ARS | Publication request: Assessment of the role of alfalfa in the spread of Xylella fastidiosa in California

Submitted to: Phytopathology
Publication Type: Abstract Only
Publication Acceptance Date: May 15, 2008
Publication Date: July 1, 2008
Citation: Sisterson, M.S., Thimmiraju,, S.R., Daane,, K., Groves,, R.L. 2008. Assessment of the role of alfalfa in the spread of Xylella fastidiosa in California. Phytopathology 98:S147-S147.

Technical Abstract: Grape and almond are planted on a large scale throughout much of California. Both crops are susceptible to diseases caused by Xylella fastidiosa. Within California’s Central Valley, the green sharpshooter (Draeculacephala minerva) is a key vector. This insect is often found in large numbers in cultivated alfalfa fields and alfalfa is a known host of X. fastidiosa. We conducted studies to assess the potential for alfalfa to serve as a source of X. fastidiosa inoculum or as a source of vectors. Analysis of Geographic Information Systems maps indicates high overlap in the distribution of grape and almond with alfalfa in Fresno, Kern, and Tulare counties. Within these counties, monitoring of green sharpshooter populations in alfalfa fields determined that green sharpshooter abundance is typically highest on weedy-field margins. In addition, screening of field collected alfalfa using standard PCR methods, determined that incidence of X. fastidiosa in alfalfa is typically low. Thus, our results suggest that alfalfa fields may act as an important source of the vector but current evidence suggests a minor role for alfalfa as a source of inoculum.