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Disease Note

An Epidemic of Lepto Leaf Spot in Alfalfa Caused by Leptosphaerulina briosiana. D. A. Roberts, E. S. Horner, G. M. Prine, and F. A. Johnson, University of Florida Agricultural Experiment Station, Gainesville 32611. Plant Disease 68:732, 1984. Accepted for publication 4 May 1984. Copyright 1984 The American Phytopathological Society. DOI: 10.1094/PD-68-732d.

Lepto leaf spot, caused by Leptosphaerulina briosiana (Poll.) Graham & Luttrell, was unexpectedly severe in the early spring growth of alfalfa (Medicago sativa L. 'Florida 77') in five fields inspected in north central Florida in 1984.  Numerous black lesions and "eyespots" killed young leaves, which turned brown and clung to the stems.  The first crop of hay was a total loss in two fields, but a few plants remained green.  Lepto leaf spot has never before caused such extensive lossses in Florida.  The numerous pseudothecia observed in stems killed by an exceptionally hard freeze late in December 1983 provided unusually high amounts of primary inoculum, and the cool wet weather of early spring favored rapid development of disease.

Reference: Graham, J. H., and Luttrell, E. S. Phytopathology 51:680, 1961.