MONITORING AND CONTROL MEASURES FOR PIERCES DISEASE IN KERN COUNTY

• Author(s): Hashim, Jennifer; Hill, Barry; Purcell, Alexander;
• Abstract: Pierces 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 regions and portions of the southern San Joaquin Valley such as Tulare and Fresno counties over the last 100 years. Native sharpshooters, including the blue-green sharpshooter and the red-headed and green sharpshooters have been largely responsible for PD spread. With the arrival of the glassy-winged sharpshooter (GWSS), a more effective vector, the transmission of the bacterium and subsequent disease threatens 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. Approaches to disease management have changed in Kern County, due largely to an increase in the incidence of disease where PD had not known to exist prior to the introduction of GWSS. To date growers have tried to control the insect and the disease with a combination approach of using both soil-applied and foliar pesticides and roguing out vines expressing PDlike symptoms during the summer. However, there is no data to support whether these strategies will be successful to combat the spread of PD. Many management decisions are currently being made based on anecdotal evidence, testimony and projections. The county provides a unique environment in which to map the incidence of PD, track the spread of the disease over time and investigate the interaction between the insect and the disease, given that both inoculum and the insects are present. Such information would be useful to determine the economic impact of GWSS on California agriculture as well as provide fundamental data on epidemiological factors including but not limited to, host susceptibility to disease, GWSS presence, proximity to preferred hosts of GWSS, proximity to alternative hosts of Xylella and individual grower insecticide and disease management programs.
• Publication Date: Dec 2002
• Journal: 2002 Pierce's Disease Research Symposium