The Selective Toxicity And The Selection Mechanism Of The Chlorfenapyr To Bombyx Mori L. And Spodoptera Exigua(Hübner)

The Bombyx mori L. and Spodoptera exigua H. were studied as the test insects in the study. The selective toxicity of the test insects were determined, the mitochondria were extracted and compared the block difference of chlorfenapyr to the oxidative phosphorylation of the two insects, compared the difference of the P450 and discussed the cooperative relation of the detoxifying enzymes and the penetrating action to the the selective toxicity of the chlorfenapyr between the two insects .The mainly results are as follows :1. The toxicity of chlorfenapyr to Bombyx mori L. is tested by the food intake method from the second instar of the Bombyx mori L..The results showed that The 48 h LC50 to the four instars of the Bombyx mori L. were 122.06, 85.25, 103.78and 243.14 mg·L-1,respectively, the third instar larvae of the Bombyx mori L. were the most sensitive to the pesticide .The toxicity of chlorfenapyr to Spodoptera exigua H. is tseted by the leaf dipping method from the second instar of the Bombyx mori L..The results showed that the 48-h LC50 to the four instars of the Spodoptera exigua H.were 0.1979, 0.2774, 0.4307and 0.9643 mg·L-1,respectively.The second instar larvae of the Spodoptera exigua H. were the most sensitive to the pesticide.The toxicity ratio to the second instars between the Bombyx mori L. and Spodoptera exiguai H. was 616.77, and to the third instars, the ratio between them was 307.32.2. We determined synergists PBO,SV1,DEM and TPP increasing the toxicity effect of chlorfenapyr by drop method. The synergism effects were significant with chlorfenapyr dropped two kinds of insects after TPP treated, the synergism ratio of chlorfenapyr to Bombyx mori L. was 2.83 fold while that of Spodoptera exiguai H.was 2.9 fold. With DEM treated, the synergism effects to Spodoptera exiguai H. was obvious with synergism ratio of 3.61-fold,and to Bombyx mori L. was weak with synergism ratio of 1.06-fold. With SV1 treated, there was weak synergism to Bombyx mori L. while not significant synergism to Spodoptera exiguai. With PBO treated, there was not obvious synergism to both insects, whereas decreased toxicity to diamondback moth was discovered.3. The uncoupling of oxidative phosphorylation experiments indicated that there was significant differentce of inorganic phosphorus concent change(ΔPi) during oxidative phosphorylation between Spodoptera exiguai H. treatment group and control group.ΔPi showed an increase tendency with the concentration increase. In contrast, there was no difference in the same experiment of Bombyx mori L..Great variation ofΔPi indicated that oxidative phosphorylation was influenced significantly.After treated Bombyx mori L. with chlorfenapyr,ΔPi did not change obviously during mitochondrial uncoupling process, this showed the toxicity of chlorfenapyr to Bombyx mori L. was low.4. It's an effective way to rise the respiration rate rapidly to against toxicant infecting for insects. The results of the experiments indicated that the climacterics are seen in all the treatments of Spodoptera exiguai H. while only observed in the Bombyx mori L. treated with chlorfenapyr at the dose of 50μg/g, but the respiration tendency of the treatments are similar as the control. The respiration peak of beet Bombyx mori L. were observed at 9h, 6h after treated with chlorfenapyr at the dose of 25μg/g, 50μg/g and were 1.5, 3.6 times higher than control, respectively.5. For the addition of synergists,there were different effects. Synergists had different degrees of inhibition effects on carboxylesterase,GST of Bombyx mori L.,but it was no effects on MFO.Chlorfenapyr had different degrees of activation effects on detoxifying enzymes of Bombyx mori L. and Spodoptera exiguai H.. In a certain range, synergist dose and enzyme inhibition rate presented positive correlation,when the dose exceeded a certain range, enzyme inhibition rate was kept at a certain level, it was no longer increased with the dose (for example,PBO effected on MFO and DEM effected GST ). Because of small amount and low activation of MFO in Bombyx mori L.,so it can't determine its activation and contents.6. The phenoloxidase of the Bombyx mori L. and Spodoptera exigua H. can be activated by the chlorfenapyr.The enzymatic specific activity and its growth rate of the Bombyx mori L. increased gradually with the increasing of the time; And its enzymatic specific activity of the Spodoptera exigua H. also increased with the increasing of the time within the limited range of the concentration,while the increasing rate was increased at first and then decreased.