Pierce's disease has existed for more than 100 years in the state, but until recently there was no carrier as effective in transmitting the bacteria more than a few feet and spreading the bacteria so rapidly. The glassy-winged sharpshooter, first found in 1990 in Ventura County, has spread throughout Southern California. The insect and the disease are now moving northward. Pierce's disease is caused by a bacterium, Xylella fastidiosa . The typical symptom is for leaves on the plant to begin to dry or to scorch.
Infected vines can die in as little as one to two years.
X. fastidiosa also causes almond leaf scorch, phoney peach disease, alfalfa dwarf, oleander leaf scorch and citrus variegated chlorosis. Pierce's disease decimated 40,000 acres of grapes in the Anaheim, Calif., area in the late 19th century. It was dubbed Anaheim disease, but the name was later changed because of Newton Pierce, who studied the infection. The incurable plant disease has appeared on and off ever since, but its spread was limited. The principal carrier, or vector, was the blue-green sharpshooter, a weak, small insect not able to fly much further than three feet.