| Crude methanol extracts of 66 species of plants, including 38 families collected from Shiwan Mountains in Guangxi Zhuang Autonomous Region in China, were screened for toxic and antifeedant activity against Plutella xylostella (L.). Extracts of Daphniphylum calycinam Benth. and Catunaregam spinosa (Thunb.) Tirveng fruit showed more antifeedant activity against the larvae of Plutella xylostella than one's of others species, and their antifeedant rates in 24h in no-choice test reached 92.24%, 87.38% at the concentration of 10 mg-mL-1, respectively. At other experiment, the methanol extracts of Catunaregam spinosa fruit exhibited strong antifeedant as well as toxic activity against Pieris rapae (L.), the antifeedant rate in 24h was 100%, and the corrected mortality in 24h measured by immersion method reached 76.67%.The powdered fruit of Catunaregam spinosa was extracted with petroleum ether, ethyl acetate and methanol, respectively. The methanol extract showed more antifeedant activity against the larvae of Plutella xylostella and Pieris rapae than the petroleum ether extract and ethyl acetate extract, indicating the active ingredients in the fruit of Catunaregam spinosa were polar compounds in the methanol extract.The active substances of the methanol extract were isolated with liquid-liquid extraction with different solvents and precipitation separation with distilled water. The n-butyl alcohol fraction and the precipitate in the methanol/water were the most effective in antifeedant activity against the larvae of Plutella xylostella and Pieris rapae. At the concentration of 5 mg·mL-1, the antifeedant rates of the n-butyl alcohol fraction in 24h against both pests were 90.97% and 96.37%, respectively.Further separation of the n-butyl alcohol fraction was conducted with macroporous adsorption respectively resin. The adsorbent was D-101 resin and the eluants were 40%EtOH and 100%EtOH. The results of bioactivity assays showed that the 100%EtOH elution was more biologically active against Plutella xylostella than the 40%EtOH elution, and the antifeedant rate reached 86.44% at a concentration of 2.5 mg·mL-1.The active ingredients of the 100%EtOH elution were separated with silica gel column chromatography, eluting with chloroform: methanol: water (9:1:0.1,v/v). Four fractions of the eluate, namely as LS1-1, LS1-2, LS1-3, and LS1-4, were collected. The results of the bioassay-guided tests showed that the LS1 -4 was the most bioactive against the larvae of Plutella xylostella and the Pieris rapae. The antifeedant rates against both pests reached 62.68% and 60.78%, respectively, at a concentration of 1.25 mg·mL-1We observed the behaviour of the larvae of Plutella xylostella and the Pieris rapae in no-choice tests with the LS1-4 treatments to study the temporal effects of the LS1-4 on four behavioural activities, namely palpating, feeding, walking and resting. The observation period was split into three intervals, i.e., P1 (0-30min), P2 (30-90min) and P3 (90-180min). The results showed that the LS1-4 inhibited feeding and stimulated locomotion behaviour from the onset of the tests, indicating that the LS1-4 was most likely sensory mediated antifeedants and had no postingestive, toxic effects. The larvae of Plutella xylostella exposed to the LS 1 -4 significantly increased the percentage of time spent on palpating during P2 and on feeding during P3, suggesting that habituation occurred to the LS4-1.But no habituation occurred to the LS4-1 on the larvae of Pieris rapae.
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