Cercospora beticola sensitivity to strobilurins and triazoles in Italy.

Introduction Commercial mixtures of difenoconazole, fenpropidin, tetraconazole, trifloxystrobin and azoxystrobin are the most frequent fungicides used in Italy to control cercospora leaf spot (CLS), caused by the fungus Cercospora beticola. The resistance development risk to these fungicides is moderate for triazoles and piperidines, whereas the risk is high for QoIs (Brent and Holloman, 2007). Therefore, this study was aimed to evaluate the sensitivity of C. beticola isolates collected from Northern Italy to difenoconazole and strobilurin fungicides. Material and methods Total 228 isolates were collected from trial plots, commercial fields and one garden in September 2012 and 2013 for fungicide sensitivity studies. Conidial germination tests were examined using trifloxystrobin as technical grade (Sigma) to achieve 0.01, 0.1, 1, 2 mg/L and commercial formulation of 100 mg/L (Flint, 50%, Bayer). Technical grade of difenoconazole (Sigma) (0, 0.01, 0.1, 1, 10 mg/L) was tested for mycelial growth inhibition. Mean EC50 ..........