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Epidemiology and Control of Bacterial Leaf Spot and Stem Rot of Pelargonium hortorum. D. E. Dougherty, Graduate Student, Department of Plant Pathology, The Ohio State University, Columbus 43210, Current address of senior author: Department of Plant Pathology, University of Georgia, Athens 30601; C. C. Powell(2), and P. O. Larsen(3). (2)(3)Assistant Professors, respectively, Department of Plant Pathology, The Ohio State University, Columbus 43210. Phytopathology 64:1081-1083. Accepted for publication 23 February 1974. DOI: 10.1094/Phyto-64-1081.

Xanthomonas pelargonii, the causal agent of bacterial leaf spot and stem rot of Pelargonium hortorum, was disseminated by splashing water. Leaf infection and spotting followed inoculation of Pelargonium plants with water droplets containing a suspension of the pathogen. The pathogen spread systemically from leaf spots and caused stem rot and wilting of other leaves. Wound-inoculation of Pelargonium roots resulted in infection with delayed symptoms. Cuttings removed from these plants were also infected, but were symptomless. Weekly streptomycin or fixed copper sprays delayed symptom expression, but did not prevent disease development.