Comparisons of Three Bacterial Leaf Spots of Hibiscus rosa-sinensis. A. R. Chase, Associate Professor of Plant Pathology, University of Florida, IFAS, Agricultural Research and Education Center, 2807 Binion Road, Apopka 32703. Plant Dis. 70:334-336. Accepted for publication 30 September 1985. Copyright 1986 The American Phytopathological Society. DOI: 10.1094/PD-70-334.

Three bacterial leaf spot diseases were observed on Hibiscus rosa-sinensis during the 1983–1984 season in central and southern Florida. Pseudomonas cichorii, P. syringae, and Xanthomonas campestris pv. malvacearum (X. c. malvacearum) were isolated in pairs and singly from symptomatic tissue. Lesions caused by P. cichorii that developed within 3 days of inoculation were up to 1 cm wide, irregularly shaped, and had a distinctive black border with a separate purple margin. P. cichorii was most severe on mature leaves, especially the oldest. Lesions caused by P. syringae developed 5–14 days after inoculation and were usually 1 mm wide, angular, and usually without a halo. Most lesions formed on immature leaves or those recently expanded and commonly caused distortion. Lesions caused by X. c. malvacearum formed 7–14 days after inoculation and resembled those caused by P. syringae. These lesions formed on mature leaves only and were frequently surrounded by a chlorotic halo. Leaves infected by X. c. malvacearum commonly abscised.