Formation of Apothecia by Sclerotia of Sclerotinia trifoliorum and Infection of Crimson Clover in the Field. R. G. Pratt, Research Plant Pathologist, Agricultural Research Service, U.S. Department of Agriculture, and Departments of Plant Pathology and Weed Science and of Agronomy, Mississippi State University, Mississippi State 39762. W. E. Knight, Research Agronomist, Agricultural Research Service, U.S. Department of Agriculture, and Departments of Plant Pathology and Weed Science and of Agronomy, Mississippi State University, Mississippi State 39762. Plant Dis. 66:1021-1023. Accepted for publication 8 February 1982. 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, 1982. DOI: 10.1094/PD-66-1021.

Sclerotia of Sclerotinia trifoliorum, collected in the field and produced in culture, were added to soil beneath fall-planted crimson clover in Mississippi during three growing seasons. Apothecia developed most frequently during December from sclerotia collected in the field, stored air-dry for 6–7 mo at 25 and 36 C, and buried at ≤1 cm in September and October. Fewer apothecia developed from sclerotia stored at 4 C, buried at ≥3 cm, or added to soil after October. Apothecia rarely developed from sclerotia produced in culture. Disease patches appeared from January to March and reached maximum sizes by April. Sizes were correlated with numbers of apothecia previously observed.

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