| Over use chemical control of Plutella xylostella L.,has resulted in insecticide resistance and the destruction of the ecological environment seriously.Therefore,it is significant to research and develop on new biological pesticides to control P.xylostella.The soxlet's extraction method was used to extract the bioactive materies from the stems and the leaves of spearmint,M.spicata with 95%ethaonl,we studied the biological activities and effects of extracts on P.xylostella of different insect state,the possible mode of action,and analyzed the composition of M.spicata stem and leaf extracts by gas chromatography-mass spectrometry(GC-MS),We also screened several main composition of strong repellent effects on the P.xylostella.Main results of the research are as follows:1 The biological activities of the stem and leaf of M.spicataThe effects of the extract of M.spicata stem and leaf on the feeding,growth inhibition,stomach toxicity and contact toxici of larva,oviposition preference of adult,egg contact and pupal emergence in P.xylostella were investigated.The results showed that the effect of M.spicata leaf extracts was stronger than stem in insecticidal activities.The M.spicata stem and leaf of ethanol extracts in the 3rd instar larvae bioassay showed that the highest antifeedant rate with concentration of 100 mg/mL at 12 h was 100%.the concentration of 24 h antifeedant(AFC50)were 17.61 and 10.19 mg/mL respectively.the growth inhibition rate of feeding at 10th d to larva of P.xylostella was the highest at 74.97 and 76.04%and the growth inhibition concentration(AGCso)was the lowest at 38.71 and 26.90 mg/mL respectively.The median lethal concentration(LCso)at 5 d in stomach were 22.78 and 16.05 mg/mL respectively.The minimum concentration of LC50 was 16.00 and 17.04 mg/mL at 72 h.The M.spicata stem and leaf of ethanol extracts on 100 mg/mL for the oviposition deterrent of adult at 24 h was the maximum rate up to 100%,the oviposition deterrent concentration(AOC50)in 48 h minimum were 12.84 and 10.39 mg/mL respectively.the maximum corrected mortality rates were 81.67 and 83.67%respectively.and the maximum rate of emergence were 52.22 and 41.11%respectively.2 The mechanism of M.spicata stems and leaves ethanol extracts on the 3rd instar larvae of P.xylostellaWhen the 3rd instar larvae were treated with stems and leaves extract respectively,the activity of acetylcholinesterase(AchE)in the larvae showed a trend of initied activation and then inhibition.When the stem and leaf extract was 12.5 mg/mL,AchE activity of the larvae at 12 h were 24.93±0.69 and 22.96±0.16 U/mg respectively;the enzyme activity were 29.89±0.37 and 30.80±0.77 U/mg respectively at 36 h.and the enzyme activity for 48 h were 24.93±0.50 and 24.53±0.90 U/mg respectively.The activity of carboxylesterase(CarE),glutathione S-transferase(GST-s),peroxidase(POD),superoxide dismutase(SOD)and catalase(CAT)of P.xylostella also showed the same trend,first activation and then inhibition after the larvae were treated with the stems and leaves extract treatmented.Finally,the enzyme activity of the treatment group was significantly higher than the control group,and the enzyme activity decreased with the increase of concentration.3 The effective constituents of the ethanol extracts of M.spicata stem and leaf by GC-MSThe analysis of the constituents of the M.spicata stem and leaf extracts by GC-MS,showed that the component of the stem and leaf extracts were obviously different,and the leaf extracts were more complicated than the stem.The highest component of the stems extracts was squalene,and the leaves extract was(R)-(-)-carvone,three highest species of both of their were(R)-(-)-carvone,2,2'-Methylenebis(6-tert-butil-p-cresol)and palmitic acid.4 A preliminary screening of the compounds affected to P.xylostellaWe used(R)-(-)-carvone,2,2'-Methylenebis(6-tert-butil-p-cresol)and palmitic acid,which were richest compounds both in stem and leaf,and moslene to conduct repellent activity investigation.The results showed that the higher concentration of the compounds were more aversion effect than the lowers obviously,the best was(R)-(-)-carvone,and the lowest matching rate of male and female were 7.87 and 11.57%respectively at the concentration of 100 ?L/mL.The lowest matching rate of the male and female were 7.04 and 15.87%at the moslene concentration of 100 ?L/mL.The lowest matching rate of the male and female were 8.10 and 14.54%respectively at the concentration of 2,2'-Methylenebis(6-tert-butil-p-cresol)was 10 mg/mL.The lowest matching rate of the male and female were 26.85 and 20.74%respectively at the concentration of palmitic acid was 10 mg/mL.However when the concentration of 2,2'-Methylenebis(6-tert-butil-p-cresol)and palmitic acid were 1.25 mg/mL,it showed attraction to the males. |
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