New Forage Legume Hosts of Sclerotinia trifoliorum and S. sclerotiorum in the Southeastern United States. R. G. Pratt, Research Plant Pathologist, Agricultural Research Service, U. S. Department of Agriculture, Mississippi State, MS 39762. S. M. Dabney, and D. A. Mays. Assistant Professor, Department of Agronomy, Louisiana Agricultural Experiment Station, Louisiana State University Agricultural Center, Baton Rouge 70803, and Agronomist, Tennessee Valley Authority, National Fertilizer Development Center, Muscle Shoals, AL 35660. Plant Dis. 72:593-596. Accepted for publication 1 February 1988. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1988. DOI: 10.1094/PD-72-0593.

Symptoms of Sclerotinia crown and stem rot and sclerotia of Sclerotinia spp. were observed on winter pea (Pisum sativum var. arvense), caleypea (Lathyrus hirsutus), bigflower vetch (Vicia grandiflora), and hairy vetch (V. villosa) in Louisiana, Alabama, and Mississippi. Eighteen Sclerotinia isolates, obtained from three to five sclerotia from each host, were compared for morphology and pathogenicity. All isolates corresponded to S. trifoliorum or S. sclerotiorum in anamorphic features. Apothecia developed from field-collected sclerotia from winter pea and hairy vetch and from sclerotia produced in single or paired cultures by 11 isolates from the four hosts. These were identified as S. trifoliorum and S. sclerotiorum according to the size and nuclear condition of ascospores. Pathogenicity of the 18 isolates from the four legumes was demonstrated by inoculating stem tips of plants 2–3 wk old. Isolates did not differ consistently in virulence, and one or more from each host killed or severely damaged plants within 2 wk. All isolates were reisolated from necrotic inoculated stems. These results document the occurrence of diseases caused by S. trifoliorum on winter pea and hairy vetch, and S. sclerotiorum on hairy vetch, bigflower vetch, and caleypea, for the first time in North America. The potential for damage by Sclerotinia diseases in these species, as previously recognized for annual clovers, is a factor that should be considered in recommending them as winter cover crops for the southeastern United States.