This study is focused on the evaluation of the efficacy of conventional fungicides against Cercospora leaf spot (CLS) on sugar beet. The results showed that the best protection against CLS was achieved by treatment with kresoxim-methyl + epoxiconazole (T1) and tetraconazole (T2). The second highest fungicide efficacy was detected after treatment with (kresoxim-methyl + epoxiconazole -T1) + difenoconazole -T2, followed by (azoxystrobin + cyproconazole) + difenoconazole, (prochloraz + propiconazole) + tetraconazole, Urtica dioica plant extracts + Salix spp. plant extracts, (trifloxystrobin + cyproconazole) + tetraconazole, and picoxystrobin + tetraconazole. The positive effect of fungicide protection on yield and sugar content was higher in the year with a higher occurrence of CLS. Good CLS management could increase the root yield by up to 19.34%, and sugar yield by up to 23.83% in comparison to the untreated check. The highest sugar yield was achieved in the treatment by (prochloraz + propiconazole) + tetraconazole, followed by (kresoxim-methyl + epoxiconazole) + difenoconazole, (azoxystrobin + cyproconazole) + difenoconazole, (trifloxystrobin + cyproconazole) + tetraconazole, picoxystrobin + tetraconazole, and Urtica dioica plant extracts + Salix spp. plant extracts. The results showed a strong relationship of root yield and sugar yield on fungicide treatment during the vegetation. The occurrence of fungicide resistance in Cercospora beticola population has an important impact on efficacy of applied fungicides in field conditions. The highest economic effectiveness coefficient was achieved at treatment by (prochloraz + propiconazole) + tetraconazole.
