Effect of Some Fungicides on Causal Agent of Sclerotinia Stem Rot Disease of Rapeseed in Mazandaran Province.

Stem rot caused by Sclerotinia sclerotiorum, is one of the important diseases of rapeseed, and fungicides are applied for its control. In Iran, carbendazim and tebuconazole are often used for chemical control of the disease. In order to introduce other effective fungicides against the disease, seven fungicides were studied in laboratory conditions and then six of them were applied in the field. In the laboratory conditions, different concentrations of the fungicides showed significant differences (P<0.01) with control (without fungicide) and caused inhibition of pathogen radial growth on potato dextrose agar medium except chlorothalonil (Daconil®). Effective concentration (EC50) and minimum inhibitory concentration (MIC) of the fungicides including iprodione + carbendazim (Rovral TS®), propiconazole (Tilt®), thiophanate methyle (Topsin M®), trifloxystrobin+ tebuconazole (Nativo®), tebuconazole (Folicure®) and spiroxamine+ tebuconazole+ triadimenol (Falcon®) was calculated. The EC50 values of these fungicides were 0.10, 0.11, 0.12, 0.22, 0.36 and 0.60 ppm, and MIC values were 1, 5, 1, 10, 10 and 10 ppm respectively. In the field conditions, all fungicides, had significant difference (P<0.01) with control  and decreased the rate of the disease infection and increased the crop yield about 300 to 700 Kg/ha. Nativo® was the most effective fungicide. The duration of plant protection in Nativo® treatment was longer and occurrence of disease symptoms after spraying was later than other treatments. Therefore, these fungicides can be used in rotation with common fungicides.