EPIDEMIOLOGY OF PIERCE'S DISEASE IN THE COACHELLA VALLEY

• Author(s): Gispert, Carmen; Perring, Thomas; Farrar, Charles; Krell, Rayda;
• Abstract: In 2001, no Pierce's disease (PD) was detected in the Coachella Valley. However in June 2002, one diseased grapevine was found in each of two adjacent vineyards. A subsequent census of those vineyards revealed the presence of 13 infected vines. Each of the infections was confirmed with ELISA and bacterial culturing, and PCR was used to confirm the presence of the grape strain of Xylella fastidiosa (i.e. Pierce's disease). Surveys in June 2003 identified two additional fields with infected vines, bringing the total number of locations in the valley to three. Yellow sticky traps have been used to show the seasonal trend of glassy-winged sharpshooter (GWSS) adults. Average counts in the summer of 2002 were higher than in the summer of 2001. Similarly, winter traps in 2003 showed higher densities than winter traps in 2002, suggesting an increasing GWSS population density throughout the valley. However, spring and summer 2003 traps were nearly zero at all locations, indicating successful control of GWSS by the CDFA sponsored vector control program implemented by the Riverside County Agricultural Commissioner's office. Through this study, traps adjacent to citrus groves caught more GWSS than traps not near citrus, however fewer than 35 percent of the traps near citrus caught GWSS on any given week. GWSS count data were managed in a GIS format and this enabled us to place relative importance to citrus groves based on various densities of GWSS caught near the groves. This information could be used to target sites for vector reduction treatments.
• Publication Date: Aug 2003
• Journal: 2003 Pierce's Disease Research Symposium