Fungicide application on soybean plants based on the detection of Phakopsora pachyrhizi uredospores

In order to establish the adequate timing of fungicide application in the management of Asian soybean rust (ASR), the spraying of epoxiconazol and pyraclostrobin fungicide (EPF) was evaluated based on the detection of Phakopsora pachyrhizi (PP) uredospores in field conditions at the research farm of Faculdade Integrado de Campo Mourão, in the state of Paraná, in the crop season of 2009/2010. The experimental design was performed in randomized complete blocks with four replications composed by: 1) EPF application with humidity higher than 80%; 2-5) EPF application 1-2, 6-7, 11-12, and 18-20 days after the first detection of PP spores, respectively; 6) EPF application after the first detection of ASR symptoms; 7) EPF application in the R1 stage. Control was constituted by plants not treated with EPF. There was reduced ASR severity in all treatments. The values of the area under ASR progress curve (AUASRPC), rate of disease progress (r), and maximum severity (Ymax) in control were 520.31, 0.06, and 45.65%, respectively. The lowest values of AUASRPC (39.73), r (0.02), and Ymax (3.91%) were found in treatment 1. Nevertheless, the higher number of EPF spraying was carried out in this treatment with four applications. On the other hand, there were two applications in treatment 4. The lowest yield was recorded in control (2085 kg. ha-1). The highest yield was obtained in treatments 1, 2, 3, 4, 6, and 7, being higher than 3000 kg/ha. Furthermore, the lowest value of the thousand grain weight was estimated in control. The highest values were estimated in treatments 1, 2, 3, and 6. Therefore, the timing of fungicide application based on the detection of PP uredospores is efficient in the ASR management.

为明确杀菌剂防控亚洲大豆锈病（Asian soybean rust, ASR）的适宜施药时期，本研究于2009/2010作物季，在巴西巴拉那州坎波穆拉昂综合学院的试验农场内，以田间条件下检测到的豆薯层锈菌（Phakopsora pachyrhizi, PP）夏孢子为依据，评估了环氧菌唑·吡唑醚菌酯复配杀菌剂（EPF）的喷施效果。试验采用随机完全区组设计，设置4次重复，处理组如下：1）当田间相对湿度高于80%时喷施EPF；2-5）分别在首次检测到PP夏孢子后的1~2 d、6~7 d、11~12 d、18~20 d喷施EPF；6）首次观测到ASR症状时喷施EPF；7）大豆R1生育期喷施EPF。对照组为未喷施EPF的大豆植株。所有处理组的ASR严重度均显著降低。对照组的大豆锈病流行曲线下面积（AUASRPC）、病害流行速率（r）及最大病害严重度（Ymax）分别为520.31、0.06和45.65%。处理组1的AUASRPC（39.73）、r（0.02）及Ymax（3.91%）均为最低，但该处理共需喷施4次EPF，为施药次数最多的组别；而处理组4仅需喷施2次。对照组的籽粒产量最低，为2085 kg·ha⁻¹。处理组1、2、3、4、6、7的籽粒产量均高于3000 kg·ha⁻¹，为最高产量组。此外，对照组的千粒重最低，处理组1、2、3、6的千粒重最高。综上，基于PP夏孢子检测结果确定杀菌剂施药时期，可有效防控ASR。