Study On Artemisia Argyi Extracts Against Control Effect And Mechanism Of Ectropis Obliqua

In this experiment, the effects of the extracts with95%ethanol from Artemisiaargyi against3rdinstar larvae of Ectropis obliqua Prout were studied, includingcontact toxicities,stomach toxicities,antifeedant bioactivities and growth inhibitionbioactivities.To determine the change in activities of polyphenol oxidase (PPO) andperoxidase (POD) of tea leaves sprayed with the extracts, We selected two kinds oftea cultivars,Longjing43and Fuyun6,both of which had a significant difference oninsect resistance. After that,we determined the change of activities of PPO and PODin tea leaves,with and without spraying,eaten by3rd instar larvaes of Ectropisobliqua Prout. Finally,we detected the change in activities of PPO,POD andAcetylcholinesterase(AChE) in the bodies of Ectropis obliqua Prout,which had eatenthe sprayed tea leaves,and all the survived3rd instar larvaes of Ectropis obliqua Proutwere researched,containing length,weight,pupation rate and adult emergence rate ofthem.The results were as followed:1. The results from determining the effects of95%ethanol extracts from Artemisiaargyi on3rd instar larvaes of Ectropis obliqua Prout suggested that the extracts hadmany functional patterns against the larvae of Ectropis obliqua as anti-feeding,contacting toxicity, stomach poisoning and inhibiting growth activities. The higherconcentration, the more obviously the effect on the pest was. In the test ofcontacting toxicity and stomach poisoning, the corrected mortality of3rdinstarlarvae of Ectropis obliqua reached66.14%and78.16%treated by contacting andpoisoning at72h, respectively. For the anti-feeding, the results of the antifeedanteffect showed that concentration of100mg/ml had good effect for the larva, theantifeedant effect were56.77%and46.01%after12h and24h, respectively. Theextracts also had significant inhibition to growth and development of larvae theinhibition rate at24h and48h after treatment were54.83%and68.32%atconcentration of100mg/ml, but lower than the control group’s.2. The results from determining the change in activities of PPO and POD indicatedthat: the tea leaves, sprayed with the extracts, had higher activities of PPO and PODthan the control group’s,but Longjing43had a bigger change thanFuyun6.Longjing43had a peak value3d after treatment, earlier and higher thanFuyun6.For the POD, the extracts had more obvious effects on Longjing43thanFuyun6. Longjing43had a peak value2d after treatment, while Fuyun6had a peakvalue5d after treatment lower than the control group’s.In addition, tea leaves which eaten by3rd instar larvaes of Ectropis obliquaProut had higher activities of PPO and POD than the control group. The activityincreasing degree is higher than Fuyun6which showed that PPO and POD played asignificant role in resisting insects of tea trees. insect-resistance tea cultivars shouldhave a bigger change than the susceptible cultivars.There was a certain degree of change in activities of PPO and POD in tea leavesof the two cultivars which were eaten by3rd instar larvae of Ectropis obliqua Proutand sprayed with extracts, and Longjing43had a bigger change than Fuyun6, This shows that susceptible cultivars’insect-resistance could be enhanced by the extractin a larger range than insect-resistant cultivars.3. We measured activities of PPO,POD and AChE in the bodies of3rd instar larvaesof Ectropis obliqua Prout after eating tea leaves which is treated by differentextracts.The result is that the activity of each treatment is different trends, in theend the experimental group’s activities are inhibited by certain.The inhibition ofPPO and POD activity appeared relatively late,but AChE activity was inhibitedbeginning in each treatment, the inhibition rate of AChE activity peaked at24h,after gradually decreased with time.There are significant difference between thedifferent treatments, each time period,the inhibition rate of the Deltamethrin groupis the highest,the mixture of Deltamethrin and extract group was higher than theextract group.4. The survived larvaes after eating the tea leaves treated with the extract had asignificant difference in the length and weight compared with the control group.For mature larvaes survived from the Longjing43which was treated with100mg/mL concentration of the extract, its length and weight were18.71mm and52.03mg respectively, while the length and weight of larvaes in the control groupwere23.18mm and109.05mg. For larvae survived from the Fuyun6, its length andweight was the shortest and lightest. Larvae were heavier and longer than thecontrol group when the extract’s concentration was10mg/ml. There was a negativecorrelation between the length and weight of larvae and the concentration ofextracts, that is to say, the higher the concentration is, the slower length and weightit gets. The conclusion was evidenced by the result concerning the relation betweengrowth inhibition rate and antifeedance rate.5. Tea cultivars treated with different concentrations of the extract in which larvae’pupation rate and adult emergence rate are different. Not larvae’ pupation rate andadult emergence rates were not always lower than the control group, but pupationrate and adult emergence rate didn’t have a distinct regularity in the two teacultivars. Those suggested that there is no obvious relation between the pupationrate and adult emergence rate of larvae and the concentration of the extract.6. From the above, Artemisia argyi extract play better control effect by increasinginsect resistance of tea and impacting biological activity of Ectropis obliqua.