First Report of Cylindrocladium Black Rot (C. parasiticum) on Florida Beggarweed. G. B. Padgett, Plant Pathology Department, University of Georgia, Rural Development Center, P.O. Box 1209, Tifton 31793 . T. B. Brenneman, Plant Pathology Department, University of Georgia, Rural Development Center, P.O. Box 1209, Tifton 31793 and N. E. El-Gholl, Division of Plant Industry, Gainsville, FL 32614-7100. Plant Dis. 79:539, 1995. Accepted for publication 3 April 1995. Copyright 1995 The American Phytopathological Society. DOI: 10.1094/PD-79-0539C.
Perithecia of Calonectria crotalariae (C. A. Loos) D. K. Bell & Sobers (imperfect stage Cylindrocladium parasiticum Crous, Wingfield & Alfenas) were observed on stem bases of approximately 5% of the Florida beggarweed (Desmodium tortuosum (Sw.) DC.) growing in a peanut (Arachis hypogaea L.) field (Screven County, Ga). Symptoms were chlorotic and necrotic foliage and a severely deteriorated, necrotic root system. Fungal identification was verified by microscopic examination and root isolations on potato-dextrose agar amended with 100 ppm of chloramphenicol and chlorotetracycline (APDA). To confirm pathogenicity, Florida beggarweed was seeded into steam-sterilized soil on 18 November 1993. Seedlings were inoculated 3 December 1993 by immersing roots in an aqueous suspension of microsclerotia (160 microsclerotia per ml of water) of a peanut or Florida beggarweed C. parasiticum isolate. Noninoculated seedlings served as controls. Immediately after inoculation, seedlings were transferred to 15.24-cm-diameter pots containing a sterilized soil mix (sand/peat, 2:1) and placed in a greenhouse (average 28°C). On 8 April 1994, each plant was removed from each pot, roots were washed, and root necrosis was rated as present or absent. Cylindrocladium parasiticum colonized 23 and 42% of the plants inoculated with the beggarweed and peanut isolate, respectively. Root tissue was excised, surfaced sterilized for 1.5 minutes in 0.53% sodium hypochlorite, blotted dry, and placed onto APDA. Cylindrocladium parasiticum was isolated from 100% of the inoculated root tissue. This report provides evidence of how C. parasiticum can survive in the absence of peanut.