SIDE-EFFECTS OF PROPICONAZOLE (TILT 250 EC) ON NONTARGET SOIL FUNGI IN A FIELD TRIAL COMPARED WITH NATURAL STRESS EFFECTS

The present study was performed as a dose-response field experiment using a trade marked formulation of the ergosterol biosynthesis inhibiting fungicide, propiconazole, applied at the recommended and ten times the recommended application rates. The soil dilution plate method was used to isolate fungi from 0-1 and 1-2 cm soil depth. Soil samples were taken 10 times during the period from May 22 to August 11, 1986. The numbers of yeasts and filamentous fungi were enumerated, the latter including Cladosporium and Penicillium, which were also enumerated separately. The fluctuations in fungal occurrence due to the propiconazole treatment were smaller than seasonal fluctuations, these most likely being caused by variations in the soil matric potential and by soil invasion of phyllosphere fungi. Fungicide treatment had significant inhibitory effects on the filamentous fungi, especially on the Cladosporium, whereas no significant effects were found on the yeasts and on Penicillium spp. From an ecotoxicological point of view, it is important that the effects were considerably delayed, with respect to the time of fungicide application.