EPIDEMIOLOGY OF PIERCES DISEASE IN SOUTHERN CALIFORNIA: IDENTIFYING INOCULUM SOURCES AND TRANSMISSION PATHWAYS

• Author(s): Cooksey, Donald; Costa, Heather;
• Abstract: Xylella fastidiosa can cause a number of plant diseases in a variety of plant hosts including Pierces disease of grapevines, almond leaf scorch disease, alfalfa dwarf, citrus variegated chlorosis, leaf scorch of live oak, pear leaf scorch, and oleander leaf scorch. In Southern California, the primary insect vector of concern is the glassy-winged sharpshooter, Homalodisca coagulata (Say). Previous studies of Xylella fastidiosa-induced diseases have described systems dealing with different primary vector species and different alternate host plants than those that are found in the Southern California systems. In this project, a variety of plant species found near a severe outbreak of Pierces disease in vineyards in the Temecula valley of California were tested to identify potential sources of inoculum in the area. Plants were tested though three summer seasons using ELISA, culture on specialized media, and PCR methods to monitor for the presence of the pathogen. Plant species from the field that consistently tested positive for a grape strain of X. fastidiosa were the previously known hosts grape and almond, and two new hosts, Spanish broom, Spartium junceum and wild mustard, Brassica spp. Samples of oleander, Nerium oleander, also tested positive, however the strain of X. fastidiosa that infects oleander differs from the grape strain and does not appear to infect grape plants. Greenhouse transmission studies indicate that the glassy-winged sharpshooter was able to transmit a grape strain of the pathogen to Spartium junceum, Brassica nigra and other hosts.
• Publication Date: Aug 2003
• Journal: 2003 Pierce's Disease Research Symposium