Photograph by David Morgan courtesy UC Riverside
Eats Shoots and Leaves: The glassy-winged sharpshooter has been forestalled—for now.
Trouble That Never Came
Where art thou, oh glassy-winged sharpshooter?
By P. Joseph Potocki
A few weeks back, a mild stink was raised concerning the inclusion of $45 million in earmarks by two local members of Congress, Lynn Woolsey and Mike Thompson. House Representative Mike Thompson put in for the lion's share of these North Bay monies. Thompson's bid to funnel $3,332,000 to public institutions for "Pierce's disease/glassy-winged sharpshooter" research got front-page coverage in a news critique aimed at earmarks benefiting private political donors. While the piece did not criticize the more than $3 million aimed in part to protect North Bay vineyards, the figure represented merely the tip of the glassy-winged sharpshooter funding iceberg.
Eight years ago, a flurry of troubling stories started cropping up. Many foretold, Cassandra-like, the annihilation of our vaunted North Bay wine industry. An unwanted pathogen vector, the half-inch-long leafhopper called the glassy-winged sharpshooter (GWS), seemed poised to invade our climes and kill our vines. The GWS plays host to the deadly bacterium Pierce's disease, an incurable condition made all the worse by this particular vector's lengthy travel habits and hearty buffet-hog appetite.
Traps went up in vineyards, signs got posted on roads, and seemingly overnight, the GWS became a familiar yellow- and ivory-speckled poster child for tasting rooms throughout Sonoma and Napa counties, garnering jaw-time equal to discussion of tannins and terroir. Some time between then and now the GWS faded from the local radar, a fuzzy recollection for many who had kept it on high alert just a few years before.
So what's become of the glassy-winged sharpshooter, that once feared angel of grapevine death? An informal survey conducted at more than a dozen winery tasting rooms in both Napa and Sonoma counties over the last few weeks produced near universal shrugs, smirks and stabs at funny comebacks. Few offered reasons concerning why the GWS threat hadn't materialized, and a few even suggested that it hadn't really posed much of a threat in the first place.
But the GWS hasn't gone away—it's just not here yet. Thanks to ongoing efforts by a range of public and private agencies, this pest has remained a few precious counties removed from us. Hopes are that the GWS never will establish itself in the North Bay. But the glassy-winged sharpshooter does thrive in other parts of California, and this native of the southeastern United States has been residing here in California for quite some time.
Vineyards around Anaheim down in Orange County experienced the first outbreak of Pierce's disease, then called Anaheim disease, way back in the 1800s. More than 40,000 acres of vineyards were destroyed as the disease choked avenues of water flowing through the grape vines. But it wasn't glassy-winged sharpshooters doing the damage in Anaheim. A feeble cousin to the hardy GWS called the blue-green sharpshooter was that century's death-dealing varmint.
The blue-green chews a vine leaf or two, but soon tires of dining following its three-foot-long daily journey. By contrast, its big, bad cousin, the glassy-winged sharpshooter, flies a quarter mile at a time, often in numbers, is considerably larger, consumes up to 10 times its body weight in liquids per hour and injects its needle-like mouth into leaf after leaf after leaf, thus infecting far more plants than the blue-green with the Pierce's disease it carries.
Rhonda Smith is a viticulture farm adviser with UC Davis Cooperative Extension in Sonoma County and an expert on both Pierce's disease and the GWS. Smith assures, "The glassy-winged sharpshooter is not present in Sonoma County nor anywhere on the North Coast to anyone's knowledge. There are traps up for it. The Agriculture Commissioner's office in this county, in Napa County and in other North Coast counties are all quite good at looking for egg masses in incoming shipments of ornamental plants from infested counties in Southern California. Ornamental plants are also inspected and treated at the point of origin in Southern California before they're loaded on trucks and shipped here."
Any possibility the GWS might ever settle in the North Bay still strikes fear in the local wine industry. And for good reason. Once the GWS arrives, it's one interloper that's difficult to vanquish. Take Temecula, for example. Ten years ago, Pierce's disease wiped out fully one-third of Temecula's vineyards, causing losses totaling $20 million. It was hoped that vineyard eradication efforts had long ago paid off, but almost 40 GWS were found trapped in Temecula vineyards during the last week of this past April. In addition to its voracious appetite for grape leaves, the GWS has an equal taste for precious ag crops like citrus, almonds and stone fruit. So it's not hard to see why this issue's still delivering plenty of political punch along with wine-industry attention.
Approaches to the problem vary from place to place. Whereas Temecula vineyard owners tend to favor pesticides like Admire in combating the GWS, here in the North Bay, groups like the Sonoma County Winegrape Commission, a member organization representing over 1,800 grape growers, place a greater emphasis on integrated pest management. The commission champions the use of natural biological controls on pests like the glassy-winged sharpshooter. Insectories, or gardens filled with plants that attract and thus employ "good" bugs to feed on their destructive brethren, help eliminate pest species.
Providing homes for insect eating birds and hungry little bats helps, too. One recent demonstration was described in which a team of search and rescue dogs from Twin Pines Vineyards in Napa sniffed out what Winegrape Commission president Nick Frey contends is now the single most threatening insect facing grape production in the North Bay: the vine mealy bug.
The last North Bay contacts with the glassy-wing came back in 2007. In February of that year, a mature GWS was captured in Napa. The next month, a sharpshooter egg mass was discovered in a shipment of ornamentals at Lowe's in Cotati. Neither incident led to an outbreak. Apparently, those millions of federal dollars going into Pierce's disease research and eradication efforts matched with ongoing local vigilance have prevented what once seemed an inevitable regional infestation. While the GWS will continue to pose a threat to North Bay vineyards for the foreseeable future, don't expect to be spending a lot of time discussing it with tasting-room folk. At least for now, they'd rather talk tannins and terroir.
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