Is Pierce's Disease the New Phylloxera?

10 min · 19. juni 2026

Beskrivelse

What I want to say in this piece is urgent. It’s urgent because of the recent discovery of sharpshooters on grapevines at several Costco locations in Northern California, where most of California wine is grow. It’s also urgent because Pierce’s Disease is a very serious plant disease that affects grapevines, perhaps as serious as Phylloxera, and I’ll get more into that. And it’s also urgent because the response to this situation is already proving to be as short-sighted and destructive as the disease itself. I have been talking about the urgent need to prepare for the spread of Pierce’s Disease for some time now. I recorded a conversation with Adam Tolmach of The Ojai Vineyard [https://beyondorganicwine.substack.com/p/hybrid-grapes-in-california-the-future-777?utm_source=publication-search], in which Pierce’s Disease is the main subject. And I wrote about Pierce’s Disease in my book, Wine Liberated [https://bookshop.org/a/124372/9781645024477]. When I wrote about it, now almost a year ago, I had no idea it would be so timely. But I can’t wait for the book to come out, so I’m doing this and other presentations as resources for California winegrowers, and soon winegrowers from other areas as well. Pierce’s Disease has made it to Europe. What I hope comes of this is that we reach out to the same politicians, Adam Schiff and Alex Padilla, who are asking for millions of dollars to “contain and eradicate” sharpshooters, and propose some long-term solutions that are actual solutions instead of just temporarily throwing money at something to assuage constituents yet accomplish little other than further ecological destruction. First, Is Pierce’s Disease the New Phylloxera? In some ways, no, but in some very serious ways, yes, it is. While Phylloxera is a root louse, Pierce’s Disease or Xylella fastidiosa, which I will refer to as PD for the most of rest of this piece, is a bacterial infection that can infect many plants including grapevines. PD is transmitted by insects to plants, and then the bacteria does the damage that causes vine death, while the actual phylloxera bug is the cause of vine death because it eats vine roots. But both can result in vine death. I say “can” because just like with phylloxera, Vitis vinifera has zero adaptation to resist or tolerate Pierce’s Disease. Vitis vinifera, of course, is the species of grapevine that accounts for most of the wine grown in California. The reason it has no adaptation to resist either PD or phylloxera is because it’s not from here where PD and phylloxera evolved. The majority of our wine grapes were brought over from Europe and are highly susceptible to the many insects, disease, and fungi that evolved on North America. However, there are several species of grapevines from California and the Southern United States and Mexico that have evolved adaptation to resist and tolerate Pierce’s Disease. Vitis Arizonica, Vitis Girdiana, Vitis Candicans aka Mustangensis, Vitis Cinerea, and Vitis Rotondifolia aka Muscadina, Vitis Cordifolia, and Vitis Monticola are among the species that have some degree of Pierce’s Disease tolerance or resistance. And all of these species have this PD resistance because sharpshooters and Pierce’s Disease are as endemic to this continent as are these grapevine species. So I want to first point out that the problem is not, as I’m hearing in the press, that sharpshooters are an “invasive pest” issue. Yes, glassy-winged sharpshooters came from the Southeastern US and are not native to California, but California has at least two other native species of sharpshooters that transmit PD – the bluegreen sharpshooter and the redheaded sharpshooter. These are not invasive, and our native species are not wine’s problem. The issue is that we have a wine industry built on vines without the genetic preparation for our normal, local native fauna. This is a really important and urgent point to get across to our politicians. Because the way a large percentage of those millions of your tax dollars are going to be spent is to remove insect habitat, that is to kill plants, with herbicides and to kill insects with insecticides. These are the main approaches to deterring and eradicating the “threat” of the existence of an insect that has been part of the California community since before Europeans got here, in order to protect our winecrops that we brought in from another continent and planted on hundreds of thousands of acres that happened to be sharpshooter territory. Let me be plain: There is no way to actually control and eradicate sharpshooters, except in a very localized and short-term perspective. And even if we could, it would be incredibly destructive to biodiversity and environmental and human health. Pierce’s Disease is not spreading because sharpshooters are “invasive.” It’s spreading because of climate change that we humans caused, and that is expanding the range that sharpshooters can occupy. And it’s spreading because of monocultures of plants like grapevines on which sharpshooters love to feed. And killing plants and removing biodiversity to destroy sharpshooter habitat and protect a maladapted monoculture is going to further accelerate climate change and increase the northward progression of sharpshooters, not stop them. Just ask the winegrowers in Texas and Georgia and North Carolina… they’ve been dealing with sharpshooters and highly prevalent Pierce’s Disease forever. In fact, we really should ask winegrowers in the Southeast and Texas about Pierce’s Disease… they have developed many resources and strategies for dealing with PD, and we don’t need to reinvent the wheel. I want to highlight two very important strategies that would be far more sane and ecological than trying to control and eradicate sharpshooters. First, Texas A&M developed an organic bacteriophage inoculation for vines that seems to be quite effective. The cost that I was able to find online was approximately $7 per vine per year, product and labor inclusive, for 2 annual injections. This is something that has been tested by Ridge at their Lytton Springs vineyard on Zinfandel. Other studies have found it to be highly effective on Cabernet Sauvignon, and decently effective on Chardonnay. It’s called XylPhi-PD [https://inphatec.com/wp-content/uploads/XylPhi-PD-Grower-PCA-Tech-Note-Final-02242023.pdf]. And as amazing as this product is, it’s not a long term solution. I don’t think it’s a great solution to create yet another input requirement for a maladapted grape. Do we really want to inoculate our vines twice a year for $7/vine. Inoculation is a stop gap measure while we transition to adapted grapevines. Yes, let’s give our tax dollars to this to avoid mass pesticide and herbicide use and environmental degradation. But let’s work toward the long term real solution of building a wine industry on resistance genetics. Which brings me to my second resource learned from the US South and Texas: We need to start using Pierce’s Disease resistant wine grapes. This is the other area toward which we should direct resources in several ways. We should financially incentivize Californians to rip out Vitis vinifera if they are going to replant with PD resistant varieties. But while this is a much better use of our tax dollars, there aren’t that many options for PD resistant wine grapes. UC Davis has bred and released 5 PD resistant varieties so far, and there are maybe another 5 that are popular for wine in the US South. There are hundreds of varieties of Muscadines, of course, and while I think there’s a lot of potential to modern Muscadine wines, especially among younger generations, they can be very different from vinifera and won’t be seen by most Pinot Noir growers, for example, as a viable substitute. So the other urgent need we have is for grape breeding. We need to financially incentivize it. And we need more than just one guy at UC Davis doing it. State funds should be given to California grape nurseries to bring in resistant grape species and varieties, and use CA nurseries as Davis extension sites for grape breeding. Breeding new varieties of delicious resistant grapes is the only real solution, and it’s a solution that gives us the potential for a more biodiverse, resilient, ecologically healthy future. California has been one of the easiest places to grow vinifera on earth for a while, but that has held us back from adapting. We have fallen behind even Europe, who are adopting and planting new resistant varieties more and more every year, ironically using North American genetics that we are neglecting. And this neglect has caught up to us. Wine won’t survive here by doubling down on the same varieties of grapes we’ve been growing. It is time for California to adapt. (Apologies for the reduced audio quality on this… I’m moving this week.) This is a public episode. If you'd like to discuss this with other subscribers or get access to bonus episodes, visit beyondorganicwine.substack.com/subscribe [https://beyondorganicwine.substack.com/subscribe?utm_medium=podcast&utm_campaign=CTA_2]

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