Cioni F.,BETA |
Collina M.,University of Bologna |
Maines G.,BETA |
Khan M.F.R.,North Dakota State University |
And 3 more authors.
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 "calendar" 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 €/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 μg/ml. The percentage of isolates collected in 2010 with EC50 values >1 for tetraconazole was 44 %, for difenoconazole 84 %, for pyraclostrobin 27 % and for trifloxystrobin 34 %. For isolates with EC50 values >1 μg/ml, the range of EC50 values (μg/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. © 2013 Society for Sugar Research & Promotion. Source
Cioni F.,BETA |
Weeds left in beet crops can make harvesting more difficult and costly, interfere with clamping and affect processing if taken into the factory. Mature weeds shed seed to add to the soil bank and germinate in subsequent crops. Most importantly, severe yield penalties can result from a failure to control weeds. In the last three decades, herbicide and weed control developments have made a significant contribution to the increase of average sugar beet yields. In the 1990s, the reduced use of herbicides has become a necessity in order to limit environmental pollution and to safeguard human health. As a consequence, in the last years, the general trend of the crop is to achieve a gradual reduction in doses applied in pre and post-emergence by using several blends of products to valorize their synergy effects. The reduction of the use of herbicides can be obtained replacing herbicide treatments with revaluation of agronomic techniques and minimizing the dose rate of herbicides. In this way weed control involve chemical and non-chemical strategies in the integrated weed management. This system offers the potential to reduce but not to replace the use of herbicides in sugar beets on larger scale basis. © 2011 Society for Sugar Research & Promotion. Source