Avenue Vine

During the Symposium, attendees heard about advances being made in the areas of developing PD-resistant wine grapevines and methods of inoculating vines against PD, as well as advancements being made in disease and vector management, monitoring and biology.

The two-day Pierce’s Disease Research Symposium drew over 150 people. It was coordinated by the California Department of Food and Agriculture’s (CDFA) Pierce’s Disease Control Program and partially supported by the PD/GWSS Board. It is held annually to facilitate the flow of information, accelerate progress and increase scientific collaboration.

“Research is paving the way for us to manage Pierce’s disease, and hopefully it may someday also find a solution,” said Bob Wynn, head of CDFA’s Pierce’s Disease Control Program. “The Symposium provides all of our researchers with an ideal setting to report on their advancements and to network with other researchers. It also acts as a catalyst to help these scientists generate new ideas about how they can help growers deal with Pierce’s disease and the glassy-winged sharpshooter.”

As part of the PD Research Symposium, a 321-page proceedings was published. Copies of the proceedings can be downloaded from the CDFA Web site at www.cdfa.ca.gov/gwss/.

The PD/GWSS Board was established in July 2001 to support scientific research to find a cure for Pierce’s disease. An annual assessment paid by winegrape growers supports its research efforts. The PD/GWSS Board also advises the California Department of Food and Agriculture on a variety of other issues pertaining to Pierce’s disease and the glassy-winged sharpshooter.

The work of the Board is underlined by the fact that Pierce’s disease has no known cure and, if left unchecked, could be devastating to the grape industry and several other California crops. A study released in December 2006 by the Wine Institute and the California Association of Winegrape Growers showed that the total annual economic impact of California’s winegrape industry is estimated at $51.8 billion.*

About Pierce's Disease:
Pierce’s disease, caused by the bacterium Xylella fastidiosa, is a deadly disease of grapevines. It is spread by certain types of xylem feeding leafhoppers (Cicadellidae) known as sharpshooters. The disease is known to be present from California to Florida and south as far as Central America. Its presence has been known since the 1880’s where in Southern California it destroyed 35,000 acres of vineyards. At that time the disease was known as Anaheim Disease, Mysterious Disease and the California Vine Disease. It was eventually named for N. B. Pierce, who extensively studied the disease.

The bacteria, X. fastidiosa, is limited to the xylem or water conducting vessels of plants. Symptoms begin to develop about mid-summer as the bacteria blocks these vessels and a drying or scorching of the leaves is seen. Leaves become chlorotic along the outer edges or adjacent to the dead tissue. The drying or scorching of the leaf continues for a few days to weeks until the leaf eventually falls, usually leaving the petiole attached to the cane. Petioles gradually die back and fall. Maturing canes that turn tan will have green islands along the infected portions. When new growth occurs on infected canes it can be delayed and is usually stunted. Leaves on stunted shoots can have a yellow mottling between the major veins. Depending on the variety of grape, death of the entire vine usually occurs in 1 to 5 years.

In 1997 a survey was conducted to determine the number of leafhopper species, the size of the populations, and their movements in and around vineyards. Fourteen vineyards, twelve in the Texas Hill Country and two in north central Texas, were visited on a bimonthly basis. At each vineyard sweep nets of 30 ft. transects, at least one on each side of the vineyard, were conducted and the leafhoppers collected. Plant species were also noted along each transect in order to determine the preferred host plant of each leafhopper species. Yellow sticky cards were placed at approximately 100 ft intervals and usually one row in or 4 to 5 vines inside the vineyard along the perimeter. The sticky cards were observed and data collected at each visit to the vineyard. Plant samples were collected from each vineyard and will be tested, using Polymerase Chain Reaction (PCR), by the Phytopathology Lab at Texas A&M University.

From this survey, approximately 52 species of leafhoppers were collected and most identified. Samples of all leafhoppers were sent to the USDA ARS Systematic Entomology Laboratory in Beltsville, Maryland for positive identification. Other data collected is presently being analyzed. It is hoped that this survey will provide information as to specifically which leafhoppers are vectors of Pierce’s disease and which plant species play host to these insects.**

Contact:
Ken Freeze
Brown-Miller Communications
(800) 710-9333

*Source: Press Release; “Pierce’s Disease Research Symposium,” Sacramento, Calif--December 12, 2006 –

**Source: ”Pierce's Disease,” James C. Medley, AgroEcoSystems Research Group, TEXAS A&M UNIVERSITY, September 11, 2003 - Photos credit: James C. Medley

Additional Articles on “Pierce’s Disease”
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“GWSS Board Selects Nancy Irelan as Research Director,” October 04, 2006

“In Arizona Glassy-Winged Sharpshooter Infestation Numbers on the Rising,” July 21, 2006

“Glassy Winged Sharpshooter Takes Aim On Arizona’s Vineyards, Oleanders and Citrus Crops,” June 27, 2006

“California Firm Captures Nation’s Highest P.R. Honor,” June 19, 2006

“Latest Agriculture Bill Benefits California State Wineries,” May 19, 2006

“Leading Pierce's Disease Researcher Set to Retire,” May 11, 2006

“PD/GWSS Board Seeks Research Director,” March 14, 2006

“CAWG Weighs in on Early Hearings for 2007 Farm Bill,” March 08, 2006

“Glassy-winged Sharpshooter Update & Symposium,” December 04, 2005