Survival of Claviceps Purpurea and C. Paspali Sclerotia

SUMMARY

Claviceps purpurea sclerotia did not survive longer than 6 mo regardless of the time of year sclerotia were placed outdoors in soil in Georgia. Sclerotia were rapidly deteriorated by soil microorganisms and damaged by plant roots, mites and insects. Claviceps paspali sclerotia survived up to 12–14 mo after placement in soil in October. Sclerotia placed in soil at other times of the year survived for shorter periods. Optimal sclerotial germination occurred 6–9 mo (April-July) after placement in the field on 1 November. The germination period corresponds to the time when Paspalum spp. flower and when ergot is first seen in the field. Claviceps paspali sclerotia also were deteriorated by soil fungi and bacteria but 45–80% of the sclerotia germinated at optimal conditions. Lack of Sclerotium survival is responsible for the infrequent occurrence of Claviceps purpurea upon small grains and grasses in the southeastern USA. Sclerotia of C. paspali provide ascospore inoculum throughout the long flowering period of Paspalum spp. but it is unlikely that sclerotia survive two seasons to produce ascospores.