Yang X B, Uphoff M D, Sanogo S
Department of Plant Pathology, Iowa State University, Ames 50011.
Plant Dis. 2001 Apr;85(4):443. doi: 10.1094/PDIS.2001.85.4.443A.
Frogeye leaf spot of soybean, caused by Cercospora sojina, is typically a disease of warm and humid regions (2). Although the disease was reported in the Midwest in the 1920s (1), no outbreaks have been recorded in Iowa. Outbreaks of frogeye leaf spot occurred during 1999 in soybean fields in Ames and Grand Junction in central Iowa. During the 2000 growing season, the disease occurred in southwestern, southcentral, central, southeastern, and east-central Iowa. Occurrences of the disease with severity (reduction of green leaf area) greater than 50% were observed in production soybean fields at Grand Junction in central Iowa and Central City in eastern Iowa. In a 12-ha no-till field planted with cv. Asgrow 2501, the disease was noticeable and uniformly distributed in the entire field in mid July. Disease severity in this field was greater than 70% by the end of August. Disease incidence, however, was less than 10% in three adjacent soybean fields. In a soybean performance test at a central Iowa location where the disease occurred in 1999 and 2000, the disease was observed on all 80 varieties, with four having a severity equal to or greater than 40%. Fourteen entries had less than a 10% disease severity and 19 entries had a disease severity equal to or greater than 30%. Infected leaves in these locations had typical lesions of frogeye leaf spot, which appeared as reddish brown margins surrounding light brown or ash gray centers. On the infected tissues, hyaline, straight, and multiseptate conidia from clustered conidiophores were found, isolated, and identified to C. sojina. The relatively warm winter temperatures in 1998 to 1999 and 1999 to 2000 were associated with frogeye leaf spot epidemics. Because of the seedborne nature of C. sojina, efforts are warranted to monitor and survey the occurrence of frogeye leaf spot in Iowa, an important seed production state in the northern soybean production region. References: (1) K. Athow and A. H. Probst. Phytopathology 42:660-662, 1952. (2) D. V. Phillips. 1999. Pages 20-21 in: Soybean Disease Compendium. Hartman et al. eds, American Phytopathological Society. St. Paul, MN.
由大豆尾孢菌引起的大豆蛙眼病，通常是温暖潮湿地区的病害（2）。尽管20世纪20年代在中西部地区报道过该病害（1），但爱荷华州尚未有疫情记录。1999年，爱荷华州中部的艾姆斯和大章克申的大豆田爆发了蛙眼病。在2000年生长季，该病害出现在爱荷华州的西南部、中南部、中部、东南部和中东部。在爱荷华州中部的大章克申和东部的中央城的生产大豆田中，观察到病害严重程度（绿叶面积减少）超过50%的情况。在一块种植Asgrow 2501品种的12公顷免耕田中，7月中旬病害明显且在整块田均匀分布。到8月底，这块田的病害严重程度超过70%。然而，相邻的三块大豆田的发病率低于10%。在爱荷华州中部一个1999年和2000年出现该病害的大豆性能测试点，在所有80个品种上都观察到了病害，其中四个品种的严重程度等于或大于40%。14个品种的病害严重程度低于10%，19个品种的病害严重程度等于或大于30%。这些地点受感染的叶片有典型的蛙眼病斑，表现为浅棕色或灰白色中心周围有红棕色边缘。在受感染组织上，发现了来自丛生分生孢子梗的透明、直且多隔的分生孢子，进行了分离并鉴定为大豆尾孢菌。1998 - 1999年和1999 - 2000年相对温暖的冬季温度与蛙眼病流行有关。由于大豆尾孢菌的种传特性，有必要对爱荷华州（北部大豆产区的一个重要种子生产州）蛙眼病的发生情况进行监测和调查。参考文献：（1）K. 阿索和A. H. 普罗布斯特。植物病理学42:660 - 662，1952年。（2）D. V. 菲利普斯。1999年。载于：《大豆病害简编》。哈特曼等人编，美国植物病理学会。明尼苏达州圣保罗。
