Wine myths
American vines are immune to phylloxera
“American grapevines are immune to phylloxera, which is why we graft onto them.”
They are tolerant, not immune. American species evolved alongside the insect and survive its feeding on their roots; European vines do not. The insect still lives on them.
The full answer
Phylloxera is native to eastern North America, and the American Vitis species there evolved with it. Their roots respond to feeding by forming a protective layer that limits damage and blocks secondary infection.
Vitis vinifera has no such response. Feeding wounds on its roots do not seal, secondary fungal and bacterial infection follows, and the vine dies.
The distinction matters practically, not just semantically. Rootstocks vary considerably in how much resistance they offer, and some widely planted stocks have proved less durable than expected — most notoriously AXR1 in California, whose failure required the replanting of much of Napa and Sonoma from the 1980s.
The word to use is tolerance, or resistance, and never immunity.
Grafting onto American rootstock genuinely did save European viticulture, and it remains the answer.
A biochemical or physical process that has been demonstrated experimentally and is not seriously contested — the sort of statement that appears in enology textbooks without hedging.
What would settle it: A controlled experiment failing to reproduce the process.
In the timeline
Sources
Sources consulted
- Scholarship on the phylloxera epidemic and grafting — Academic history of agriculture
- UC Davis Department of Viticulture and Enology — University of California, Davis
- INRAE — French National Research Institute for Agriculture, Food and Environment — INRAE