Khan J, Del Río L E, Nelson R, Khan M F R
Department of Plant Pathology, North Dakota State University, Fargo 58105.
North Dakota State University and University of Minnesota.
Plant Dis. 2007 Sep;91(9):1105-1108. doi: 10.1094/PDIS-91-9-1105.
Management of Cercospora leaf spot, caused by Cercospora beticola, is necessary for the economic production of sugar beet (Beta vulgaris). The objectives of this study were to evaluate the impact of two relative humidity thresholds (87 and 90%) on the daily infection values (DIVs) used to determine when fungicide applications were required, to determine whether current Cercospora management recommendations for northern areas of Minnesota and North Dakota could be used by growers in the southern areas of these states, and to compare the utility of calendar-based fungicide applications with the Cercospora management model. Research was conducted in Breckenridge, MN and St. Thomas, ND in 2003 and 2004. Fungicide applications significantly (P = 0.05) reduced maximum disease severity (y) and area under the disease progress curve (AUDPC) when compared with the nontreated control at both locations during 2003 and 2004. Fungicides applied according to DIVs calculated at RH ≥ 87% or RH > 90% gave similar results. The mandatory second fungicide application 14 days after the first application for southern areas did not significantly decrease disease severity or AUDPC, or improve root yield or recoverable sucrose compared with treatments without the mandatory application. This research illustrates that a DIV calculated at RH ≥ 87% would result in similar timing of fungicide applications compared with DIVs calculated at RH > 90%. The results further show that the recommendation of fungicide applications at initial symptom and subsequent applications based on DIV and disease severity should be used for both northern and southern growers. Finally, this research showed that fungicide applications based on the Cercospora management model provided similar, effective disease control with fewer fungicide applications compared with calendar-based applications.
对于甜菜（Beta vulgaris）的经济生产而言，由甜菜尾孢菌（Cercospora beticola）引起的尾孢叶斑病的管理至关重要。本研究的目的是评估两个相对湿度阈值（87%和90%）对用于确定何时需要施用杀菌剂的每日感染值（DIVs）的影响，确定明尼苏达州北部和北达科他州北部当前针对尾孢叶斑病的管理建议是否可供这些州南部的种植者使用，并比较基于日历的杀菌剂施用与尾孢叶斑病管理模型的效用。2003年和2004年在明尼苏达州的布雷肯里奇和北达科他州的圣托马斯开展了研究。与2003年和2004年两个地点的未处理对照相比，施用杀菌剂显著（P = 0.05）降低了最大病害严重度（y）和病害进展曲线下面积（AUDPC）。根据相对湿度≥87%或相对湿度>90%计算的DIVs施用杀菌剂得到了相似的结果。与没有强制施用的处理相比，南部地区在首次施用后14天强制进行的第二次杀菌剂施用并没有显著降低病害严重度或AUDPC，也没有提高根产量或可回收蔗糖含量。本研究表明，与相对湿度>90%计算的DIVs相比，相对湿度≥87%计算的DIVs会导致杀菌剂施用时间相似。结果还进一步表明，针对北部和南部种植者都应采用在初始症状时施用杀菌剂以及随后根据DIV和病害严重度进行施用的建议。最后，本研究表明，与基于日历的施用相比，基于尾孢叶斑病管理模型的杀菌剂施用在减少杀菌剂施用次数的情况下提供了相似且有效的病害防治效果。
