爵床的甲醇提取物对小菜蛾的生物活性作用

为探明爵床(Justicia procumbens)甲醇提取物对小菜蛾的生物活性,采用室内生测法测定了爵床甲醇提取物对小菜蛾的触杀、拒食、胃毒、生长发育抑制和产卵忌避作用。结果表明,爵床甲醇提取物对小菜蛾幼虫具有较强的触杀、拒食、胃毒和生长发育抑制活性,对小菜蛾成虫具有较强的产卵忌避活性。在触杀试验中,药后1、2 d和3 d爵床甲醇提取物对小菜蛾3龄幼虫的致死中浓度(LC50)分别为5.17、4.05和3.06 mg/m L;在拒食试验中,药后1 d和2 d提取物对3龄幼虫的选择性拒食中浓度(AFC50)分别为2.64和3.13 mg/m L,药后1 d和2 d提取物对3龄幼虫的非选择性拒食中浓度(AFC50)分别为3.70、4.54 mg/m L;在胃毒试验中,药后4、5、6 d和7 d提取物对3龄幼虫的致死中浓度(LC50)分别为8.13、3.65、2.88、2.23 mg/m L;在生长发育抑制试验中,药后1 d和2 d提取物对3龄幼虫的抑制中浓度(IC50)分别为2.02、1.40 mg/m L;在产卵忌避试验中,药后1、2 d和3 d提取物对小菜蛾成虫的选择性产卵忌避中浓度(AOC50)分别为2.61、3.66、4.58 mg/m L,药后1、2和3 d提取物对小菜蛾成虫的非选择性产卵忌避中浓度(AOC50)分别为3.19、4.52、5.65 mg/m L。由此证实,爵床提取物对小菜蛾具有显著的毒杀活性,具有开发为新型高效、低毒植物源农药的潜在价值。

Bioactivity of methanol extracts from Justicia procumbens against Plutella xylostella

Plants are a treasure trove of bioactive compounds and research into the bioactivity of naturally occurring botanical compounds is an effective way to develop new pesticides. Pesticides can have many effects upon target organisms, including stomach poisoning, contact poisoning, systemic poisoning, fumigant poisoning, antifeeding and repelling activity, and growth regulation. Justicia procumbens is a traditional Chinese herbal medicine, and studies have shown that extracts from J. procumbens have insecticidal and antimicrobial activity. Plutella xylostella is an important agricultural pest of cruciferous vegetables in south China that, as it causes damage throughout the year, is responsible for huge economic losses. We used greenhouse bioassays to test the contact poisoning, antifeeding, stomach poisoning, growth regulating and oviposition-repelling effects of methanol extracts from J. procumbens against P. xylostella..Results showed that methanol extracts from J. procumbens had strong contact toxicity to P. xylostella, and that this activity was positively correlated to the concentration of the extracts. The LC₅₀ values of methanol extracts against 3rd instar larvae of P. xylostella were 5.17, 4.05 and 3.06 mg/mL within 1, 2 and 3 d after treatment, respectively. Methanol extracts from J. procumbens had significant antifeedant activity against P. xylostella, whose antifeeding rate was positively correlated to the concentration of extracts. The effect of the extracts on selective antifeeding rates was stronger than on non-selective antifeeding rates, and the antifeedant effects were decreased noticeably over time: the AFC₅₀ values were 2.64 and 3.13 mg/mL within 1 and 2 d after treatment under the selective conditions, and 3.70 and 4.54 mg/mL under the non-selective conditions. Methanol extracts from J. procumbens had strong stomach toxicity to P. xylostella, and the larval mortality was positively correlated with the concentration of the extracts and the time after treatment. In all treatments, no larvae died within 1 d after treatment. The mortality of larvae in the high concentration (32 mg/mL) treatment was 16.67% within 2 d after treatment and 46.67% within 3 d after treatment. The LC₅₀ values of methanol extracts against the 3rd instar larvae of P. xylostella were 8.13, 3.65, 2.88 and 2.23 mg/mL within 4, 5, 6 and 7 d after treatment, respectively. Methanol extracts from J. procumbens had a significant dose-dependent inhibitory effect on the larval growth of P. xylostella. Larval body mass significantly decreased in all treatments of methanol extracts compared with control, and the magnitude of the decrease correlated with the extract concentration. The IC₅₀ values of methanol extracts against the 3rd instar larvae of P. xylostella were 2.02 and 1.40 mg/mL within 1 and 2 d after treatment. Methanol extracts from J. procumbens had significant dose-dependent repelling effect on the adult oviposition of P. xylostella. There was a significant reduction in the number of eggs laid per female adult with an increasing concentration of extracts. At the same time, the oviposition repelling rate of extracts at all concentrations decreased with time, and the effect on selective repelling rates was stronger than on non-selective repelling rates. The AOC₅₀ values were 2.61, 3.66 and 4.58 mg/mL within 1, 2 and 3 d after treatment under the selective conditions, respectively, and 3.19, 4.52 and 5.65 mg/mL under the non-selective conditions. The results suggested that methanol extracts from J. procumbens have significant insecticidal activity against P. xylostella, and have the potential to be developed into a new style of botanical pesticide with high efficacy and low non-target toxicity.