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Monitoring and Control Measures for Pierce’s Disease in Kern County

The Issue

Pierce’s disease (PD), caused by the bacterium Xylella fastidiosa, is a killer of grapevines. Significant vine loss from PD has occurred in Southern California, North Coast and portions of the southern San Joaquin Valley including Tulare and Fresno counties over the last 100 years. However, the arrival and spread of the glassy-winged sharpshooter (GWSS), a more effective vector of the disease, caused devastating losses in the wine-growing regions of Temecula and threatened Kern County, a major grape production area of the state with more than 87,000 bearing acres and a farm gate value of approximately $438 million dollars.

What Has ANR Done?

A large-scale, joint research project was initiated in 2002 between the UC Cooperative Extension and the California Department of Food and Agriculture to map the incidence and track the spread of Pierce’s disease (PD) within 215 vineyard blocks in Kern County.

The area was selected for evaluation because of its importance as a major grape production area and its short history of GWSS infestation. The acreage surveyed within the project represents over 4,000 acres of grapes or, roughly 5% of the total bearing grape acreage in the county and 15 cultivars of varying ages were examined.

The Payoff

PD Can Be Controlled With Areawide GWSS Treatment and Removal of Diseased Vines

This project has provided multiple positive impacts to grape growers, public agencies working to reduce the populations of GWSS and limit the spread of PD and to those in the research arena. First, the benefits to growers included one-on-one education about the disease and a three-year personalized data set revealing the PD status of individual vineyards and the locations of affected vines for more than 30 growers that cooperated in the project. This data set was used to encourage growers to pull out diseased vines in order to eliminate sources of the bacteria for spread by the GWSS. Since the inception of the project, we have observed an 83% reduction of PD from 2002 to 2003, and a subsequent decrease of 60% from 2003 to 2004 in the vineyards located in the General Beale Pilot Project, an area where the GWSS was first discovered and significant vine losses had occurred due to PD (see photo above).

Secondly, the data set provided an essential layer of information to the USDA Area Wide Management of GWSS Project on the history and location of PD in Kern County. This information was used to designate treatment zones in which it was absolutely critical to keep GWSS populations down to slow the spread of PD. The information generated from the project was modified for presentations at several field meetings to demonstrate that effective PD control can be obtained with a combination of areawide GWSS treatment program and monitoring for and removal of infected vines.

Finally, the data, maps and information has been shared with UC Riverside and UC Berkeley researchers to maximize the opportunity for generating projections of economic loss and new methods of disease management and sampling. The project has generated multiple hypotheses regarding the factors that contributed to the spread of PD in Kern County. There are three projects being conducted at Riverside and Kearney Research & Extension Center to test these hypotheses.


Supporting Unit: Kern County

Jennifer M. Hashim-Buckey, Viticulture Farm Advisor, Kern County
1031 South Mount Vernon Avenue
Bakersfield, CA 93307