Temecula grape growers recovering "The report of my death was an exaggeration."

Mark Twain, May 1897 Reports of the demise of the Temecula Valley wine grape industry in Riverside County, Calif., are also exaggerated.

A year ago there were concerns for the survival of the small enclave of 3,000 acres of vines and 14 wineries in Southern California under attack by the most ominous disease threats to face grape growers in a more than a century.

Today's there's optimism in Temecula. That is good news not only for Temecula, but for the rest of California's grape growers who this coming season could very well face the same threat as the handful of Temecula producers have endured over the past two seasons.

Not only were Mount Palomar Winery president and general manager Peter Poole's vines at the vortex of the threat from the Glassy-winged Sharpshooter and the Pierce's Disease it vectored, but he was the head of a vintner/grower group that lead the battle against the pests and for the region's survival.

"While we first found Pierce's Disease in an abandoned vineyard in 1998, my vineyard and the neighboring Callaway vines were the hardest hit," said Poole. Vine deaths in his small vineyard from Pierce's Disease (PC) went from a half dozen to 200,000 in one year's time.

Through it all, Poole remained optimistic that his family vineyards and winery would survive, as would those of his peers.

Lost 30 percent Poole lost 30 percent of his vineyard to the disease vectored by the most voracious sharpshooter ever found in the U.S. One-third of all grapevines in Temecula Valley have been lost to PD.

"Not all varieties and vineyards were affected, but for those who did get hit it was devastating," he said.

Temecula became ground zero for a story that is yet to record the final chapter for California. Since that first GWSS was identified, it spread throughout California, so far in small numbers. It likely is being spread by shipments of ornamentals from Southern California. This coming season will be the most telling yet as to how far the pest and disease will spread into the state's 800,000 acres of vines.

The threat is not being taken lightly. To date federal and state agencies have allocated $32 million into research and control of the pest and disease.

Temecula has made a Phoenix-like recovery since the disease and pest were first identified. No one is planning to plant large blocks of new vines in Temecula yet, but Poole and others are replanting vines lost to PD with a sharp drop in GWSS numbers.

"They sampled citrus in our area this fall as well as in the Fallbrook area where there has been no control program like we had last year. The ratio of finds was 15 to 1 for Fallbrook vs. here," said Poole, who added that researcher have been forced to go elsewhere to study GWSS in citrus.

That's the main reason for optimism among Temecula vintners and growers. It took a Herculean effort and piles of money to turn back the "terrifying" GWSS/PD threat. Temecula has survived and with that comes words of wisdom from Poole and others for the majority of California grape growers who most likely will face the firestorm he has survived.

"Throw out everything you think you know about the native sharpshooters and Pierce's Disease," he said. "These are not the same pest and disease you may have seen in the past."

And Poole also cautioned his peers elsewhere to "be very aware of what is going on outside of your own property. Even today when I go into town, I look into the trees and shrubs in the shopping center to see if I can see any glassy-winged."

When reminded of the 200-mile long stretch of GWSS-host oleanders along Highway 99 through the heart of the California grape industry in the San Joaquin Valley, Poole simply shook his head.

"You cannot let GWSS build up in large numbers in your vineyards," he said. "It will be terrifying to see what will happen. If it gets into your vineyard, you have to be very aggressive in treating it."

GWSS prefer succulent, young growth. "I had an acre of newly grafted that when the canopy got out to three feet, I had 10 to 20 sharpshooters per vine - and it takes only one to kill a vine."

Pierce's Disease scientifically dates back decades. It was know originally as Anaheim Disease or the California wine disease, initially destroying 40,000 acres and closing 50 wineries in Southern California before 1900.

Since then, it has at worst been a sporadic problem. It has had its biggest impact in coastal regions. While it has killed vines in the Central Valley, it has not been a significant problem for decades.

Heretofore PD has been a basically slow moving diseased spread by lethargic sharpshooter GWSS cousins.

However, no one has seen it before in the Temecula Valley, which does not bode well for areas where it is known to occur.

