First Report of Sclerotium rolfsii on Perennial Peanut in Florida. R. L. Stanley, University of Florida, North Florida Research and Education Center, Quincy 32351. F. M. Shokes, and D. A. Berger, University of Florida, North Florida Research and Education Center, Quincy 32351. Plant Dis. 80:105. Accepted for publication 14 November 1995. Copyright 1996 The American Phytopathological Society. DOI: 10.1094/PD-80-0105E.
Rhizoma peanut (Arachis glabrata Benth.) is a warm-season perennial forage adapted to the sandy, droughty soils of the southeastern U.S., generally for locations below 31 to 32 latitude. Two cultivars (Arbrook and Florigraze) have been released for commercial production. No reports of Sclerotium rolfsii on rhizoma peanut have been found. In 1992, plots of Arbrook at the North Florida Research and Education Center, Quincy, showed symptoms of blight with a fluffy fungal growth resembling the southern stem rot that occurs on Arachis hypogaea L. No symptoms were evident on adjacent plots of Florigraze. Isolations from several stems resulted in recovery of S. rolfsii that produced characteristic rapidly growing white mycelia and brown sclerotia. Twenty individual plants from healthy plots of both cultivars were placed in fieldxsoil in 15.2 cm pots and grown in the greenhouse. None of the plants had any symptoms of disease after 4 weeks of growth. Ten plants of each cultivar were inoculated with the pathogen and 10 were kept as uninoculated checks. Plants were inoculated with 1-cm disks of potato-dextrose agar with a germinated Sclerotium and actively growing mycelium. Agar disks were placed on the crown area of plants at the soil line and plants were placed in a plastic bag for 48 h to retain moisture and allow disease development. Inoculated plants had characteristic symptoms of blight with dead or dying stems after 1 week and none of the check plants had any symptoms. The pathogen was recovered from infected plants. The experiment was completed twice. Both Arbrook and Florigraze proved to be equally susceptible when inoculated with 5. rolfsii in the greenhouse. Although the disease was severe on infected plants in field plots of Arbrook, the incidence was low and the disease disappeared without severely depleting the plant population. Therefore, this disease is not expected to have a significant impact on plantings of perennial peanut.