Phylloxera in the Napa Valley in the 1990s

Phylloxera is a tiny bug endemic in the eastern part of the United States. Nevertheless, native American vines are resistant to this disease. During the 1880s, Phylloxera struck California, a region where European vineyards had been planted. By the 1900s, it wiped off 20,000 acres of land in the Napa Valley alone.

In 1992, the landscape of Napa Valley was marred by a dismal appearance due to the enormous impact of Phylloxera in the region. Consequently, the mounds of dead vines had been plucked from the ground and burnt in what had remained some of the most magnificent vineyards in the world.

The thick blanket of dark smoke manifested the gloomy disposition of the vintners, who woefully watched while fire ferociously consumed their labor of love. Phylloxera, the dreaded parasite that previously devastated the vines of Europe and California a century ago, had returned. Although researchers spent the previous century exploring a solution to this enormous problem, they could do very little about it.

The bug destroyed around 50,000 acres, almost half of the entire vineyard region, in Napa County and the neighboring wine areas of Northern California.

Currently, the Phylloxera outbreak has already reached its peak and has now ended. However, the bug shows up sporadically, and the old vines must continue to be destroyed. Many new plants are all over the place, and the quality of these newly-harvested grapes is higher than ever. Consequently, it leads the majority of California winemakers to believe that the state’s wines will also be of a higher quality.

Napa Valley

Fig 1. A vintner is looking for Phylloxera on Concord grapevine roots.

Several research studies suggest that grape plants be replanted every 30 to 35 years since they gradually lose their ability to resist disease over time. The vast majority of Napa Valley and Sonoma County vines were planted in the 1990s and were not slated to be replaced until 2000 or 2010.

However, many of the plantings established in the 1970s were incorrect grapes planted in inappropriate locations. According to Australian winemaker James Halliday, Phylloxera provided a chance to make amends for the legacy of the 1970s that would not have been possible under any other circumstances.

The only method to successfully combat the pest is to graft European vines onto the roots of their American counterparts. In the 1960s, agricultural specialists at the University of California recommended a rootstock called AxR1. It was supposedly resistant to Phylloxera and produced an abundant number of grapes.

This recommendation was made before Phylloxera became a significant threat to the vineyards in this region. As a result, most producers in California swiftly switched to AxR1 from St. George, a native American rootstock with a lower yield and weaker resistance against pests. A vast majority of California’s new wineries planted it throughout the decade of the 1990s.

Phylloxera on leaf

Nevertheless, vines growing on AxR1 roots in Napa Valley began to exhibit signs of illness after a few years. In 1983, scientists discovered that Phylloxera was the cause of the problem. Hence, the Northern California wine business invested more than half a billion dollars over the next decade in replanting vines. It is estimated that the Robert Mondavi Winery spent fifty million dollars redeveloping its Phylloxera-affected vines since the 1990s.

However, the wineries eventually benefitted from the catastrophe. They fixed their errors by relying on research about new grape clones, planting density, and the compatibility between rootstocks and vines. They learned about types of trellises for growing vines and how to position them for optimal light and water.

Compared to their yields two decades prior, there are now hundreds—even thousands—of more vines planted in each acre. These vines aim to produce grapes focused in taste and intensity by making the plants fight for sunlight, water, and nutrients.

One reason for the prevalence of Phylloxera and less productivity of new vine varieties is that plantation owners tried to accomplish too much in little time. Some of these novel rootstocks have exhibited evidence of previously unknown viruses.

Napa Valley

Fig 3. Graph showing the number of acres removed to plant AxR1 in Napa Valley and Sonoma.

However, most farmers and winemakers who could afford the transformation have been delighted with the new rootstocks. For instance, a 1997 Robert Mondavi Cabernet Sauvignon is one of the rare wines produced totally from post-Phylloxera grapes.

Most winemakers, like Mr. Winiarski, use post-Phylloxera fruit and grapes from vineyards in the production of their wines. Likewise, Cabernet from Beringer Vineyards between 1994 and 1995 were developed partly from post-Phylloxera grapes. They proved to be excellent examples of the winery’s Knights Valley Cabernets.

Although both wines were excellent, 1995 had a distinct flavor profile due to the addition of fresh grapes. The Beringer winemaker, Ed Sbragia, identified a unique sparkle (or brightness) in the 1995 vintage compared to the past vintages.

Read also: Napa Valley Wine History Timeline

This Day in Wine History

May 3, 1983: Scientists discovered that AxR1 roots used as a solution to the Phylloxera had weakened, and the Phylloxera had become resistant.

August 14, 1983: The Robert Mondavi Winery, which launched its trials with various new rootstocks, spent $50 million redeveloping its Phylloxera-affected vines.

November 17, 1992: The first vintage of Screaming Eagle was publicly available on this day. It became the most sought-after and pricey wine in all of Napa Valley. That year, a bottle of Screaming Eagle wine cost $75; its current price is nearly $7,000 per bottle.

April 23, 1997: Cabernet Sauvignon was produced from the post-Phylloxera grapes. This historic vintage produced robust wines that glorified the new Napa Valley Cabernet Sauvignon style. The entire harvest received the highest ratings ever recorded for a year in Napa Valley’s history. It served as a benchmark for the subsequent decade of wine production.


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