Factors influencing survival of sclerotia of Sclerotium cepivorum in New Zealand soils

The influence of soil type, location, and sclerotial condition on survival of sclerotia of Sclerotium cepivorum Berk, was examined under field conditions. There was no significant difference in sclerotial survival in the two soil types tested (Patumahoe clay loam and Wakanui silt loam). Experiments were conducted at two locations (Auckland and Lincoln, New Zealand), which differed substantially in both average soil temperature and rainfall. Location had little effect on sclerotial survival over time. The condition of the sclerotia, related to structural damage caused by desiccation and re-wetting in the field, was an important influence on survival. A significant proportion of sclerotia (40-60%) decayed after just 2 months in soil, after which numbers declined slowly over a period of 2 years. The sudden drop in viability over the first few months in soil was attributed to damage caused by adverse environmental conditions and subsequent attack by microbes.