EVALUATION OF METHODS FOR THE CHEMICAL CONTROL OF RHIZOCTONIA ROOT-ROT OF WHEAT

In a preliminary screening test of 14 fungicides against rhizoctonia root rot of wheat in pots, six triazole compounds were effective in reducing disease severity. Of these, triadimenol or triadimefon and flutriafol were further investigated in a series of glasshouse experiments and a small plot trial. Flutriafol at 200 g a.i. ha-1 equivalent was more effective as a soil-applied fungicide than triadimefon, but triadimenol was more effective than flutriafol as a seed-applied fungicide. In combinations as seed and soil applications, the fungicides were more effective in reducing the severity of rhizoctonia root rot when flutriafol, at either 100 g or 200 g a.i. ha-1, was mixed through the soil rather than placed in a smaller volume of soil adjacent to the seed. However, when flutriafol was placed on double superphosphate to give a rate of 100 or 200 g a.i. fungicide ha-1 adjacent to the seed it reduced disease severity and increased plant weight, with or without a triadimenol seed treatment. Similarly, in small field plots disease severity was reduced by flutriafol-amended double superphosphate at 200 g in 1988 and at 100 g and 200 g a.i. ha-1 in 1989. © 1990.