| Oedalus decorus asiaticus is one of the important pests in the grassland of China,and a dominant species in the grassland of Inner Mongolia.It is widely distributed and endangers the grassland ecosystem seriously.Chemical control is currently the main measure for controlling O.decorus asiaticus,but it has a significant impact on grassland ecosystems.In this paper,the biological activity and mechanism of three botanical compounds（petroleum ether extract of Stellera chamaejasme root,azadirachtin,thymol and cypermethrin）to O.decorus asiaticus were tested,and the olfactory behavior of O.decorus asiaticus to two plants（S.chamaejasme and Thymus mongolicus）,were studied.The main results are as follows:1.The toxicity of three botanical compounds to O.decorus asiaticus was as follows:non-selective antifeeding effect>selective antifeeding effect>gastric toxicity>comprehensive toxicity>contact killing effect.The non-selective middle antifeeding concentration(AFC50)of the petroleum ether extract of S.chamaejasme root,thymol and azadirachtin against the 3rd instar of the O.decorus asiaticus was 433.97 mg/L,183.35 mg/L and 86.47 mg/L,and the selective middle antifeeding concentration(AFC50)was 460 mg/L,213.38 mg/L and 106.35 mg/L,respectively.The median lethal concentration(LC50)of gastric toxicity was 7976.33 mg/L,269.65 mg/L and 341.07 mg/L,respectively.The contact toxicity was small relatively.2.ATPase,ACh E and total esterase activities of the 3rd instar O.decorus asiaticus could be inhibited by three plant compounds,and the inhibitory effect was positively ralated to the compound concentration,but the inhibition rate was not more than 50%.The GSTs activity and cytochrome P450 increased,while the Car E activity was inhibited after treatment with three botanical compounds at 48 h.3.The olfactory behavior of O.decorus asiaticus to two plants（S.chamaejasme and T.mongolicus）,and three plant compounds（petroleum ether extract from S.chamaejasme,thyme and azadiracthrin）were measured in this paper.The results showed that the repellent rates of thyme against adult of O.decorus asiaticus was 86.67%,and the repellent rates of the aerial part,root and whole plant of S.chamaejasme were 83.33%,81.67%and 80.00%respectively.The repellent rates of the three compounds to the adults of O.decorus asiaticus increased with the increasing of the compound concentrations.The repellent rates of the petroleum ether extract of the root of S.chamaejasme,thymol and azadirachtin to the adults of O.decorus asiaticus were 86.67%,85.00%and 86.67%,respectively at the maximum concentration.4.The EAG response values of the adult of O.decorus asiaticus to the three compounds increased with the increasing of compound concentrations.The EAG values of the adult of O.decorus asiaticus were 0.33 mv,0.67 mv and 0.33 mv when the maximum concentration of neochamaejasmine A,thymol and azadirachtin was 0.3 mg·m L-1,.5.A total of 624 volatile compounds were identified from the aboveground parts of S.chamaejasme,including terpenoids,esters,heterocycles,alcohols,ketones,phenols,hydrocarbons,aldehydes,nitrogen-containing compounds,sulfur containing compounds,amines,acids,etc through GC-MS.The content of terpenoids was the highest among them,with 130 species accounting for 20.8%of the volatile compounds.A total of 884 types of volatile compounds were identified for T.mongolicus,including terpenoids,esters,heterocycles,alcohols,ketones,phenols,hydrocarbons,aldehydes,nitrogen-containing compounds,sulfur-containing compounds,amines,acids,etc.207 types of terpenoids were identified among them,accounting for 23.2%of the volatile components.In conclution,the three plant compounds have insecticidal activity to O.decorus asiaticus.At the same time,the three botanical compounds and two plants have obvious repellent effect on the O.decorus asiaticus.Therefore,the three plant compounds and two piants have a good development prospect in the future. |
