measure B began as a citizen initiative, sponsored by the Land Trust of Napa County and Napa Firewise. On June 16, 2026, the Board of Supervisors confirmed the initiative received sufficient signatures to be placed on the November ballot.
• What it takes to pass: A simple majority (50% plus one vote).

Where the money would go:
​Revenue would be split evenly between two groups:
50% to Napa County, for wildfire preparedness. The Board of Supervisors would distribute funds through competitive grants, mostly to qualifying Napa County nonprofits. Eligible uses include:

• Clearing brush and other fuel along roads and at locations identified by local fire departments
• Fuel breaks around communities where homes meet wildland
• Programs that share the cost of defensible space and home hardening in high fire-risk zones
• Forest health work and removal of invasive species
• Assisting with prescribed burns
• Support for Fire Safe Councils
• Protection of critical infrastructure
• Emergency signs and maps for first responders

50% to the Napa County Regional Park and Open Space District, for watershed protection and open space. This share would also go out as grants to qualifying nonprofits and public agencies. Eligible uses include:

• Restoring streamside habitat
• Erosion control
• Building and maintaining trails
• Buying land outright, or buying conservation easements (a legal agreement that limits future development of a property while the owner keeps it)

Provisions growers may want to review closely:

• Land purchases require a willing seller. Any land or easement bought with Measure B money must come from a willing seller, at a price based on a fair market appraisal.
• Agricultural land is named. One stated goal of the land preservation funds is to "support the continuation of agriculture by protecting key agricultural lands." The measure doesn't set specific rules for buying working farmland or vineyards, beyond the willing seller and appraisal requirements.
• Cost share for landowners. The wildfire funds can support cost-share programs for "qualifying landowners." The measure doesn't spell out who qualifies, so details would likely be set when the grant programs are created.
• Domestic and drinking water sources are named as priorities. The measure lists several watersheds as examples: Lake Hennessey, Milliken Reservoir, Kimball Reservoir, Bell Canyon Reservoir, Friesen Lakes and Rector Reservoir.
• Environmental review. Passing the measure isn't subject to the California Environmental Quality Act (CEQA, the state law requiring environmental review of projects), but individual projects it funds would require CEQA review if applicable.
• Business purchases. Like other local sales taxes, Measure B would apply to many business purchases, not only consumer ones. California gives some farm purchases, such as certain farm equipment and fuel, a partial exemption from sales tax. This exemption generally covers only the state's share of the tax, not local add-on taxes like this one. If you are uncertain how this measure would affect your farming operation, please check with your tax advisor or the California Department of Tax and Fee Administration (CDTFA).

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Oversight and accountability:

• Oversight committee. A nine-member citizens' committee would review how the money comes in and is spent. The Board of Supervisors would appoint three residents, three fire department representatives, and three Park and Open Space District representatives. Three county officials would also attend as non-voting members. The committee could review spending but wouldn't set priorities or direct county staff.
• Grant agreements. Every grant would need a written agreement covering the scope of work, performance measures, audit rights, and the ability to take funds back if the terms aren't met.
• Annual reporting. Each grant recipient would report every year, and the Auditor-Controller would include the results in the county's annual audits.
• Changes need voter approval. The tax rate, end date, 50/50 split, and core purposes can only be changed by a vote of the people. The Board could make technical changes, but only with a four-fifths vote.

Context and differing views:

• Earlier measures. Countywide sales tax measures for open space failed in 2016 and 2020, and a wildfire prevention sales tax failed in 2022. Those were placed on the ballot by the Board of Supervisors and needed a two-thirds vote. Because Measure B is a citizen initiative, it needs only a simple majority.
• Supporters include the Land Trust of Napa County, Napa Firewise and the Napa Valley Vintners. Supporters explain that state and federal grants come and go, and a dedicated local source would provide steady funding, making the county more competitive for outside grants. The campaign estimates that visitors would pay about 40% of the revenue. That figure comes from the campaign, not from an official county analysis.
• Opponents include the Napa County Taxpayers Association. Its representative stated that this is "not the time to ask for another tax hike" given current economic pressures.
• Effect on rates. According to local reporting, the sales tax in the City of Napa would rise to approximately 9.25% if the measure passes. Rates differ across the county, so please check the rate where you live and do business.

Questions to consider as you decide:

• How would the planned wildfire and watershed work affect the land around your vineyards and your water sources?
• Would your operation be likely to qualify for, or apply for, cost-share or grant programs?
• How much does your operation buy locally that would be subject to the tax?
• How do you weigh the proposed oversight and reporting against the goals the measure is trying to reach?

Read the official materials:
We encourage every grower to read the primary documents, including the arguments for and against and the rebuttals. Napa County Elections has them all on its Measure B page, and you can reach the office at 707-253-4321.

Napa Valley Grapegrowers does not endorse or oppose Measure B. This post is for educational purposes only and is not legal or tax advice

Napa Valley's vineyards are part of the landscape everyone here shares. You see them on the drive to work, from a trailhead, or out the window at dinner. But for many neighbors, what happens inside those rows stays a bit of a mystery: how growers decide when fruit is ready, what a harvest morning looks like, and why farming well matters for the whole region.
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At Napa Valley Grapegrowers (NVG), we believe that support for agriculture grows from understanding, and understanding grows from real conversations. So we don't wait for the community to come to us. We go to them.

Trust Is Built in Person
Good relationships between farmers and neighbors aren't built through brochures. They come from showing up again and again, answering honest questions, and being open about how the work gets done. When people can taste a grape picked that morning or hear a grower explain why skin texture matters, agriculture stops being abstract. It becomes something personal.

That's the idea behind our public programs: meet people where they are, share what we know, and invite them into the story of Napa Valley farming.

