Testing continues, but new treatment meets approval of U.S. EPA and several state regulators.
Walk around certain vineyards, whether the well-renowned regions of California or the less familiar in Texas, and there is a sight that is immediately identifiable:
Vinifera vines stripped almost completely of leaves, standing tall, but looking more like sticks than grapevines. That’s the result of Pierce’s Disease (PD), one of the two or three most deadly grapevine ailments, save for phylloxera.
Vines become infected with PD via two insects—the blue green and glassy wing sharpshooters. These pests nibble on the vine, injecting a bacteria that causes the virus. The virus then clogs the xylem, thereby limiting water and nutrient flow to the rest of the vine, thus resulting in chlorosis, scorched leaves, and eventual vine death after one to five years.
Currently, treatment is limited to traditional pesticides, which need to be sprayed but are only effective after the virus infects the plant. There is a preventive treatment that stops sharpshooters from eating the plant, but needs to be applied via irrigation. The third option is planting vines far enough away from sharpshooter habitats so the insect can’t fly to it.
Now, though, Texas A&M researchers, working alongside a Japanese pharmaceutical company, may have found a way to not only prevent PD, but to cure it in vines that haven’t been infected for too long.
The key to the treatment, called XylPhi-PD, is an otherwise harmless virus that is injected into the infected plant and eats the bacteria that causes PD. James Olson, the marketing director for A&P Inphatec, the U.S. subsidiary of Japan’s Otsuka Pharmaceutical, says it can be used as a “cure” (as long as the vine has had PD for no longer than two years), and as a preventive intervention. In both cases, the bacteriophage cocktail is injected into the vine’s xylem.
The new approach, called bacteriophage therapy, is much more precise than current pesticides, doesn’t require complicated application techniques or protective equipment, is almost completely safe to humans—and is organic. This is especially important in California, where high-value vineyards try to use organic treatments whenever possible. In this, says Olson, bacteriophage therapy could be a groundbreaking treatment not just for PD, but for other plant diseases found in fruit and nut trees.
“This has really been a technical challenge,” he says, citing the need to set up test vines in a controlled situation; find vines in wine regions that suffer from PD and want to participate in trials; determine the best bacteria and figure out proper dosage; and find the right spot to inject the bacteria “cocktail” into the vine.
As testing continues at Texas A&M, as well as UC’s Davis and Riverside, and several commercial California vineyards (including Ridge Vineyards), the process has already been approved the U.S. Environmental Protection Agency, as well as by state regulators in California, Texas, and Arizona as an organic treatment. So far, it has been 60 percent effective in what Texas A&M researchers call two seasons of use in “high-disease-pressure vineyards.”
Otsuka’s interest began in 2007, says Olson, when Ridge founder Paul Draper contacted the company in search for an organic treatment for his PD-infected vines. Meanwhile, lead Texas A&M researcher Carlos Gonzalez, PhD, whose work started in 2010, told a Texas Hill Country seminar in 2015 that the bacteriophage showed promise, but still needed much more development.
“The big test for this will be next spring,” says Sergio Cuadra, the director of winemaking at Texas’ Fall Creek Vineyards, where PD has often been a problem. “That they’ve gotten the results they have is encouraging, since Pierce’s is a nation-wide issue,” says Sergio Cuadra, the director of winemaking at Texas’ Fall Creek Vineyards, where Pierce’s has often been a problem. “The big test for this will be next spring. That’s when everyone will try it to see just how well it works.”
Cuadra says he’s going to be watching to see not just how effective the bacteriophage approach is, but if it’s appreciably more effective than current treatments—especially for the cost.* He notes that the irrigation preventive is generally effective in his vineyards.
Perhaps the most important benefit is that an effective bacteriophace approach will prevent the need to replant, which is almost always necessary when PD inevitably kills vines. That means not only less cost, but higher quality vines (and fruit and wine) in the long run.
For more information, A&P Infatec supplied Wine Industry Advisor with an additional FAQ sheet to share with its readers.
*When asked, sources stated they cannot publicly disclose exact pricing.
Jeff Siegel is an award-winning wine writer, as well as the co-founder and former president of Drink Local Wine, the first locavore wine movement. He has taught wine, beer, spirits, and beverage management at El Centro College and the Cordon Bleu in Dallas. He has written seven books, including “The Wine Curmudgeon’s Guide to Cheap Wine.”