Determining the threat of Pierce's disease to Virginia vineyards

Pierce’s disease (PD) is a vascular disease of grapevines caused by Xylella fastidiosa (Xf) which is transmitted by xylophagous insect vectors. PD infection in Virginia vineyards was thought to be isolated to southeastern portions of the state as there have been no reports of vine loss in western Virginia and cold winter temperatures experienced there limit the effects of the bacterium from year to year. Upward trends in winter temperatures have raised PD concern in the mid-Atlantic. Surveys of ten commercial Vinifera vineyards during the 2006 and 2007 growing seasons sought to identify risk of PD infection to areas considered “low risk.” Characteristic PD symptoms were observed in all sites in both years and presence of the causal agent, Xylella fastidiosa, was confirmed using DAS-ELISA. Several species of capable insect vectors were trapped within all sites and the sharpshooters Oncometopia orbona (Fabr.) and Graphocephala versuta (Say) (Hemiptera: Cicadellidae) were determined to be species of interest. This study recommends that Mid-Atlantic grape growers monitor winter temperatures to predict severe PD infection.