Vanda is a highly valued and important orchid in the horticultural industry; however, it is usually damaged by black rot disease, caused by Phytophthora species, leading to substantial economic losses. This study aims to evaluate multiple fungicides for black rot control. Oomycetes were isolated from diseased plants, and these isolates brought about a 100% disease incidence in Vanda with water-soaked lesions, becoming necrotic within 24 h. The isolates were identified as Phytophthora palmivora based on a phylogenetic analysis of internal transcribed spacers (ITSs) and cytochrome oxidase spacer regions. For controlling black rot disease, eight fungicides or mixtures with different target sites and modes of action were screened, including cyazofamid, dimethomorph, fosetyl-aluminum, metalaxyl, thiophanate-methyl, a mixture of fluopicolide and fosetyl-aluminum, a mixture of mancozeb and valifenalate, and a mixture of quintozene and etridiazole. All tested fungicides showed 33%–100% growth inhibition using the poisoned food technique. In greenhouse experiments, seven tested fungicide formulations, except for thiophanate-methyl, exhibited 20%–66% reduced lesion sizes compared with the no-chemical control. The information on fungicides with different filicide group codes could assist a fungicide spray program for black rot management in orchids.

万代兰是园艺界中非常有价值和重要的兰花；然而，它通常会受到疫霉属物种引起的黑腐病的损害，导致巨大的经济损失。本研究旨在评估多种用于黑腐病防治的杀菌剂。从病株中分离出卵菌，这些分离株使万代兰发病率100% ，出现水浸状病斑，24小时内坏死。基于内转录间隔区 (ITS) 和细胞色素氧化酶间隔区的系统发育分析，这些分离株被鉴定为棕榈疫霉 ( Phytophthora palmivora) 。为防治黑腐病，筛选了8种具有不同作用部位和作用方式的杀菌剂或混剂，包括氰霜唑、烯酰吗啉、乙齿铝、甲霜灵、甲基托布津、氟吡菌胺与乙齿铝复配剂、代森锰锌和代森锰锌复配剂。伐非那酯，以及五硝基苯和乙二唑的混合物。使用毒食技术，所有测试的杀菌剂均显示出 33%–100% 的生长抑制作用。在温室实验中，除甲基托布津外，七种测试的杀菌剂配方与无化学对照相比，病斑尺寸减少了 20%–66%。有关具有不同杀丝剂组代码的杀菌剂的信息可以帮助兰花黑腐病管理的杀菌剂喷雾程序。