Sclerotinia Blight of Peanuts in Oklahoma and Occurrence of the Sexual Stage of the Pathogen1

Abstract Sclerotinia blight of peanuts was discovered in Oklahoma in 1972. The disease is caused by Sclerotinia sclerotiorum (Lib.) de Bary varieties “Minor” and “Major” Purdy (Whetzelinia sclerotiorum (Lib.) Korf & Dumont). S. sclerotiorum “Minor” is more prevalent. Sclerotinia blight has been found in seven of the 23 major peanut-producing counties in Oklahoma since its discovery and it is regarded as a major peanut disease. Both fungal varieties overwintered in the field as sclerotia and produced apothecia and ascopores from late April to early June. Peanut plants exposed to natural ascospore discharges in the field became infected with both varieties of the fungus.