Pierce's Disease

Definition - What does Pierce's Disease mean?

Pierce’s Disease (PD) is a bacterium-based disease that is spread by leafhoppers called Sharpshooters. The insects feed on the vines, injecting the bacterium Xylella fastidiosa into the vine. This bacterium feeds on the xylem of the plant - the part of the vine that transports water, the way our veins transport blood. Over time, a gel forms in the xylem tissue, preventing water from moving up the vine. The leaves turn yellow and brown, falling off the vine; shoots die. After one to five years, the vine dries up completely and dies.

The disease affects grape vines in the America continents, primarily in the regions with mild winters.

WineFrog explains Pierce's Disease

Discovered in 1982 by Newton B. Pierce, California’s first professional plant pathologist, PD was not a threat to California’s wine regions until the glassy-winged sharpshooter (GWSS) was found in Temulcula Valley in 1996.

Since then, PD plagues wine regions in California on an annual basis. Over 1,500 acres of vines have been destroyed by the disease, with 15 counties infested in 2000. The estimated economic impact on California’s wine industry has come in around $33 billion.

As of 2013, no permanent cure has been discovered, though the following steps have been taken:
  1. System put in place to warn winemakers of possible infestation and the migration of the GWSS
  2. Development of resistant vines that are up to 94% Vitis Vinifera
  3. Biological control of the GWSS through the importation of natural predators and use of insecticides for small plots of land
  4. Chemotherapy method for the infected vines (experimentation stage)
Some grape varieties are more resistant to the bacterium than others. Unfortunately, Chardonnay and Pinot Noir are especially sensitive. The Vitis rotundifolia grape family, native to America South, is naturally resistant to the bacterium, which is why they are being used create the resistant Vitis Vinifera vines.

PD is the most damaging disease caused by Xylella fastidiosa, though it isn’t the only one. This bacterium also causes phoney peach disease, bacterial leaf scorch, orelander leaf scortch and citrus variegated chlorosis disease.
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