Survival of sclerotia of Sclerotium rolfsii: Influence of sclerotial treatment and depth of burial

Abstract The influence of sclerotial treatment (drying, washing), source of sclerotia (soil or culture) and depth of burial in soil on survival of sclerotia of Sclerotium rolfsii was determined at two locations (North Carolina and Georgia) during the 1983–1984 winter and at North Carolina during the 1984–1985 winter. Survival was significantly influenced by depth of burial at both locations and by sclerotial treatment before burial. About 11–31% of the sclerotia buried deeper than 2.5cm survived after 30 days, regardless of sclerotial treatment or source of sclerotia. In contrast, 65–84% of those on the soil surface remained viable. Viability of the remaining sclerotia declined gradually during the 9 months of the experiment. Drying the sclerotia before burial significantly reduced survival. Continual washing of sclerotia in tap water for 5 h after drying and before burial further reduced survival. Reduction in viability over time with increasing depth was less for non-dried sclerotia than for those that had been dried, or dried and washed, with up to 55% survival of non-dried sclerotia after 9 months. Fewer sclerotia produced in non-sterile soil germinated after recovery from burial than those produced in culture. Non-germinating sclerotia frequently were colonized by Trichoderma spp. Soil temperature at 5, 10 and 15cm depths and %CO2 in the soil atmosphere at 5 and 15 cm were not correlated with survival. Longevity of sclerotia of S. rolfsii in soil can be reduced by drying and deep burial, both of which predispose sclerotia to colonization by soil microbes.