SIGNIFICANCE OF RIPARIAN PLANTS IN THE EPIDEMIOLOGY OF PIERCES DISEASE

• Author(s): Baumgartner, Kendra; Purcell, Alexander; Walker, Andrew;
• Abstract: The goal of this research is to evaluate the significance of riparian hosts in the epidemiology of Pierces disease (PD) in the North Coast grape-growing region of California. The first objective is to examine the epidemiological role of seasonal changes in Xylella fastidiosa (Xf) concentrations in riparian hosts. Among systemic riparian hosts, differences in seasonal Xf concentrations and Graphocephala atropunctata (blue-green sharpshooter, BGSS) feeding preference affect their importance as Xf reservoirs. Temperature affects Xf concentrations in plant hosts and, in turn, Xf concentrations affect the probability of a BGSS acquiring Xf while feeding on an infected plant. We focused on Xf concentrations in five systemic hosts: Rubus discolor (Himalayan blackberry), R. ursinus (California blackberry), Sambucus mexicana (blue elderberry), Vinca major (periwinkle), and Vitis californica (California grapevine). We needle inoculated potted plants of California grape, California blackberry, Himalayan blackberry, blue elderberry, and periwinkle in the greenhouse and transferred all infected plants to two sites in the North Coast (Napa County, Mendocino County). Xf was not detected in the majority of plants after several months in the field (from July to Oct. 2003), except for periwinkle which maintained a high number of infected plants through all seasons. Xf concentrations were highest in periwinkle in all seasons and at both sites, and were sufficient for BGSS acquisition year-round. California grape and Himalayan blackberry supported Xf concentrations that were sufficient for BGSS acquisition in autumn and summer, but not in spring. These results suggest that BGSS likely acquires Xf from riparian hosts in autumn, instead of spring.
• Publication Date: Dec 2004
• Journal: 2004 Pierce's Disease Research Symposium