and life cycle—Pierce's disease
Pierce's disease is a lethal disease of grapevines and is
caused by the bacterium Xylella fastidiosa.
It is spread by certain kinds of leafhoppers known as sharpshooters.
The green sharpshooter, Draeculacephala
minerva, and the red-headed sharpshooter, Carneocephala
fulgida, are the primary vectors in
California's Central Valley. The blue-green sharpshooter, Graphocephala
atropunctata, is the most
prevalent in coastal regions such as the Napa Valley. A new
large sharpshooter, the glassy-winged
sharpshooter was introduced into California in the 1990's.
It is now prevalent in southern California and parts of
the San Joaquin Valley. It spreads Pierce's disease more
effectively than the other sharpshooters.
Sharpshooters pick up the bacterium by feeding on symptomless
plant hosts as well as infected grapes and transfer it to
healthy grapes by feeding. Leaves become scorched and dwarfed,
grapes may raisin, and overall vines become stunted and late