THE EFFECT OF DORMANT SEASON SURVIVAL OF XYLELLA FASTIDIOSA IN GRAPEVINES ON PIERCES DISEASE EPIDEMICS IN CALIFORNIA

• Author(s): Hill, Barry; Hashim, Jennifer; Peacock, William;
• Abstract: The two California Pierces disease (PD) epidemics associated with population outbreaks of the glassy-winged Sharpshooter (GWSS), at Temecula in the mid-1990s and in Kern County, peaking in 2002, differed in the number of vineyards lost and the grapevine varieties affected. In Temecula, almost half of all vineyards of all varieties were lost to PD, whereas in Kern County only the vineyards of two varieties, Redglobe and Crimson Seedless, suffered losses; all the vineyards of the other four varieties were unaffected. A hypothetical explanation of this epidemiological pattern is that in those parts of California where the winters are more severe, dormant-season die-out of Xylella fastidiosa (Xf) is more likely, and only the earlier-season inoculations and infections survive the winter. The likelihood of Xf die-out is a function of both winter climate and varietal susceptibility. In Kern County, only the most susceptible varieties were affected by secondary (vine to vine) transmission and early season primary transmission (where insect vectors acquire Xf from plant sources outside the vineyard) was of little consequence. Through field experiments, this project expands our knowledge of secondary transmission in the southern San Joaquin valley. The benefit to grape producers in this area will be twofold: 1) more accurate assessment of risk of economic loss from PD, and 2) suggestion of new integrated disease-management practices to control PD.
• Publication Date: Nov 2006
• Journal: 2006 Pierce's Disease Research Symposium