2008 Annual Report 1a.Objectives (from AD-416) 1. Assess the incidence and diversity of Xylella fastidiosa in alfalfa, almond, and grape. 2. Determine abundance and seasonal population dynamics of potential vectors. 1b.Approach (from AD-416) Conventional molecular methods will be used to assess the incidence of Xylella fastidiosa in alfalfa and surrounding crops of interest i.e., grape and almond. Standard insect sampling techniques will be used to determine the abundance and seasonal population dynamics of potential vectors. Documents SCA with UC-Berkeley. 3.Progress Report Pierce’s disease of grape and almond leaf scorch disease have been chronic problems in California. Both diseases are caused by the bacterial pathogen, Xylella fastidiosa. The pathogen is vectored by xylem feeding insects and in the San Joaquin Valley of California the most important vector is the green sharpshooter. Green sharpshooter abundance is often high in weedy alfalfa fields and alfalfa is a known host of X. fastidiosa. The potential role of alfalfa as an inocula source was assessed by sampling alfalfa fields seasonally to determine incidence. Incidence of X. fastidiosa was low with only 6 positives detected out of > 3,825 samples screened. The results indicate that alfalfa can indeed serve as a source of X. fastidiosa, but that it is probably not a key inocula source. This project will be monitored by meetings, site visits, and telephone calls with the cooperator.