Study On Characteristics Of Carboxylesterase And The Effects Of Pesticides On Several Enzymatic Activities In The Malacosoma Neustria Testacea

Tent caterpillars(Malacosoma neustria testacea) is a kind of omnivorous pest all over the world and widely distributed in northeast China, north China, shan xi and other places,it can make the plant leaves incomplete and lead to serious losses to the forestry production. In this paper, we selected Malacosoma neustria testacea as the research object to establish the optimal reaction condition of carboxylesterase by orthogonal experiment method, the experiment would investigate the time-effect and dose-effect relationship with sublethal concentration of carbaryl and omethoate on several enzymatic activities in the Malacosoma neustria testacea. The main results and conclusions are as follows:This experiment messured the effect of the concentrations of enzyme and substrate, pH and temperature of the reaction system, and reaction time on the carboxylesterase of Malacosoma neustria testacea,through analyzing the data from orthogonal experiment with range analysis, variance analysis and multiple comparisons, the optimum conditions for carboxylesterase had been ultimately determined as enzyme concentration0.6beetle/mL, substrate concentration5×10-4mol/L, pH7.0, reaction temperature35℃and reaction time20min.Leaf-dip method was adopted to evaluate carbaryl and omethoate against the third instar of Malacosoma neustria testacea. The results indicated that by24h treatment the median lethal concentration (LC50) with carbaryl and omethoate were93.052and84.555mg/L respectively, and by24h treatment the LC10and the LC20of carbaryl were11.309and23.314mg/L, the LC10and LC20of omethoate were21.094and33.975mg/L respectively.We studied the effect of sublethal concentration(LC10and LC20) of carbary and omethoate on protective enzymes(SCD、POD、CAT) in the Malacosoma neustria testacea,the results showed that,within48h treatment, the activities of SOD were increased by LC20of carbary and omethoate, after12h treatment,the activity was increased by1.67,1.33times comparing to CK, which was at highest level. The activities of POD and CAT in lavae changed dynamicly after treated with sublethal concentration of carbary and omethoate, the POD activities were increased by high concentration of carbary, while omethoate had significant restrain effect on POD activities.The activities of CAT were inhibited at12h and increased at24-48h after treated with carbary, while were induced by omethoate.The result of the effect of sublethal concentration (LC10and LC20) of carbary and omethoate on detoxify enzymes (CarE、GSTs、AChE) in Malacosoma neustria testacea indicated that by the treatment of the LC10concentration of carbary and omethoate, the activities of CarE were inhibited firstly, then increased and inhibited finally. The activities of CarE were decreased within6-48h treatment of the LC20concentration of the two pesticides, comparing to CK, the activities of CarE were decreased by57.3%and58.2%respectively after48h treatment. The activities of GSTs were increased by1.96,1.92times comparing to CK respectively after12h treatment with the LC10concentration of carbary and omethoate, which had a stronger induction than the treatment of LC20. The activities of AChE in lavae were inhibited at different level within6-48h treatment of sublethal concentration of omethoate and carbary, and the concentration of LC20had a stronger inhibition than the concentration of LC10, comparing to CK, the activities of CarE were decreased by50.2and34.3%respectively after48h treatment with the LC20concentration of carbary and omethoate, which were decreased to the lowest level.