Efficacy of flutriafol compared to other triazole fungicides for the control of sugarcane smut

Smut is an important disease of sugarcane, caused by the fungus Sporisorium scitamineum. Two fungicides, propiconazole and triadimefon can be applied as a 5 min dip to protect the buds from smut infection. This 5 min dip of 1-2 tonne bundles of seed cane has some practical problems. The treatment requires a separate, large 5 000-10 000 L tank and disposal of the waste fungicide by an environmentally acceptable method is difficult and costly. The aim of this research was to evaluate the potential of flutriafol for control of smut by methods that will be more practical for field application. Two pot experiments were undertaken to: (i) determine whether flutriafol mixed with fertiliser can be taken up by sugarcane roots in sufficient concentration to protect plants from smut infection; and (ii) compare the efficacy of flutriafol with other triazole fungicides, propiconazole and triadimefon, when mixed with fertiliser or used as a dip. The pot trials also tested methods of inoculation with smut that could be used in larger-scale field trials of the fungicide. Results indicated that flutriafol is effective in significantly reducing sugarcane smut infection when applied at rates of 100-400 g a.i./ha mixed with fertiliser and at rates of 12.5 g a.i./100 L and above when applied as a 10-minute dip of setts. There were significant relationships between application rate of flutriafol and smut suppression when the fungicide was applied mixed with fertiliser. The 10-minute dip applications of the three triazole fungicides were more effective than the fungicide/fertiliser mix. Propiconazole and triadimefon were equally effective when applied as a dip, but they were less effective than flutriafol when mixed with fertiliser. Control was achieved when the smut was injected into the buds or applied by a dip of the setts at planting. Results suggest that flutriafol can kill smut fungus after it has established within the plant. Dipping setts in a suspension of smut spores is a practical method of inoculation that can be used for future field trials of flutriafol.