Integration of strobilurins and other fungicides for the control of powdery mildew on grapes

The strobilurin fungicides Amistar (azoxystrobin) and Flint (trifloxystrobin) were evaluated in 1999/00 and 2000/01 in programs that included various combinations with Thiovit (sulfur) and Topas (penconazole) for the control of powdery mildew on grapes. In most experiments the application of 6 sprays per season that included Thiovit (3 g/L) followed by various combinations of Topas (0.125 mL/L), Amistar (0.5 g/L), Flint (0.15 g/L) and Thiovit (2 g/L) controlled powdery mildew. Although strobilurins were applied from flowering to after fruit set, the order in which various fungicides were applied had little influence on the level of powdery mildew control. In experiments where the bunch or leaf area diseased was 60% or higher in unsprayed plots, the severity was less than 5% where combinations of Thiovit and Topas with either Amistar or Flint were applied. In one experiment, 3 applications of either Legend (quinoxyfen) or Prosper (spiroxamine) following 2 applications of Thiovit also provided excellent control of powdery mildew. In programs where the application of Amistar and Flint were directly compared, Flint was the most effective fungicide for controlling powdery mildew. In the experiments where downy mildew also developed, Amistar was more effective than Flint in controlling this disease.