The toxicity of the fungicide propiconazole to soil flagellates

We investigated the effects of the ergosterol-inhibiting fungicide, propico nazole {1-[[2-(2,4-dichlorphenyl)-4- propyl- 1,3-dioxolan-2- yl]methyl]- 1H - 1,2,4-triazole; Tilt}, on mixed natural populations of bacterivorous and fungivorous flagellates in soil and on single species of bacterivorous flag ellates in liquid culture. The fungicide affected a mixed natural populatio n of fungivorous flagellates less than the population of bacterivorous flag ellates. Our results indicated that the effects of propiconazole on flagell ates are direct toxic effects and not effects mediated via their food. All tested types of flagellates were significantly harmed when exposed to the c oncentration of propiconazole normally applied to agricultural fields (625 mg l(-1)). However, when exposed to the concentration of propiconazole whic h we expect in the soil water phase after application (ca. 0.6 mg l(-1)) th e effect on most of the tested flagellates was slight. Still, one tested fl agellate species, Dimastigella trypaniformis, was extremely sensitive to th e compound, and it is possible that field application of propiconazole has negative effects on certain sensitive species, and therefore alters the com position of the soil flagellate community in the direction of a higher r/K ratio.