Investigating the sensitivity of Venturia inaequalis isolates to difenoconazole and pyraclostrobin in apple orchards in China

Abstract The resistance level of 90 single lesion conidial isolates Venturia inaequalis collected from multiple commercial orchards in Shaanxi and Gansu Provinces Xinjiang Autonomous Region China to the demethylation inhibitor (DMI) fungicide difenoconazole quinone outside (QoI) pyraclostrobin was examined. EC 50 values ranged 0.143 6.735 ?g/mL 0.084 2.026 ?g/mL, respectively. Among isolates, 19 had resistance, 66 reduced sensitivity, five sensitivity difenoconazole; eight 81 one pyraclostrobin. Although a weak correlation between detected, four were identified as resistant However, with practical not found widely our study only sporadic few places, indicating that at present, are still safe for disease management apple-growing areas Shaanxi, Xinjiang. risk should be managed caution, yearly monitoring development is necessary.