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Causal Role of Xylella fastidiosa in Oleander Leaf Scorch Disease

January 1999 , Volume 89 , Number  1
Pages  53 - 58

A. H. Purcell , S. R. Saunders , M. Hendson , M. E. Grebus , and M. J. Henry

First, second, and third authors: Department of Environmental Science, Policy and Management, University of California, Berkeley 94720-3112; fourth author: Department of Plant Pathology, University of California, Riverside 92521; fifth author: University of California Cooperative Extension, 21150 Box Springs Rd., Moreno Valley 92557

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Accepted for publication 6 October 1998.

A lethal leaf scorch disease of oleander (Nerium oleander) appeared in southern California in 1993. A bacterium, Xylella fastidiosa, was detected by culturing, enzyme-linked immunoassay, and polymerase chain reaction in most symptomatic plants but not in symptomless plants or negative controls. Inoculating oleanders mechanically with X. fastidiosa cultures from diseased oleanders caused oleander leaf scorch (OLS) disease. The bacterium was reisolated from inoculated plants that became diseased. Three species of xylem sap-feeding leafhoppers transmitted the bacterium from oleander to oleander. The bacterium multiplied, moved systemically, and caused wilting in Madagascar periwinkle (Catharanthus rosea) and leaf scorch in periwinkle (Vinca major) in a greenhouse after inoculation with needle puncture. No bacterium was reisolated from grapevine (Vitis vinifera), peach (Prunus persica), olive (Olea europaea), California blackberry (Rubus ursinus), or valley oak (Quercus lobata) mechanically inoculated with OLS strains of X. fastidiosa. A 500-bp sequence of the 16S-23S ribosomal intergenic region of oleander strains showed 99.2% identity with Pierce's disease strains, 98.4% identity with oak leaf scorch strains, and 98.6% identity with phony peach, plum leaf scald, and almond leaf scorch strains.

Additional keywords: Graphocephala, Homalodisca coagulata, Homalodisca lacerta, sharpshooter, vector transmission.

© 1999 The American Phytopathological Society