On the Many Frustrations of Gardening: Pierce’s Disease

Damn Pierce’s Disease!

I really wish that glossy gardening magazines would, every once in a while, devote some space to capturing some of the soul-crushing disappointments of tending plants. Can we please have a cover of Sunset Magazine featuring an aphid and slug infested cabbage? Frustrations are compounded when a beloved perennial plant you’ve been growing for years comes down with a fatal disease. Such was the case when my flame seedless grapevine, which was planted to cover our backyard arbor, contracted Pierce’s disease, caused by an incurable bacteria (Xylella fastidiosa) spread by an insect called the sharpshooter. Pierce’s was discovered in 1892 in Anaheim and is basically the reason we no longer have many vineyards in Southern California. Once a vine gets Pierce’s it will die within a few years. You have to admit failure and rip it out, which I plan to do soon.

“Wood on new canes matures irregularly, producing patches of green, surrounded by mature brown bark.”

To confirm that my vine had Pierce’s I called Jerry Turney, plant pathologist at the Los Angeles County Agricultural Commissioner’s Office. When I described the symptoms, Turney agreed that it sounded like Pierce’s. The signs of Pierce’s, as described in UC’s pest management guide, are:

“(1) leaves become slightly yellow or red along margins in white and red varieties, respectively, and eventually leaf margins dry or die in concentric zones; (2) fruit clusters shrivel or raisin; (3) dried leaves fall leaving the petiole (leaf stem) attached to the cane; and (4) wood on new canes matures irregularly, producing patches of green, surrounded by mature brown bark.”

“Fruit clusters shrivel or raisin.”

Turney described the life cycle of the sparpshooter, one of the main carriers of Pierce’s, who spread the diesase by feeding off the sap of infected plants. Sharpshooters live in riparian areas and when a stream goes dry they fly off in search of irrigated plants to feed on. Sharpshooters also like to spend the winter in citrus groves which, while not susceptible to Pierce’s, provide habitat. Our hot dry summers, which dry out local streams and rivers, and abundant citrus trees, make inland Southern California an especially bad place to try to grow grapes. Why nurseries continue to sell vines suseptable to Pierce’s here is a mystery to me.

In the 1990s Pierce’s disease wiped out 40% of the vines in Temecula’s vineyards. Northern California’s vineyards have experienced what Turney described as an “edge effect”, with Pierce’s claiming the vines on the outside of vineyards. The only way to prevent the spread of the sharpshooter is frequent application of pesticides (on both grapes and citrus), not practical for the home gardener and we’re organic around the Homegrown compound anyways. In fact, one of the pesticides used to control shapshooters is Imidacloprid, implicated by many in the recent disappearance of honey bees.

Pierce disease resistant Vitus californica attacking our house.

The only hope for long term control, as Turney sees it, is by breeding hybrid grape varieties resistant to Pierce’s. Turney strongly advised against trying to grow wine or table grapes in Southern California. After losing three table grape vines in ten years, I can attest to the wisdom of Turney’s advice. To grow grapes in the warm southern parts of the U.S., you simply have to plant Pierce resistant varieites such as the native Vitus californica or muscadine grapes. The contrast between our flame seedless and our Vitus californica vine, in fact, is stunning. The flame is stunted and diseased, while our Vitus californica is so vigorous that I have to beat it back on a daily basis to prevent it from subsuming our house and the neighbor’s.

And while we’re working on resistant grapes we may need to start hybridizing citrus as well. While the strain of Pierce’s that took down my grape vine is harmless to citrus, there is a variant of the bacteria that is currently ravaging the citrus of Brazil and Argentina which causes a disease called Citrus Variegated Chlorosis. It’s also fatal and has the potential to spread to North America via the shipment of infected trees. With a global economy and porous borders it’s bound to show up someday. Might as well get ready.

Gardening is a humbling lesson in evolutionary biology. It’s all about survival of the fittest. Work with evolution by selecting for immunity to pests and disease and you’ll harvest the rewards. Resistance is futile.

