Monitoring Xylella fastidiosa insect vectors in Northern and Southern California to understand recent Pierce’s disease incidence

Abstract: Pierce’s disease epidemics, caused by the bacterium Xylella fastidiosa recur periodically in different regions of California. In the North Coast disease incidence is associated with the blue green sharpshooter (Graphocephala atropunctata), while in Southern California with glassy winged sharpshooter (Homalodisca vitripennis). In recent years Pierce’s disease has reemerged in some regions. Recent disease incidence in Northern California does not match the historical pattern associated with blue green sharpshooter. We are investigating possible causes: climate, potential novel pathogen genotypes, and the role of other vectors. In Southern California an increase of the glassy winged sharpshooter in Kern County is thought to be due to reduced insecticide efficacy in combination with warmer winters.