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EPIDEMIOLOGY OF PIERCE'S DISEASE IN THE COACHELLA VALLEY
Project Leaders:
Thomas M. Perring
Department of Entomology
University of California
Riverside, CA 92521
Carmen Gispert
Viticulture Farm Advisor
UC Cooperative Extension, Riverside County
Riverside, CA
Cooperator:
Charles A. Farrar
Department of Entomology
University of California
Riverside, CA
Reporting Period: The results reported here are from work conducted from May 1, 2001 through September 30, 2002.
INTRODUCTION
The table grape industry in the Coachella Valley is represented by 10,465 acres of producing vines, which generated grapes
valued at $108.5 million in 2001 (Riverside County Agricultural Commissioner, 2001). The glassy-winged sharpshooter was
identified in the Coachella Valley in the early 1990's (Blua et al. 1999), and we have documented increases in the numbers of
this efficient PD vector over the past 17 months. In July 2002, we confirmed the occurrence of X. fastidiosa (PD strain) in 13
vines from 2 adjacent vineyards in the southeastern part of the Valley. With this discovery, and the increasing numbers of
GWSS, the CDFA Pierce's Disease Program in concert with the Riverside County Agricultural Commissioner's Office is
developing an area-wide vector suppression program. The data gathered in our epidemiological studies provide fundamental
information that are valuable for this program.
OBJECTIVES
The goal of our epidemiological studies in the Coachella Valley is to discover characteristics that are unique to geographic
areas with and without PD, and to use this information to design management strategies to reduce disease spread.
Two objectives are pertinent to this report:
1. Determine the incidence and distribution of Pierce's disease (PD) in the Coachella Valley.
2. Describe the spatial and temporal abundance of GWSS in the Coachella Valley and determine site characteristics that
contribute to GWSS abundance.
RESULTS AND CONCLUSIONS
PD incidence and distribution:
For the pa