Sensitivity of Wheat Powdery Mildew (Blumeria graminis f.sp tritici) towards Metrafenone

A monitoring study on the current sensitivity situation of wheat powdery mildew (Blumeria graminis f.sp. tritici) towards metrafenone was performed in 2009 with 2509 isolates. Airborne isolates were randomly collected in different regions of the most important European cereal growing regions. The sensitivities of the majority of isolates were comparable to the baseline sensitivity, which was determined in 2000 before market launch of the compound. Ninety-two isolates showed sensitivities outside the baseline. Eighty-four of them were classified as moderately adapted and could still be inhibited with registered rates of metrafenone in glasshouse tests under various preventive or curative conditions. Eight isolates were identified to be resistant, which were not fully inhibited at registered rates. Resistance management strategies and further extensive monitoring studies are indicated for a sustainable use of metrafenone against wheat powdery mildew.