IMPORTANCE OF GROUND VEGETATION IN THE DISPERSAL AND OVERWINTERING OF XYLELLA FASTIDIOSA

• Author(s): Daane, Kent; Purcell, Alexander; Connell, Joe; Duncan, Roger; Shapland, Elaine; Viveros, Mario; Wistrom, Christina; Yokota, Glenn;
• Abstract: Our goal is to determine the ability of alternate host plants, specifically ground vegetation, in or near almond orchards or vineyards to serve as reservoirs for Xylella fastidiosa (Xf). We surveyed ground vegetation in ALS-infected almond orchards in Californias Central Valley. Plant tissue samples were collected throughout a 2 year period and processed for Xf presence using restriction enzyme digestion of RST31-RST33 polymerase chain reaction (PCR) products and bacterial culture on selective media. Overall incidence of Xf was low in the ground vegetation species, only 63 of 1369 plant samples tested positive. Of the 37 species of common ground vegetation sampled, 11 tested positive for Xf, including such common species as Sheperds purse (Capsella bursa-pastoris), filaree (Erodium spp.), cheeseweed (Malva parvifolia), burclover (Medicago polymorpha), annual bluegrass (Poa annua) London rocket (Sisymbrium irio), chickweed (Stellaria media). There was a seasonal component to bacterial presence, with positive samples found only between November and March. Both ground vegetation and almond trees were most commonly infected with the almond strain of Xf (6 of 7 surveyed sites). ALS-infected almond samples had a Xf concentration within reported ranges, however, we were unable to accurately measure Xf titer in sampled ground vegetation for comparison.
• Publication Date: Dec 2005
• Journal: 2005 Pierce's Disease Research Symposium