Control of loose smut (Ustilago nuda and U-tritici) infections in barley and wheat plants by foliar application of triadimefon

Foliar application of the broad-spectrum systemic fungicide triadimefon to loose smut-infected plants of wheat and barley produced a marked curative effect. Triadimefon was particularly effective when applied at the beginning of and during stem extension. In addition to reducing percentage plant infection, foliar application of this fungicide (particularly prior to flag leaf emergence) resulted in an increased proportion of infected ears which were only partially smutted. The curative effect of these early fungicide applications resulted in significant yield increases, as a consequence of increased grain number per m(2). Application of triadimefon to crops at ear emergence had no significant effect on percentage plant infection but resulted in lower levels of re-infection following artificial or natural inoculation of healthy ears, apparently as a result of a protectant effect of fungicide residues on or in the ovaries.