In Brazil, Sclerotinia stem rot (SSR) control in soybean depends primarily on application of the fungicides carbendazim, fluazinam, and procymidone. While these fungicides can provide effective control of the disease, their protection period, which is crucial for timing their optimal application, is poorly understood. In the present study, the protection period of carbendazim, fluazinam and procymidone was determined using a detached leaf bioassay (DLB) and chromatography. For the DLB, soybean plants were treated twice with each fungicide with or without mineral oil as adjuvant; leaves were collected at two or three-day intervals from 11 to 23 days, inoculated with Sclerotinia sclerotiorum mycelium, and the necrotic area was assessed 48 h after inoculation. For the chromatography test, each fungicide was applied and the leaves were collected every two days after treatment for 14 days. Fungicide residue concentration in tissue was determined according to a modified version of the quick, easy, cheap, effective, rugged and safe (QuEChERS) method. At 5, 7, and 9 days after the first application, fluazinam, carbendazim and procymidone, respectively, had no protective effect even when applied with mineral oil. Greater control efficacy was achieved after a second application. Fluazinam showed protective activity up to 4 days while carbendazim and procymidone showed about 10 days. The mineral oil only enhanced protection activity of procymidone in the second application. The analytical chemical separation indicated that the relative concentration of fluazinam decreased at a faster rate than that of carbendazim and procymidone. At day 14, the concentration of carbendazim and procymidone decreased from 34.97 to 9.39 mg kg⁻¹, and 58.98 to 11.22 mg kg⁻¹, respectively, suggesting that 10–14 days represent the approximate timing in spacing two consecutive applications. The knowledge of the protection period of these fungicides sets the basis to improving their timing of applications.

在巴西，对大豆菌核病的茎腐病（SSR）的控制主要取决于多菌灵，多菌灵和嘧啶酮等杀真菌剂的应用。尽管这些杀真菌剂可以有效控制疾病，但对其保护时间（对确定其最佳应用时间至关重要）的保护期知之甚少。在本研究中，使用离体叶片生物测定法（DLB）和色谱法确定了多菌灵，氟喹嗪和嘧啶酮的保护期。对于DLB，将大豆植物在每种杀菌剂的处理下加或不加矿物油作为佐剂处理两次。从11到23天间隔两到三天收集叶子，接种核盘菌核盘菌（Sclerotia sclerotiorum）接种48小时后评估菌丝体和坏死区域。对于色谱测试，施用每种杀菌剂，处理14天后每两天收集一次叶子。根据快速，简便，廉价，有效，坚固和安全（QuEChERS）方法的改进版本确定组织中杀菌剂残留的浓度。初次施用后第5、7和9天，即使与矿物油一起施用，氟他南，多菌灵和嘧啶酮也没有保护作用。第二次施用后获得了更大的防治功效。氟他南显示出长达4天的保护活性，而多菌灵和嘧啶酮显示约10天。在第二种应用中，矿物油仅增强了嘧啶酮的保护活性。分析化学分离结果表明，氟菌胺的相对浓度下降速度比多菌灵和嘧啶酮的下降速度更快。在第14天，多菌灵和嘧啶酮的浓度从34.97毫克/千克降低至9.39毫克/千克^-1和58.98至11.22 mg kg ^-1，表明10-14天代表间隔两次连续施用的大概时间。这些杀真菌剂的保护期知识为改善其应用时机奠定了基础。