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Oral: Bacterial Disease Management


Epidemiology and management of bacterial leaf spot caused by novel Pseudomonas syringae strains on watermelon in Florida
E. NEWBERRY (1), L. Ritchie (1), B. Babu (1), T. Sanchez (2), K. Beckham (2), J. Jones (2), J. Freeman (1), N. Dufault (2), M. Paret (1) (1) NFREC, University of Florida, U.S.A.; (2) Department of Plant Pathology, University of Florida, U.S.A.

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Major disease outbreaks occurring on watermelon and squash caused by Pseudomonas syringae were widespread in Florida and Georgia during recent years. This was recognized as a new disease in the region, and affected approximately 6,500 acres of watermelon from Florida in 2013. Field trials were conducted during the 2014 and 2015 spring seasons in Quincy and Citra, FL to examine environmental conditions which may be conducive for disease progression, and to assess the efficacy of foliar application of copper with or without Ethylene bis-dithiocarbamate (ManKocide/Kocide 3000) and foliar/drip application of plant activator (Acibenzolar S-Methyl; Actigard) in managing both transplant and field level introductions of the pathogen. Pearson’s correlation coefficient indicated that disease severity from the four trials was significantly correlated with average weekly temperature and total weekly rainfall in greenhouse inoculated (-0.67, p < 0.0006; 0.51, p < 0.01) and field inoculated plots (-0.72, p < 0.001; 0.58, p < 0.01) respectively. ManKocide and Actigard foliar applications were found to significantly reduce disease development over time, as indicated by the area under the disease progress curve (p < 0.05). The results of this study indicate that temperature and rainfall are key factors in determining disease development, and ManKocide and Actigard foliar applications are highly effective in controlling the disease with 3 to 4 applications early in the spring season.