More info at piercesdisease.org.

If any of you readers know of a comprehensive list of resistant varieites for California please leave a link in the comments! So far I’ve been able to find lists for Florida and Texas.

Update 7/6/09: Reader Anduhrew sends an amazing link about a home remedy involving injecting antibiotics into an infected vine.

And here’s another article on possible cures.

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17 Comments

  1. I have had terrific luck with two Concord grape vines I planted over twenty years ago. Concords not supposed to do well in SoCal climate, but mine have thrived, despite erratic care.
    Sue at Camp Waterloo

  2. Is there a natural enemy to the sharpshooter and would hardening the plants early on with Neem or other supplements help? It’s a shame to see the old varieties vanish.

  3. Have you tried diatomaceous earth? Totally safe, can be ingested by humans even and kills bugs dead.

  4. yeah, let’s have that cover of Sunset magazine show peaches still green and on the tree, half eaten by squirrels (so that the peaches will rot before they mature).
    Anyone know good cures for squirrels in the city? (guns are out) If my elderly father-in-law can’t keep them out of a bird feeder at his place, I doubt I have any chance of keepign them out of the peaches.

  5. Sue–Turney actually suggested Concord as being resistant to Pierce’s. However, when I tried to verify this I found a study indicating that Concord is actually susceptible to the disease. I’m going to replant with something I know is resistant, i.e. muscadine or a native variety.

    Anonymous–yes the sharpshooter has predators, so that could theoretically be part of an integrated pest management approach. I don’t know if neem oil would work. You’d have to really be on top of spraying it if it did. It is true that young vines are more vulnerable. However, all it takes is one bite from a sharpshooter to transmit Pierce’s. I doubt diatomaceous earth would work, but I don’t know for sure.

    And Transition Westchester–no kidding about the squirrels. How about arrows? Just kidding. The only effective control in the city is to prune your trees to keep them small. Then throw bird netting over the whole tree during the fruiting season. I’ll do a post about this soon. This is what my friend Tara at Silver Lake farms does–works very well.

  6. That’s so sad! I just planted a couple of grape vines this year, so we’ll cross our fingers and hope they don’t get hit with this. Good to know for future planting, though.

  7. Timely post, sad news. Our vines are a disaster this year, from the combined effects of Pierce’s and a tenacious powdery mildew outbreak following persistent SoCal June gloom. Citrus is definitely the main host of the breeding sharpshooters in our neighborhood. Despite Turney’s admonition we’re going to keep trying; moving existing or planting new table and wine vines to the side of the house away from host plants. I haven’t seen a resistent list of vines for CA. Hybrid varieties are currently being tested, and I’ve read of vaccine and parasitic wasp deterrents as well.

    Re squirrels: my neighbor has had some luck with their rodent-hating pet dogs (terriers).

  8. Tetracyclin is a broadband antibiotic which I’d prefer not seen used in no-human use, let alone anti-biotic in food at all. While scientifically interesting, I can’t see this to be the solution for edible food.

  9. Anonymous,

    Yeah, the problem, I’m guessing, would be that the antibiotic treatment would need to be re-applied with each infection. Then we’re back to evolutionary biology 101–we’ll end up breeding antibiotic resistant Xylela fastidiosa and exposing people to yet more anti-biotics in food. Long term the answer is breeding resistant vines.

    Nevertheless, I have to admit that I’m tempted to try this treatment out of curiosity. I’ve got to rip the vine out anyways and I just happen to have some anti-biotics on hand. A bit of a Dr. Faustus moment, I admit.

  10. I want to try this out of curiosity too. but (un)fortunately i don’t have a grape vine with Pierce’s disease. Please let me know how it goes!

  11. p.s. you could always try some powdered olive leaf or olive leaf extract instead of tetracyclin. though I have no idea how much you’d use then.

  12. In answer to “Anyone know good cures for squirrels in the city?” Joy of Cooking used to have information about skinning and cooking them. Find a Joy of Cooking edition that was printed before the late 1990s. Are you a good shot?

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