The effects of temperatures and crop mulch on topsoil in the inactivation of the sclerotia of Sclerotinia sclerotiorum were studied by oven heating in three field experiments during three months. Field experiments were performed in Piracicaba and in Brasília. Sclerotia were produced in a carrot+cornmeal medium, incorporated into the soil (oven-heating), conditioned in nylon bags, and buried in the soil at 5, 10 and 30 cm (field). The soil treatments in the field were: solarization (S), non-solarization (NS), and solarized soil added to crop mulch (PS). Sclerotia samples were collected every 30 days to observe the viability and presence of contaminants in NEON medium. The oven heating of the soil at 50 and 60º C and the use of diverse crop mulch inactivated the sclerotia, which had a higher incidence of contaminants. In the field, the effect of soil solarization was significant. The sclerotia were killed in S after 90 days at three depths in the first experiment and in PS after 60 days at 5 and 10 cm in the other two experiments. The incidence of contaminants in sclerotia in solarized soils was significantly higher in S, followed by PS; however, a greater variability of contaminants was observed in PS. Temperatures of the soil in PS were higher when compared to the other treatments at the same depth. This factor reduced the inactivating time of the sclerotia from 90 days in S, to 60 days in PS.
