Xylella fastidiosa (Wells et al., 1987)
Significance: The bacterium Xylella fastidiosa was found infecting avocado (Persea americana) in Costa Rica. This is a new host record for the pathogen. Xylella fastidiosa is already known to occur in Costa Rica on coffee and citrus plants. Symptoms of leaf chlorosis, leaf margin scorch, leaf deformities, defoliation, shortened internodes, and branch dieback were observed in the avocadoes since the late 1990s. Symptoms were not uniformly distributed within the individual trees. Sampling occurred between 2000 and 2004. Out of the 227 trees sampled, 188 were positive for X. fastidiosa.
Issues of Concern: Xylella fastidiosa is present within North America; however there are many known strains throughout its distribution in North America and other parts of the world. In the above study, the sap of avocado made DNA extractions and PCR tests difficult. Some of extractions were successful and suggested a match to the Pierce’s disease strain in California (Temecula 1) and the citrus variegated chlorosis strain from Brazil.
Subsequent work with the ELISA negative and ELISA positive avocado specimens showed that the bacterium was graft transmissible.
Xylella fastidiosa is known to cause Pierce's disease of Vitis spp. (grapevine), phony disease of Prunus spp. (stone fruit), and citrus variegated chlorosis. Recently the pathogen was also found causing a leaf scorch of Vaccinium (blueberry) in Georgia, United States. This bacterium is vectored by xylem-feeding insects, such as the glassy-winged sharpshooter, Homalodisca coagulata (Hemiptera: Cicadellidae).
Brannen, P.M., G. Krewer, B. Boland, D. Horton, C.J. Chang. 2008. Bacterial Leaf Scorch of Blueberry. Pub C922. January 2008. University of Georgia Cooperative Extension. http://pubs.caes.uga.edu/caespubs/pubs/PDF/C922.pdf
CABI. 2007. Crop Protection Compendium. CAB International, Wallingford, UK.
Montero-Astúa, M., G. Saborío-R., C. Chacón-Díaz, L. Garita, W. Villalobos, L. Moreira, J.S. Hartung, and C. Rivera. 2008. First Report of Xylella fastidiosa in Avocado in Costa Rica. Plant Disease. 92(1): 175.