|HAVILAND, DAVID - University Of California - Cooperative Extension Service|
Submitted to: CDFA Pierce's Disease Control Program Research Symposium
Publication Type: Abstract Only
Publication Acceptance Date: 11/1/2018
Publication Date: 12/1/2018
Citation: Sisterson, M.S., Burbank, L.P., Krugner, R., Stenger, D.C., Haviland, D. 2018. Epidemiology of Pierce’s disease in the General Beale area of Kern County. CDFA Pierce's Disease Control Program Research Symposium. p. 139.
Technical Abstract: Introduction of the glassy-winged sharpshooter to California resulted in epidemics of Pierce’s disease in the Temecula Valley and the southern San Joaquin Valley (Kern County) in the late 1990’s and early 2000’s, respectively. In response, an area-wide suppression program was implemented that primarily relied on application of insecticides. Analysis of trapping data from 7 vineyards, 2 conventional citrus orchards, and 2 organic citrus orchards located in Kern County indicated that the area-wide program suppressed sharpshooter populations from 2002 to 2008. However, glassy-winged sharpshooter abundance increased in 2009 and peaked in 2015. In association, incidence of Pierce’s disease rose. Glassy-winged sharpshooter populations persisted in vineyards and conventional citrus through much of 2016, declining to undetectable levels in 2017 and 2018. Sharpshooter populations in organic citrus persisted in 2017 and 2018. From spring of 2016 to fall of 2018, glassy-winged sharpshooter adults were collected (if present) from 4 vineyards, 2 conventional citrus orchards, and 2 organic citrus orchards and subjected to quantitative polymerase chain reaction to determine if Xylella fastididosa was present in mouthparts. In conjunction, leaf samples were collected from systemically infected grapevines every three weeks from two vineyards to quantify seasonal changes in X. fastidiosa abundance in plants. In 2016, glassy-winged sharpshooters testing positive for X. fastidiosa were first observed in July and the percentage of sharpshooters positive for X. fastidiosa increased through the summer. A low percentage of petiole samples collected from chronically infected grapevine tested positive for X. fastidiosa in May, with the percentage testing positive peaking in August/September. No sharpshooters were collected from vineyards in 2017 and 2018. In vineyards, the period during which glassy-winged sharpshooters appear most likely to transmit X. fastidiosa is between July and September.