科研之友
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摘要
Cercospora leaf spot (CLS), caused by the fungus Cercospora beticola, is the most economically important foliar disease of sugar beets in Italy. It can be controlled with the integrated use of resistant varieties, crop practices and foliar fungicides. Environmental conditions strongly influence the activity of C. beticola in the field; they can be used to guide fungicide applications once the relationships are understood. To assist growers in application of foliar fungicides for CLS control, a predictive model, developed at the University of Minnesota and North Dakota State Universities, was evaluated under Italian conditions. The model was designed to predict the time when the infection by C. beticola was initiated based on hourly temperature and relative humidity data. CLS control is currently based on treatments scheduled using a %26quot;calendar%26quot; programme. This system recommends to start fungicide applications on a fixed date and continue regularly every 18-20 days. Three years of field trial evaluation of the CLS prediction model at several experimental sites, compared with the calendar programme, has resulted in a savings of 1.5 fungicide treatments (corresponding to 130 a,not (sic)/ha) without a significant loss of yield. To control CLS, multiple applications of the same fungicide during a growing season are unfortunately common. This practice provides the target fungus a suitable condition to evolve resistance. Sensitivity assays of C. beticola to DMI and QoI fungicides were carried out on CLS isolates collected in 2009 and 2010 in Northern Italy by the University of Bologna and North Dakota State University, respectively. CLS isolates were tested sensitivity to tetraconazole, difenoconazole, pyraclostrobin and trifloxystrobin using radial growth and spore germination assays. All samples collected in 2009 showed EC50 values for QoI ranging from 0.0008 to 0.2195 mu g/ml. The percentage of isolates collected in 2010 with EC50 values %26gt; 1 for tetraconazole was 44 %, for difenoconazole 84 %, for pyraclostrobin 27 % and for trifloxystrobin 34 %. For isolates with EC50 values %26gt; 1 mu g/ml, the range of EC50 values (mu g/ml) for tetraconazole was 3.4-70.0, for difenoconazole 2.0-69.5, for pyraclostrobin 1.5-43.6, and for trifloxystrobin 3.8-77.1, respectively.
- 出版日期2014-3
