Biocontrol of Pierce’s disease of grapevine and citrus greening with a benign strain of Xylella fastidiosa
Donald Hopkins: University of Florida
<div>Vascular diseases caused by xylem-limited <em>Xylella fastidiosa </em>subspp. and phloem-limited <em>Candidatus</em> Liberibacter spp. result in large economic losses in many agricultural plants. <em>X. fastidiosa </em> is rapidly spreading into new hosts and areas. Except for plant resistance, there is no effective control for these diseases. In a trial established in the UC Riverside vineyard in 2011, a pin-pricking technique was used to inject a benign strain of <em>X. fastidiosa</em> (EB92-1) into the xylem vessels of Pinot Noir and Cabernet Sauvignon grapevines in the greenhouse prior to transplanting into the vineyard. Under heavy disease pressure, EB92-1 has provided control of Pierce’s disease (PD) for 6 years in Cabernet Sauvignon and Pinot Noir. Compared to only 10% of the treated vines, 40 percent of the untreated vines had severe PD symptoms. None of the treated vines have died; whereas, 10% of the untreated have died. Trials were established in Florida in 2014 to evaluate EB92-1 for prevention of citrus greening symptoms. A power drill and syringe were used to inject the biocontrol strain into the tree. After 3 years, 53% of the untreated, mature trees were dead or dying from citrus greening, compared to only 10% of the treated. In young trees, there were moderate symptoms in 18% of the untreated and in 5% of the treated. Biological control of diseases caused by <em>X. fastidiosa</em>, and possibly <em>Candidatus </em>L. subspp., with a benign strain of <em>X. fastidiosa</em>, EB92-1, may be feasible.</div>
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