Wine : Grape Disease Threatens State’s Wineries

A major outbreak of Pierce’s Disease has devastated vineyards in the Temecula Valley, destroying more than 200 acres of vines and resulting in an estimated $1.2 million in damage to grapes alone, to say nothing of the cost of replanting what has been ruined.

This year’s harvest in the region could be as much as 15% below normal, says Ben Drake, an area vineyard manager.

What’s worse, because the disease is being spread by a new bug, there is potential for it to spread beyond the isolated growing area in southwestern Riverside County and infect the vineyards in the rest of the state.

Callaway, Temecula’s largest winery, has been particularly hard hit, losing more than 40 acres.

“If a solution to the problem isn’t found in the near future, the Temecula Valley will be completely without vines three years down the road,” says John Moramarco, general manager at Callaway and one of the region’s pioneer viticulturists.

Pierce’s Disease is caused by a bacterium native to the Americas, Xylella fastidiosa, which clogs the water-conducting tissue of a plant and ultimately causes it to dry up and wither away.

Traditionally, it is spread by insects known as sharpshooters. The bug that is spreading the disease in Temecula--called the glassy-winged sharpshooter--is bigger, badder and more vigorous than any other sharpshooter yet seen.

Matthew Blua, a postdoctoral research associate at UC Riverside, who has worked closely with Temecula growers on the problem, says it “flies higher, stronger and farther than anything we’ve seen before.”

The glassy-winged sharpshooter seems to have arrived in Ventura County sometime in 1990 on nursery stock from its native southeastern United States. From there, it spread rapidly on both ornamental and agricultural plants throughout Ventura, Los Angeles, San Bernardino, Riverside, Orange, San Diego and southern Santa Barbara counties and was identified this summer as far north as southern Kern County.

In the words of state Sen. Ray Haynes (R-Riverside), “This big bug is moving . . . and it’s moving north.”

Patrick Gleason, director of the Napa-based American Vineyard Foundation, calls the glassy-winged sharpshooter a “pterodactyl among sharpshooters” and says its numbers “have gone through the roof in the state.”

Further, he says, if grape growers in other parts of the state don’t seem concerned or even aware of its presence, it’s simply because it “isn’t on their radar screens yet. Once they become aware of the impact that it has had in the Temecula region, the learning curve will go straight up.”

Pierce’s Disease is not new to California. It was identified in 1883 when vines in Anaheim began to wilt. Eventually, it wiped out more than 40,000 acres of vineyards in the Los Angeles Basin, up to that time the center of the state’s wine industry.

With that in mind, a bill is being drafted by Assemblyman Bruce Thompson (R-Fallbrook), which will requisition $2.2 million in state funds to look into the problem. Also, Assemblyman Rod Pacheco (R-Riverside) is working on a petition to the governor to declare the Temecula Valley a state of emergency.

There is also a team of academics put together two years ago by the American Vineyard Foundation to do long-term research on Pierce’s Disease. Bruce Kirkpatrick, a plant pathologist from UC Davis, is the group’s leader.