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CHARACTERIZATION OF THE CAUSAL AGENT OF POSTBLOOM FRUIT DROP OF CITRUS.. J. P. Agostini, Univ. Florida, Citrus Research and Education Center, Lake Alfred 33850; L.W. Timmer(1), and D.J. Mitchell(2). (1)Univ. Florida, Citrus Research and Education Center, Lake Alfred 33850, (2)Dept. Plant Pathology, Gainesville 32611. DOI: 10.1094/Phyto-82-607.

Postbloom fruit drop (PFD) of citrus was caused by slow-growing, orange strains of Colletotrichum gloeosporioides (C.g.) but not by fast-growing, gray strains. The colony color and morphology, conidial size and shape, setae production, growth rate, and optimum temperature for growth of the orange and gray strains of C.g. were compared to Gloeosporium limetticola, the cause of anthracnose of Key lime. The orange strain of C.g. and G. limetticola were indistinguishable on the basis of all characters examined, and the gray strain of C.g. was distinct in almost every case. In pathogenicity tests, G. limetticola produced the blossom blight symptoms of PFD similar to those produced by the orange strain of C.g.