Sensitivity of Cercospora beticola populations in Turkey to flutriafol, mancozeb, and fentin acetate

The sensitivity of sugar beet leaf spot disease caused by Cercospora beticola to fungicides used in Turkey was determined using amycelial growth assay in petri dishes with 100 fungal isolates. The isolates were obtained fromsamples collected from 6 sugar beet production areas in 2005 and 2006. Flutriafol, mancozeb, and fentin acetate were added to Aspergillus completemedium(ACM) at the rates of 0.0, 0.05, 0.1, 0.5, 1.0, 5.0, and 10.0 μgmL^-1, and thenmycelial growth wasmeasured. ED50 values of flutriafol for all the isolates fromthe sugar beet production areas ranged from0.04 to 10.0 μg mL^-1. Tolerance to this fungicide was very high in 2 regions (Adapazarı and Çarşamba) where the disease is very prevalent due to climatic conditions. In these 2 areas 74.1%, 55.5%, 81.2%, and 68.7% of the isolates grew with 5 and 10 μg mL^-1 of flutriafol, respectively (1 μg mL^-1 flutriafol is considered inhibitory to the growth of the fungus). In the other 4 regions included in the study, tolerance was not as high. Tolerance to mancozeb developed in all the regions; however, the percentage of tolerant isolates was lowest in Çarşamba (6%) and highest in Susurluk (47.3%). Tolerance to fentin acetate varied according to the criteria used for evaluation.