Identifying sources of Xylella fastidiosa in Southern California Vineyards

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The Issue

In the early 2000s, the grape industry in the Temecula Valley suffered tremendous economic losses resulting from an epidemic of Pierce’s disease, a lethal disease of grapevines caused by the bacterium Xylella fastidiosa. Leafhopper insects, primarily the glassy-winged sharpshooter, transmit this pathogen from plant to plant. The bacterium can also infect several other species of plants that can serve as sources of inoculum for infection of grapevines. The identification and removal of infected plant material from grape-growing areas is critical to the successful management of Pierce’s disease.

What Has ANR Done?

Over a period of three growing seasons, native, introduced, and cultivated plants growing in or near infected vineyards were surveyed at 10 locations thoughout the Temecula Valley. Plants were sampled repeatedly and tested to identify potential hosts of Xylella fastidiosa that could be possible sources of inoculum. More than 4,500 plant samples were screened for the presence of the pathogen using ELISA (Enzyme Linked Immuno-Sorbent Assay), culture on specialized media, and DNA amplification methods.

The Payoff

Two new hosts of Xylella in vineyards

Species that consistently tested positive for Xylella fastidiosa were the known hosts -- grape, almond, and oleander -- and two new hosts -- Spanish broom, Spartium junceum, and wild mustard, Brassica spp. Preliminary greenhouse studies indicate that the glassy-winged sharpshooter is able to acquire the pathogen from both of these hosts and transmit it to grapevines. Growers were advised to remove these plants from grape-growing areas or monitor them for signs of infection, as they may serve as sources of inoculum for infection of grapevines.

Contact

Supporting Unit:

Riverside County

Dr. Carmen Gispert
UC Cooperative Extension
82-675 Highway 111, Room 118
Indio, CA 92201
(760) 863-8293
cgispert@ucdavis.edu

Dr. Don Cooksey
Department of Plant Pathology
University of California
Riverside, CA 92521
(951) 787-3516
Cooksey@citrus.ucr.edu