Control of sugar beet powdery mildew with strobilurin fungicides

Powdery mildew, caused by Erysiphe betae is a major foliar disease of sugar beet in areas with dry and relatively warm weather conditions throughout the world. In the present study, four fungicides belonging to the relatively new class of strobilurin fungicides, azoxystrobin, kresoxim-methyl, pyraclostrobin and trifloxytrobin were evaluated in three different application doses (100, 150 and 200 mg a.i./ha) during 2003-2004 for the control of disease. On the results obtained can be drawn the following conclusions: Significant reduction of powdery mildew incidence in all the fungicide-treated plots compared to the untreated control plots; Trifloxystrobin and kresoxim-methyl showed better performance compared to remaining two strobilurin fungicides, azoxystrobin and pyraclostrobin that showed a poor to modest activity against the disease, during both years of the study; Differences in the level of control efficiency, obtained by several strobilurin fungicide treatments can be explained by variation in the level of intrinsic activity of each fungicide against the pathogen; The mixtures of trifloxystrobin or kresoxim-methyl with either difenoconazole or cyproconazole had excellent performance against the disease. When cyproconazole or difenoconazole were applied in mixture with azoxystrobin or pyraclostrobin, a significant improvement of control efficiency was achieved compared to the control.