NVC Estate Winery Friday Tasting Series: Cabernet Sauvignon Grape Tasting
Friday, September 25 | 5:30 to 6:30 PM
Napa Valley College Wine Education Center (Wine Spectator Building 3200)

This hands-on evening follows Cabernet Sauvignon from the vineyard to the glass.

• Read the grape like a grower. NVG Executive Director Caleb Mosley leads a grape tasting and shows how skin texture, acidity, and color can reveal where fruit is in its ripening, and how growers use those cues in the field.
• Explore the science. Will Thomas of Integrated Phenolics covers emerging research on phenolics and tannins (the compounds that shape a wine's color, texture, and structure), plus an early look at how 2026 vintage phenolics are shaping up this harvest.
• Taste the difference. The evening closes with a side-by-side tasting of two wines that take different approaches to ripeness, showing how one variety can express itself in very different styles.

Register here

NVG at the Napa Farmers Market
Saturday, September 26 | 8:00 AM to 12:00 PM
Napa Farmers Market, 1100 West Street, Napa
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Stop by our booth for a relaxed, family-friendly morning celebrating harvest. We'll have samples of freshly picked grapes from local vineyards, and our team will be on hand to answer your questions and share what harvest really looks like from the ground up. No experience needed, just curiosity.
Event details

Why It Matters
Every conversation at a farmers market table or in a tasting room helps build a community that understands and values local agriculture. That understanding matters. It shapes how our region thinks about land use, water, and the future of farming here. It connects people to the growers who care for Napa Valley's land. It also helps make sure grape growing stays viable and resilient for generations to come.
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Our mission is to cultivate viticultural excellence and environmental stewardship for Napa Valley. We can't do that alone. It takes a community that feels connected to the land and the people who farm it.

Come Say Hello
Whether you've worked harvest for decades or have never tasted a wine grape straight off the vine, you're welcome. Join us Friday evening for a closer look at the science of ripeness, or stop by Saturday morning for a taste of harvest. We hope to see you there.

Napa Valley Grapegrowers exists to serve the people who grow and steward this valley's vines, and we can't do that well without knowing what's actually on your mind. That's why we're launching our Member & Industry Survey this September, and why we're opening it up beyond our membership to the whole Napa Valley wine industry.

​Growers, vineyard managers, winery teams, suppliers, and consultants are all navigating the same pressures right now: water and regulatory questions, labor, market conditions, wildfire risk, and the ongoing question of what the next generation of this industry looks like. We want to understand how those challenges are landing across the board, not just within our own membership, and we want that to shape how NVG prioritizes its work.

This survey will also help inform how we bring the Patrick Foley Center, our new home in Oakville, to life. What programming would actually bring you there? What formats are worth our time and yours? Your answers help us build something the whole industry will use, not just something we assume the industry wants.

This one's simple: everyone.
Whether you've been an NVG member for years, you're not sure if you're a member, or you've never joined at all, your perspective matters here.

• Growers of any acreage, from a few vines to a few hundred acres
• Vineyard management companies
• Wineries with estate vineyards
• Industry trade partners, suppliers, and consultants
• Anyone who is hands on in the vineyards 

​If you're not an NVG member, we especially want to hear from you. Understanding whether and how NVG matters to people outside our membership is one of the most important things this survey can tell us.

​If you know someone in the industry who isn't an NVG member, forward this along. The more voices we hear from, the more useful this becomes for everyone who grows, works, and builds a life in Napa Valley agriculture.

In this episode of Grown in Napa Valley, host Caleb Mosley sits down with Dr. Monica Cooper and Dr. Malcolm Hobbs of the UC Cooperative Extension Napa County office for a wide-ranging conversation about how science gets translated into action in the vineyard. Monica, who has served as Napa's viticulture advisor since 2009, traces her research path from biocontrol and insect vectors of leafroll disease through to red blotch, which has become one of her primary focuses. Malcolm, who got his start counting ants in the vineyard part time, brings a social science lens to a field that doesn't always think in those terms. Together, they unpack a deceptively hard problem: how do you get neighboring growers to coordinate on a disease like red blotch, when that means having a sensitive conversation with someone you may have never met, or may have had a disagreement with in the past?

That question led Monica and Malcolm to study communication networks across the county and to explore the concept of neighborhood groups, voluntary, small-scale organizations where growers in close proximity can build the trust needed to actually work together on regional disease management. They talk through what makes those groups work, what gets in the way, and why spreading a new farming practice through a community looks a lot like any other kind of social change.
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For Glass with a Grower, Scott Becker of Realm Cellars arrives with two bottles that tell fifty years of Napa history in a single sitting: the newly released 2024 Moon Racer from the Stags Leap District, and a 1974 Cakebread Cellars Cabernet, the winery's first-ever Cabernet bottling, sourced from the same district and pulled from a Silicon Valley cellar where it had been stored impeccably for decades. The conversation moves fluidly between the wines, touching on mentorship, the pioneering names of Napa's early era, and Realm's philosophy of stewarding vineyard legacies — keeping the names, the histories, and the intention of the people who came before. 

• "How do you approach your neighbor to collaborate and coordinate practices? How do you have that conversation? That's very sensitive." - Dr. Monica Cooper
  
• "If you're making wine in Napa Valley today, you're standing on the shoulders of somebody else." - Scott Becker
  
• "How do I empower information to really move through our community? It doesn't have to come from me directly. In fact, if it doesn't come from me directly, that's more efficient overall." - Dr. Malcolm Hobbs
  
• "That name is now bigger than them. It's bigger than me. And so our job is to sort of steward that." - Scott Becker 
• "You wouldn't not manage for powdery mildew, because it's the norm of farming. What we need to do is get red blotch to that same place, normal farming." - Dr. Monica Cooper