Submitted to: Entomology Society of America Pacific Branch Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 12/28/2004
Publication Date: 2/26/2005
Citation: Groves, R.L., Cabrera, J. 2005. Seasonal population biology of Xylella fastidiosa and insect vectors; Implications for secondary spread of the almond leaf scorch pathogen [abstract]. Entomology Society of America Pacific Branch Eighty-ninth Annual Meeting. p. 32. Interpretive Summary:
Technical Abstract: Almond leaf scorch (ALS) disease has emerged as a serious threat to almond production areas throughout California’s San Joaquin Valley and is caused by the xylem-limited bacterium Xylella fastidiosa (Xf). The bacterium has a diverse host range and is transmitted by xylem feeding sharpshooters (Cicadellidae) and spittlebugs (Cercopidae) in California. Populations of Xf were monitored monthly within individual ALS-affected trees in both a Fresno and Kern County orchard through the interval March-November, 2004. Bacterial isolation on solid media, DAS-ELISA, and real-time, PCR based protocols illustrated increasing populations of Xf among almond cultivars. Results from insect dispersal studies conducted in 2004 illustrated that adult green sharpshooters (Draeculacephala minerva; GSS) and spittlebugs (Cercopidae) were the only potential Xf vectors captured dispersing into ALS-affected orchards. Peak dispersal of GSS coincided with peak populations in adjoining acreages of permanent pasture or forage alfalfa. Both GSS and glassy-winged sharpshooter (Homalodisca coagulata) transmitted Xf at low frequencies to susceptible indictor plants averaging 4.3 and 9.4%, respectively. An accurate knowledge of which vector species transmit ALS strains, where they acquire the pathogen, when they move into orchards, and how they spread the pathogen among susceptible almonds is critical to understanding and managing the spread of this disease.