Increasing soil temperature to reduce sclerotial viability of Sclerotium cepivorum in New Zealand soils

A preliminary laboratory-based trial indicated Sclerotium cepivorum sclerotial viability could be reduced from >96–10.7% after 28 d at 20°C and to 0% after 16 d at 30°C. Soil solarisation significantly reduced S. cepivorum sclerotial viability in two separate trials in Canterbury (Wakanui silt loam soil), New Zealand (to 40.2 and 53.3%, respectively) when soil was covered with clear 50 μm thick polythene for 4 weeks. Sclerotial viability further decreased in two New Zealand sites; Canterbury (to 8.7%) and Blenheim (shallow silt loam soil) (to 0%) when the soil was solarised for an 8 week period. Solarisation increased the soil temperature by 6–7°C in Canterbury, although the highest temperatures were recorded in Blenheim. Microorganisms isolated from the recovered sclerotia included species of Trichoderma, Verticillium, Fusarium, Mucor, Aspergillus and four unidentified bacterial species.