Cercospora sojina, the causal agent of frogeye leaf spot (FLS) of soybean (Glycine max), can cause significant yield losses. Foliar fungicide application is a common strategy used to control FLS; however, C. sojina strains with resistance to quinone outside inhibitor (QoI) fungicides have become widespread throughout U.S. soybean production regions. Because of QoI-resistance, demethylation inhibitor (DMI) and methyl benzimidazole carbamate (MBC) fungicides have become more important in managing FLS. Baseline sensitivity assays are important to monitor any shifts in fungicide sensitivity. Sensitivity of the DMI fungicides flutriafol and tetraconazole and the MBC fungicide thiophanate methyl were established for 145 C. sojina isolates collected prior to 2001(baseline isolates) and C. sojina isolates collected from 2007 to 2012 representing 12 states. Bioassays were conducted to assess effective fungicide concentration at which 50% of mycelium growth was inhibited relative to a non-fungicide control (EC₅₀) for each isolate-fungicide combination. Baseline EC₅₀ value means for flutriafol, tetraconazole, and thiophanate methyl were 0.268, 0.153, and 0.521 μg/ml. When means of EC₅₀ values for isolates collected from 2007 to 2012 were compared to baseline sensitivity EC₅₀ means, no significant difference (P < 0.05) was observed for sensitivities to flutriafol and tetraconazole. When this same comparison was done for sensitivity to thiophanate methyl, isolates collected in 2008 and 2012 were significantly more sensitive than the baseline isolates. Overall, these findings indicate no shift towards reduced sensitivity to flutriafol, tetraconazole, and thiophanate methyl. Based on these results, continued monitoring of C. sojina population sensitivity to DMI and MBC fungicides should occur.

Cercospora sojina是大豆（Glycine max）蛙眼叶斑病 (FLS) 的病原体，可导致显着的产量损失。叶面杀菌剂施用是用于控制 FLS 的常用策略；然而，对醌外抑制剂 (QoI) 杀菌剂具有抗性的C. sojina菌株已在美国大豆生产地区广泛传播。由于 QoI 抗性，去甲基化抑制剂 (DMI) 和甲基苯并咪唑氨基甲酸酯 (MBC) 杀菌剂在管理 FLS 中变得更加重要。基线敏感性测定对于监测杀菌剂敏感性的任何变化很重要。确定了 DMI 杀菌剂氟虫唑和四康唑以及 MBC 杀菌剂甲基硫菌灵对 145 C. sojina 的敏感性2001 年之前收集的分离株（基线分离株）和2007 年至 2012 年收集的C. sojina分离株，代表 12 个州。进行生物测定以评估相对于非杀真菌剂对照(EC ₅₀ )对于每种分离物-杀真菌剂组合抑制50%菌丝体生长的有效杀真菌剂浓度。氟虫唑、四康唑和甲基硫菌灵的基线 EC ₅₀值平均值为 0.268、0.153 和 0.521 μg/ml。将2007 年至 2012 年收集的分离株的 EC ₅₀平均值与基线敏感性 EC ₅₀平均值进行比较时，没有显着差异（P < 0.05) 观察到对氟三唑和四康唑的敏感性。当对甲基硫菌灵的敏感性进行同样的比较时，2008 年和 2012 年收集的分离株明显比基线分离株更敏感。总体而言，这些发现表明对氟曲唑、四康唑和甲基托布津的敏感性没有降低。基于这些结果，应继续监测C. sojina种群对 DMI 和 MBC 杀菌剂的敏感性。