"We still don't know for sure where the Pierce's Disease came from. We had never seen it before. But, when the glassy-winged came into this valley, PD devastated vineyards," said Poole.

GWSS is a voracious cane feeder, using its straw-like mouthparts to consume large volumes of fluid. The hourly feeding rate exceeds its body weight by tenfold. In the process, it infects vines with Pierce's Disease, which shuts down the water movement mechanism within the vines and the plant dies.

Unlike native sharpshooters, GWSS feeds from vine to vine and it only takes one sting go infect a vine with Pierce's Disease.

"They are very fast and when they detect movement in the vineyard they move behind a cane," said Poole. "Put your hand behind a cane and they'll move back around the cane."

Look in morning Poole's vineyard crew learned quickly how to spot them, often before traps pick them up. GWSS sticky traps are considered "blunder traps" since there is no pheromone associated with them.

"Look for them in the morning. They move slower then," he said.

Leaf stunting and scorching of the outer leaves are two PD symptoms. Grape clusters will wilt and dry up after fruit set as vines appear stunted and stressed. Infected canes are shorter than uninfected canes.

"The most telltale signs I've found that a vine has PD is when the leaves drop off the canes, but the petiole remains on the cane," said Poole.

"Once we start seeing symptoms, we immediately tag cordons for removal in the winter. Once all the leaves drop, you cannot identify PD-infected vines," he said.

Cutting cordons rather than just infected canes can save the rest of the vine. Poole does not select a cane for another cordon the year immediately after the infected cordon is removed.

"If the vine does not have any symptoms the year after the cordon or cordons are moved, we'll select a cane for another cordon the following winter," he said.

Citrus is the primary overwintering host for GWSS. There are about as many acres of citrus in Temecula, 3,200, as there are grapes. Poole farmed 31 acres if citrus, all adjacent to his vineyards. That's all gone.

More than 2,000 acres of citrus was treated with Admire last year. This was done in the spring to catch GWSS nymphs. "Timing is critical with this treatment because adults do not like Admire and the first sign of it will leave citrus and go to vineyards, which would be devastating," he said.

Poole, whose vineyard was one of the hardest hit in the beginning, also treated his vines twice with Dimethoate last season.

While this citrus insecticidal treatment was successful, Poole said a native parasitic wasp did considerable damage to GWSS in the summer of 1999. "We got good 85 to 90 percent parasitization before last summer and that diminished the population considerably. "Nevertheless, the numbers that were left still represented a major threat to the vines," he said. "The spring Admire application was very critical in us turning the corner on the threat."

The combination of the wasp and the pesticide in citrus as well as removal of infected vines and citrus combined to bring Temecula back from the brink of ruin.

The citrus will be treated again this year.

"People here are positive enough that we are willing to begin replanting individual vines lost to PD, but I don't think anyone is at the point of planting brand new vineyards," he said.

"It is pretty obvious we cannot treat the citrus for the next 20 years. From a business standpoint, I think most here are going to wait before making a huge financial commitment. I know I am, but people are beginning to talk about new vineyards," he said.

Temecula growers learned quickly that Chardonnay is the most susceptible varietal. It represented 60 percent of the valley before GWSS/PD came in. Twenty-year-old-years old Chardonnay vines died with 12 months after a PD infection.

"We have been told it may take four years for some other varietals to die from a PD infection," said Poole. "However, we are beginning to doubt that since losses have been fairly small in Merlot and Cabernet Sauvignon."

The most resistant variety is Riesling, he said. It was under high GWSS pressure but losses were minimal. It has shown such high resistance, there are experiments under way using a Riesling scion grafted in the middle of a vine as a PD blocking technique.

"I have a Chardonnay vineyard I grafted over from Riesling. It has survived longer than other Chardonnay, and I am convinced the reason for that is the Riseling roots," he said.

Grape growers are like any farmer. They always look for silver linings and Temecula producers are seeing the GWSS/PD near-disaster as a blessing, albeit a frightening one - in disguise.