Evaluation of the systemic activity of simeconazole in comparison with that of other DMI fungicides

The systemic activity of simeconazole (RS-2-(4-fluorophenyl)-1-(1H-1,2,4-triazol-1-yl)-3-trimethylsilylpropan-2-ol) in plants was compared with those of eight other sterol demethylation inhibitor (DMI) fungicides. Simeconazole prevented the infection of Blumeria graminis (DC) Speer f sp hordei Marchal on barley leaves within a radius of several centimeters from the edge of local treatment on the leaves when the compound was separated from the leaves by glass coverslips. This reveals that simeconazole has prominent vapour-phase activity. Simeconazole showed excellent curative activity against barley powdery mildew when treated 1-3 days after inoculation. Furthermore, this indicates that simeconazole has notable translaminar activity because, when the compound was applied onto either the adaxial or abaxial leaf surface, it showed excellent efficacy against powdery mildew on the opposite side of the leaf surface of barley and cucumber. Simeconazole also showed excellent efficacy against barley powdery mildew by soil drench 24h after inoculation. This suggests that simeconazole was absorbed very quickly into the barley plant after treatment. The permeability of the compound through cuticular membranes prepared from tomato fruits was about 20% at 22 h after the treatment and was much superior to that of the other DMI fungicides tested.