FUNGICIDE SENSITIVITY OF POPULATIONS OF WHEAT POWDERY MILDEW (ERYSIPHE-GRAMINIS F-SP TRITICI) IN CENTRAL-EUROPE IN 1993

In 1993 we observed the sensitivity of wheat powdery mildew population s (Erysiphe graminis DC f.sp. tritici Marchal) from the Czech Republic , Austria, Hungary and Slovakia to the fungicides triadimenol, tebucon azole, propiconazole, flutriafol and fenpropimorph. The highest resist ance value was shown to triadimenol, which attained a mean resistance factor (MRF) of 29 (expressing how many times the population is more r esistant than are standard sensitive isolates) in the mildew populatio n from the Czech Republic. The mildew populations from eastern Slovaki a and eastern Hungary, populations geographically isolated from the ot her populations, showed very high sensitivity to all fungicides tested . There was most sensitivity to fenpropimorph (smallest MRF values) co mpared with the other fungicides. Cross-resistance was established amo ng all triazoles used, but not between triazoles and fenpropimorph. Se nsitivity of wheat powdery mildew populations from Central Europe to t hese fungicides is considered adequate, and the development of resista nce has shown a decreasing tendency in recent years.