The Studies On Biological Characters Of Peries Rapae L. And Screening And Bioactivity Of Insecticidal Plants Against Peries Rapae L.

Through experiment and observation as well as collecting and investigating materials, we studied the biological characters of Peris rapae L. A new quick method was built to distinguish the insects of different instar larvas. We summarized its harmfulness and generating rules, came up with a tactics to biocontrol the pest.We tested 25 kinds of poisonous plant species against Peris rapae L. for poison and antifeedant activity. Stellera chamaijasme L. and Croton tiglium L. have been found appearing the best toxicity. On that base, we extracted from the two plants with several different solvents and found the ethanol extract has higher extract rates and toxic activity. Then we made gradient extraction from the anhydrous ethanol extract of the two plants with different solvents. The result showed that the n-hexane extract had significant stronger poison and antifeedant activity against Peris rapae. When diluted the n-hexane extract of the two plants at a concentration of 100 times dilution respectively, the death rates of insects in 72h reached as high as 91.7% and 84.4%, the average antifeedant rates reached as high as 79.2 %and 75.0%. LD50 reached to 2.26× 103ppm, 2.31 ×103ppm. AFC50 reached to 2.03×103ppm, 2.42×103ppm. Finally we drew an elementary conclusion that the fairly strong poisonous components in the two plants were mainly non- polar or weak-polar substance.