Acaricidal Activity of the Oleic Acid Methyl Ester from Pharbitis purpurea Seeds against Tetranychus Cinnabarinus

Acaricidal activities of the extraction of Pharbitis purpurea seeds against Tetranychus cinnabarinus were determined and fraction 8 was confirmed to be the active components. GC-MS analysis showed that fraction 8 was mainly composed of methyl oleate. Effects of the methyl oleate against Tetranychus cinnabarinus were investigated by slide-dip method and leaf-dip method. Effects of methyl oleate on the organization of Tetranychus cinnabarinus were observed by transmission electron microscope (TEM). The results revealed that the methyl oleate showed killing effects on Tetranychus cinnabarinus and inhibitory effects on the growth of the eggs. After treated with 5 mg/mL methyl oleate for 24 h, the corrected mortalities of Tetranychus cinnabarinus and eggs were 73.68% and 76.16 %, respectively, and the LC50 values were 1.1671 mg/mL and 0.9533 mg/mL, respectively. The inhibitory rates of eggs of Tetranychus cinnabarinus were 78.46%. TEM observation showed that the skin structure, muscle fiber, nuclear membrane, mitochondria, and endoplasmic reticulum of mites were damaged to varying degrees by the methyl oleate. Thus, the methyl oleate from the extraction of Pharbitis purpurea seeds showed a high acaricidal activity, and provided a theoretical basis for the development of botanical acaricides.