Waltheria indica L. is a traditional officinal plant with high medicinal values. This work aims to develop a stable microemulsion of W. indica extract and study its antifungal activity against Phytophthora capsici Leonian. The results indicated that the optimal compositions of W. indica microemulsion (WIM) were 5 % crude extract of W. indica, 10 % ethyl acetate, 5 % ethanol as solvents, 5 % pesticide emulsifier 601# (601), 10 % pesticide emulsifier BY (El-40) and 65 % water, and the microemulsion presented an average particle diameter with 1047 nm, the polydispersity index was 0.19. The W. indica microemulsion (WIM) could effectively inhibit the different growth and development stages of P. capsica in vitro, and the EC₅₀ of WIM inhibit P. capsici mycelial growth and sporangium formation and zoospore production were 0.228 and 1.923 and 1.786 μg/mL and exhibited significantly protective activity against P. capsica in pot experiments. In addition, the WIM treatment caused severe destruction to the cell membrane of P. capsici that contents of the cells leaked out. The relative conductivity, N-Acetyl-D-Glucosamine (D-GlcNAc) contents, and malondialdehyde (MDA) concentration were also significantly increased after WIM treatment. Besides, WIM inhibited the activities of P. capsici antioxidant enzymes (SOD, POD, CAT), thus increased the content of hydrogen peroxide, further aggravated the damage of the membrane system. In general, these findings provided a scientific basis for WIM as a biological agent against P. capsici.

Waltheria indica L. 是一种具有很高药用价值的传统药用植物。本工作旨在开发一种稳定的籼稻提取物微乳液，并研究其对辣椒疫霉病菌的抗真菌活性。结果表明，籼稻微乳(WIM)的最佳组成为5%籼稻粗提物、10%乙酸乙酯、5%乙醇为溶剂、5%农药乳化剂601#(601)、10%农药乳化剂BY(El-40)和65%的水，微乳液的平均粒径为1047nm，多分散指数为0.19。该W.籼稻微乳液（WIM）能有效抑制的不同生长发育阶段P. capsica 在体外，WIM 抑制P. capsici菌丝生长和孢子囊形成和游动孢子产生的 EC _{50 分别}为0.228、1.923和1.786 μg/mL，在盆栽实验中对P. capsica表现出显着的保护活性。此外，WIM 处理对辣椒的细胞膜造成严重破坏，导致细胞内容物泄漏。WIM 处理后，相对电导率、N-乙酰-D-葡糖胺 (D-GlcNAc) 含量和丙二醛 (MDA) 浓度也显着增加。此外，WIM 抑制P. capsici的活性抗氧化酶（SOD、POD、CAT），从而增加过氧化氢的含量，进一步加剧了膜系统的损伤。总的来说，这些发现为 WIM 作为抗辣椒疫病菌的生物制剂提供了科学依据。