Pierce's disease has been confirmed in a dozen vineyards east of Bakersfield, according to a summer-long monitoring program led by University of California Cooperative Extension Viticulture Farm Advisor Jennifer Hashim.

UC and other officials are working with farmers to remove and destroy the approximately 600 infected vines to avoid further spread of the incurable and fatal disease. In addition, Hashim is conducting educational programs, consulting with farmers, and distributing materials on Pierce's disease identification and management strategies.

“We will work with growers to develop field monitoring programs and control strategies,” Hashim said. “Growers should carefully watch their vines and submit samples of vines that exhibit Pierce's disease symptoms to CDFA (California Department of Food and Agriculture) for analysis.”

Pierce's disease is caused by the bacterium Xylella fastidiosa, which clogs the plant's water conductive tissue, choking off the movement of water and nutrients from the roots to grapevine canes and leaves. Insects that have the bacteria on their mouths transmit Pierce's disease to grapevines when they feed on fluid in the plant xylem. In California, Xylella fastidiosa can also cause Almond Leaf Scorch and Oleander Leaf Scorch.

Pierce's disease is spread in Kern County by native sharpshooters and the glassy-winged sharpshooter, a pest introduced to the area about five years ago. Sixteen infected grapevines identified in summer 2000 in one Kern County vineyard were destroyed last year.

“Our 2001 survey results indicate that glassy-winged sharpshooters are very effective transmitters of Pierce's disease,” Hashim said. “Growers should quickly remove any vines that are diseased. That's the best way to minimize the sharpshooters' opportunities to acquire the bacterium and pass it on to more vines.”