Preliminary Studies on the Bioactivity of Crude Extract from Mikania micrantha on Insect and Plant Pathogen

Preliminary studies on the bioactivity of crude extracts from Mikania micrantha H.B.K. on larva of Pieris rapae Plutella xylostella were conducted. The results showed that the inhibitory and antifeedant activity of crude extract from M. micrantha. against larvae of Pieris rapae and Plutella xylostella are remarkably effective. The toxicity of 500 mg·L~(-1) ethanol extract against 1～2 instar larva of Pieris rapae were 80%, LC_(50)=293.4 mg·L~(-1), while to 2～3 instar larva of Plutella xylostella were over 70%, LC_(50)=343.5 mg·L~(-1). The toxicity of ethanol extracts to these two kinds of larva are better than that of acetone extract. Antifeedant activity of 125 mg·L~(-1) of ethanol extracts are good to both larva and antifeedant ratio are 97.4% and 70.4% respectively. The antifeedant ratio of acetone extracts are 96.5% and 98.3% respectively. In 0.02 g/mL (dry substance of M. micrantha/culture medium) concentration, inhibitory effect of carbinol and ethanol extract to Phytophthora capsili Exserohilum turcicum are 100%.