Disease Note

A New Outbreak of Citrus Canker in Florida. C. L. Schoulties and J. W. Miller, Florida Department of Agriculture & Consumer Services, Gainesville 32602; R. E. Stall, University of Florida, Gainesville 32611; E. L. Civerolo, USDA-ARS, Beltsville, MD 20705; and M. Sasser, University of Delaware, Newark 19711. Plant Disease 69:361, 1985. Accepted for publication 21 January 1985. Copyright 1985 The American Phytopathological Society. DOI: 10.1094/PD-69-361f.

In August 1984, leaf spots and twig lesions were found to be widely distributed on citrus in a Florida citrus nursery.  Extensive subsequent surveys showed lesser infections in eight other nurseries.  Leaf spots were irregular to round, 3–5 mm in diameter, flat, water-soaked, often necrotic in the center, and usually surrounded by a chlorotic halo.  Water-soaked elongate lesions with necrotic centers were observed on twigs.  Symptoms were more severe on grapefruit than on other citrus.  A yellow-pigmented bacterium consistently isolated from the lesions was identified as Xanthomonas campestris pv. citri (Hasse) Dye on the basis of morphology, serology, fatty acid analysis, and pathogenicity to inoculated citrus leaves and fruit.  Extensive efforts are in progress in Florida to eradicate citrus canker.