Abstract: In order to explore the application value of Melodinus suaveolens as biological pesticides,the leaves of M.suaveolens was extracted with methanol by cold maceration.After that,simultaneous distillation extraction (SDE) was adopted for extracting the essential oil from leaves of M.suaveolens. Leaf-tube residual bioassay and slide-dip immersion method were used respectively to detect the insecticidal activity of the methanol extract and essential oil against Gynaikothrips uzeli Zimmerman and Panonychus citri (McGregor).The results showed that the methanol extract of M.suaveolens possessed obvious insecticidal activity on G.uzeli. After 72 h treatment,the mortality rate of G.uzeli was 76.89%.The further biological activity test indicated that the insecticidal composition of M.suaveolens which against G.uzeli mainly located in the EtOAc-soluble fraction.After 24 h treatment,the value of LC₅₀ was 4.9507 mg/mL. The methanol extract and essential oil from M.suaveolens leaves showed significant toxicity against P.citri, the value of LC₅₀ were 5.5524 mg/mL and 0.4142 mg/mL after 24 h treatment,respectively.In conclusion,results of this study provided a theoretical basis for further research on the bio-active natural products of M.suaveolens against G.uzeli.

Key words: Melodinus suaveolens, essential oil, methanol extract, bioactivity