When Phylloxera Came Back: California’s AXR#1 Disaster

A century after phylloxera devastated Europe, it returned — in Napa Valley — and forced the replanting of the majority of Napa’s vineyards, and tens of thousands of acres across Napa and Sonoma, at a cost estimated above one billion dollars.

The second disaster was not caused by an unknown enemy. Phylloxera was thoroughly understood by the 1980s, and the cure — grafting onto resistant rootstock — had been standard for a century. California simply planted the wrong rootstock, one that had been abandoned in France eighty years earlier for exactly the reason it would fail again.

The rootstock that was too good to refuse

AXR#1 was bred in France in 1879 by Victor Ganzin, crossing the European variety Aramon (Vitis vinifera) with the American Vitis rupestris.¹² That vinifera parentage was its selling point: it gave AXR#1 exceptional vigour, easy propagation in the nursery, and excellent compatibility with grafted varieties. Growers loved it. In California’s fertile valley floors it produced generous, reliable crops.²³

The vinifera parentage was also the flaw. Phylloxera resistance comes from American Vitis species; breeding a European wine grape into a rootstock dilutes precisely the trait the rootstock exists to provide. Resistance is not binary — it is a spectrum — and AXR#1 sat lower on it than its popularity implied.³⁴

The warnings, ignored

France worked this out early. By the early 1900s AXR#1’s insufficient resistance and short productive life were recognised there and its use was abandoned; comparable failures were later reported from Italy and South Africa.² The evidence was neither obscure nor new.

Nonetheless, following Lloyd Lider’s 1958 study the University of California, Davis recommended AXR#1 for the coastal valleys, and the industry adopted it comprehensively — by the crisis an estimated 70% of vines across Napa and Sonoma were planted on it.¹³ The reasoning was that California’s phylloxera pressure differed from Europe’s and that field performance had been good for decades. It was, in effect, a bet that the local strain would stay mild.

Biotype B

The bet lost in the 1980s. A more aggressive strain of phylloxera — designated biotype B — proved able to attack AXR#1 far more effectively than the populations the rootstock had coexisted with. (Biotype B is a performance-based classification rather than a genetically defined lineage, and whether it arrived, was selected for, or derived from existing strains has never been settled.)²⁴ The first signs of decline appeared around 1982, and were widely met with denial: vines yellowing and dying in patches were blamed on almost anything else. The new strain was formally described in 1985, and once decline was visible infested vines typically failed within about three to five years.¹

UC Davis withdrew its recommendation in 1989.¹³ By then the damage was structural.

Replanting a valley

Estimates of the scale vary by source and by how the area is drawn. Napa held roughly 45,000 acres of vineyard at the time, and about two-thirds of its plantings were affected; across Napa and Sonoma together, figures from 40,000 to 70,000 acres are cited as needing replanting. Per-acre costs are put at roughly $25,000–$50,000 in 1990s dollars depending on the estimate, and the total is commonly quoted at more than one billion dollars — though published figures range far higher and no rigorous net-cost accounting was ever done.¹³ For growers it meant tearing out productive vines, forgoing several vintages of income, and carrying the cost of replanting before any return.

The unexpected silver lining

Because the valley had to start over, it started over better. Replanting was done on genuinely resistant rootstocks — the riparia, rupestris and berlandieri crosses discussed in our guide to rootstocks — and growers took the opportunity to correct decisions frozen in place for decades: tighter vine spacing, better-matched clones, improved trellising, and rootstock chosen for each block’s soil rather than by default.³⁴

The crisis also triggered serious research into how rootstock influences wine quality, not merely vine survival.² Many observers regard the replanted Napa of the late 1990s as better than the vineyard it replaced — an expensive way to modernise, but a real one. For the region’s longer arc, see Napa Valley wine history.

The lesson

Phylloxera has not been beaten; it has been managed, and management can lapse. The AXR#1 episode is the clearest modern proof that resistance is a spectrum rather than a switch, that a rootstock’s convenience can quietly outweigh its protection in planting decisions, and that field evidence from other continents deserves attention even when local performance looks fine. It is also why regions still free of the insect — South Australia, Western Australia, Tasmania, Chile — enforce quarantine with such seriousness.⁴

Read more

• Phylloxera: how one insect nearly ended wine — the original crisis
• Why almost every wine grape grows on American roots
• Napa Valley wine history
• All our phylloxera coverage

References

1. WineWiki, “Phylloxera and Napa Valley Replanting” (biotype B timeline, 1989 withdrawal, acreage and costs). ↩
2. wein.plus Lexicon, “AxR 1” (Ganzin 1879 breeding, Aramon × rupestris, French discontinuation c.1903). ↩
3. Wine Enthusiast, “Phylloxera in Napa Valley: Then and Now.” ↩
4. Phylloxera / Rootstock — vinifera-parentage rootstocks and resistance limitations; quarantine regimes (corroborated). ↩

Want to read more? Try these books

Phylloxera Christy Campbell

Judgment of Paris George M. Taber

Wine Grapes Robinson, Harding & Vouillamoz

As an Amazon Associate, This Day in Wine History earns from qualifying purchases. Some links on this page are affiliate links.