EVALUATION OF BACTERICIDES AND MODES OF DELIVERY FOR MANAGING PIERCE'S DISEASE

• Author(s): Kirkpatrick, Bruce; Andersen, Peter; Civerolo, Ed; Jones, Dawna-Darjean; Purcell, Alexander; Smith, Rhonda; Vargas, Chad; Weber, Ed;
• Abstract: For the past four years we have been evaluating plant micronutrients and inducers of systemic acquired resistance as prophylactic agents to protect grapevines against infection by Xylella fastidiosa (Xf) or as therapeutic agents to cure Pierces disease (PD) affected grapevines. To date, none of the plant micronutrients containing zinc, copper or manganese or compounds that induce systemic acquired resistance in plants such as Actiguard(R), Messenger(R), or Resist(R) showed efficacy when used as prophylactic agents to prevent infection of Xf in healthy grapevines, both in field trials and, for some materials, greenhouse evaluations of materials applied to potted grapevines that were then exposed to Xf-infectious sharpshooter vectors. Evaluation of plant micronutrients and two antibiotics as therapeutic agents for curing, or at least causing a remission of symptoms in PD-affected grapevines, were more encouraging. Many of the PD-affected Merlot grapevines that were injected with zinc or streptomycin in Fall, 1999 and Spring, 2000 remained free of PD symptoms 3 years following treatment, whereas nearly all of the untreated control vines were dead. However, inspection and evaluation performed in October 2003 revealed that some of the vines that were symptomless in 2002 have now developed some early symptoms of PD. These symptoms may be the result of residual Xf populations that were not killed by the bactericide treatment finally multiplying to levels where they induced disease symptoms or these early infections may be the result of recent inoculation of treated vines by infectious-PD vectors. Field evaluation of a citrus terpene-based bactericide in Fall, 2002 did not reduce Xf populations in treated vines and all of these treated vines had progressed symptoms of PD in Fall, 2003.
• Publication Date: Aug 2003
• Journal: 2003 Pierce's Disease Research Symposium