Outbreak of Citrus Postbloom Fruit Drop Caused by Colletotrichum gloeosporioides in Florida.. R. T. McMillan, Jr., University of Florida, Tropical Research and Education Center, Homestead 33031. L. W. Timmer, University of Florida, Citrus Research and Education Center, Lake Alfred 33850. Plant Dis. 73:81. Accepted for publication 4 November 1988. Copyright 1989 The American Phytopathological Society. DOI: 10.1094/PD-73-0081A.
Necrotic lesions on petals, blossom blight, and fruit abscission followed by persistent calyxes were first observed on Tahiti lime (Citrus latifolia Tan.) in Collier County, Florida, in 1983. Symptoms were similar to postbloom fruit drop of citrus, first described in Belize and later in several Central and South American countries. The disease is caused by a strain of Colletotrichum gloeosporioides (Penz.) Sacc (1). In 1987, the disease was found in many orange (C.sinensis (L.) Osb.) orchards in south Florida, and by 1988 it was common south of Highlands County and present in scattered locations throughout the state. C. gloeosporioides, producing acervuli with one-celled conidia and black setae, was consistently isolated from affected petals and pedunchles of limes and oranges in Florida and produced necrotic lesions and blight of inoculated, detached blossoms of lime and sweet orange. On potted lime plants, the fungus caused blossom blight, fruit abscission, and persistent calyxes, thus reproducing field symptoms. This is the first report of postbloom fruit drop in the United States.