| In order to reduce the use of insecticides, increase control effect of insecticides, the synergism of enzyme inhibitors, 1227, C8-10 and silicone breakthru S240 to insecticides on the S.exigua were studied. meanwhile, we investigate the surface tentions, the expanded diameter and the maximum retention on cabbage leaves of 1227, C8-10 and silicone breakthru S240 solution of different concentration, and synergistic mechanism of cationic 1227 against S.exigua were studied. In order to reduce the destruction of insecticides to natural enemies of S.exigua, we investigate the effect of 9 insecticides on the development of H. axyridis, C. sinica, S. manilae and T. remus. The results were as follow.1. The experiment of interaction of enzyme inhibitors with insecticides indicated that four different enzyme inhibitors showed obvious restraint to chlorfenapyr and indoxacarb (Synergism ratio between 0.25 and 0.96). And four different enzyme inhibitors showed synergism to methomyl, emamectin benzoate and tebufenozide on S. exigua, Synergism ratio between 1.22 and 4.2.2. In order to provide theoretical proofs for the application of two cationic adjuvants and silicone Breakthru S240, the synergism of three adjuvants to beta-cypermethrin, chlorpyrifos and chlorfenapyr on 3rd-instar larvae of the Spodoptera exigua (Hübner) were studied by dipping method. Herein we investigate the surface tentions, the expanded diameter and the maximum retention on cabbage leaves of 1227, C8-10 and silicone breakthru S240 solution of different concentration. Synergism experiment showed the synergism ratios of C8-10 and 1227 on beta-cypermethrin, chlorpyrifos and chlorfenapyr were enhanced as the adjuvants concentration increased on Spodoptera exigua(Hübner). The synergism ratio of C8-10 and 1227 between 1.2 and 2.5 at the concentration of 300 mg·L-1, 900 mg·L-1, and the synergism ratio of silicone breakthrough S240 to beta-cypermethrin, chlorpyrifos and chlorfenapyr varied from 1.5 to 2.0 at the concentration of 900 mg·L-1. The surface tensions of silicone breakthrough S240 and C8-10 water solution were 20 mN/m at the concentration of 900 mg·L-1, which were 3.79 and 3.31 fold to water solution. Silicone breakthrough S240 could significantly increase the solution expansion diameter to 180mm, which was 2.76-fold to water solution at the concentration of 900 mg·L-1. The maximun retention of silicone breakthrough S240, C8-10 and 1227 solution were 5.6, 5.4 and 5.0μg/cm2 at the concentration of 900 mg·L-1. 3. Studies were carried out to investigate the synergism and synergistic mechanism of cationic 1227 against S.exigua in this paper. The results demonstrated that cationic 1227 increased the toxicity of chlorpyrifos to the S.exigua, with synergistic ratios of 1.54 and 1.59 at the concentration of 270 mg·L-1 and 810 mg·L-1. The penetrating rate of chlorpyrifos treated with cationic 1227 were recorded at 52.84% and 50.24% for 90 mg·L-1 and 810 mg·L-1 after 6 hours, and in contrast to this, control and 10 mg·L-1 treatment had a penetrating rate of 38.06% and 36.49%. And observation in a scanning electron microscope showed that the larvae S.exigua cuticular super micro structure of administration group with 10, 90 and 810 mg·L-1 cationic 1227 were in loose arrangement, large gap and that of the control group was in close arrangement, small gap, but the difference was insignificant between the administration group. Biochemical assays showed that there were no effects of the cationic 1227 on the carboxyl esterase, acetylcholinesterase and glutathione S-transferase.4. we investigate the effect of 9 insecticides on the development of H. axyridis, C. sinica, S. manilae and T. remus. S. manilae and T. remus were sensitive to all 9 insecticides (LC10 less than 0.65 mg·L-1), while H. axyridis and C. sinica were less sensitive (LC10 between 1 x 10-5 mg·L-1 and 22.52 mg·L-1). The degradation dynamics showed that all insecticides had longer residual toxicity to parasitoid adults than predator adults. There were no direct effects on pupae associated with the H. axyridis, C. sinica, S. manilae and T. remus. S. manilae and T. remus, while chlorpyrifos, methomyl, and tebufenozide were moderately toxic to H. axyridis pupae (LC10: 128.94, 52.77, 39.6 mg·L-1). Larvae of H. axyridis were sensitive to all 9 insecticides (LC10 between 3.5 x 10-3 mg·L-1 and 2.86 mg·L-1), but none toxic to C. sinica larvae and T. remus larvae. However, the effect on S. manilae larvae depended on toxicity to S. exigua. These results demonstrate that insecticides should be selected according to the target species and the developmental stage of any natural enemies. Moreover, releasing natural enemies based on the safest timing would reduce the risk that insecticides pose to natural enemies. |
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