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

A preliminary laboratory-based trial indicated Sclerotium cepivorum sclerot ial viability could be reduced from >96-10.7% after 28 d at 20 degreesC and to 0% after 16 d at 30 degreesC. Soil solarisation significantly reduced S . cepivorum sclerotial viability in two separate trials in Canterbury (Waka nui silt loam soil), New Zealand (to 40.2 and 53.3%, respectively) when soi l was covered with clear 50 mum thick polythene for 4 weeks. Sclerotial via bility 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 degree sC in Canterbury, although the highest temperatures were recorded in Blenhe im. Microorganisms isolated from the recovered sclerotia included species o f Trichoderma, Verticillium. Fusarium, Mucor, Aspergillus and four unidenti fied bacterial species. (C) 2001 Elsevier Science Ltd. All rights reserved.