Sclerotinia sclerotiorum (Lib.), the casual agent of Sclerotinia stem rot, is one of the most important pathogen of Brassica napus in north of Iran. In this study, 13 MCGs of the fungus were identified between 31 isolates of the fungus sampled from four regions of Mazandaran province, Iran. Effective fungicides are useful in integrated management of the disease. So, the effect of Tebuconazole, Propiconazole, Cyproconazole and Rovral Ts at five doses (0.0001, 0.001, 0.01, 0.1 and 1 ppm) was studied on growth inhibition of S. sclerotiorum. The results exhibited the maximum inhibition (100%) of S. sclerotiorum mycelial growth was obtained by highest dose (1 ppm) of all tested fungicides, as well as by the doses of 0.1 and 0.01 ppm of Propiconazole, Cyproconazole and Tebuconazole. In this investigation, the reaction of S. sclerotiorum isolates belong to different MCGs was evaluated against Tebuconazole, Propiconazole, Cyproconazole and Rovral Ts at their EC50 range. The results revealed high variation of S. sclerotiorum MCGs against different fungicides; and the inhibition percentage was variable between 4.29% and 71.72%.
