| The toxicities of tebufenozide derivatives 0593 and 0673 in lab against Spodoptera exigua (Hübner),Prodenia litura (Fabricius),Plutella xylostella (Linnaeus),Helicoverpa armigera (Hübner) and Ostrinia furnacalis (Guenee) were investigated with leaf-dip, dipping and topical application, the tebufenozide was used as control. The action modes of 0593 and 0673 were evaluated. The effects of 0593 on development of S. exigua were studied with leaf-dip. The mechanisms of 0593 and 0673 were studied in order to provide direct academic foundation to their exploitation. The results could be summarized as follows:1. The toxicities of 0593 and 0673 against five Lepidoptera pests were higher evidently than those of tebufenozide. Compared with that of tebufenozide, the contact toxicities of 0593 and 0673 against 4th-instar larvae of S. exigua were 11.3 and 7.4 folds;the contact toxicities of 0593 and 0673 against 4th-instar larvae of P. litura were 30.4 and 24.7 folds;The toxicities of 0593 and 0673 against 3rd-instar larvae of P. xylostella with dipping method were 4.7 and 4.5 folds and the contact toxicities of 0593 and 0673 against 3rd-instar larvae of H. armigera were 15.5 and 15.2 folds;the contact toxicities of 0593 and 0673 against 4th-instar larvae of O. furnacalis were 1.3 and 2.0 folds, respectively. The differences of toxicities between 0593 and 0673 were significant.2. The contact toxicities of 0593 and 0673 were higher than those of tebufenozide. The LD50 of contact toxicities 0593 and 0673 against 4th-instar larvae of S. exigua were 5.477μg/g and 8.370μg/g, the LD50 of tebufenozide was 61.663μg/g.The contact toxicities of 0593 and 0673 against 4th-instar larvae of S. exigua were 11.3 and 7.4 folds respectively compared to that of tebufenozide. The stomach toxicities of 0593 and 0673 were higher than that of tebufenozide against 2nd-instar larvae of S. exigua. The LC50 of stomach toxicities 0593 and 0673 against 2nd-instar larvae of S. exigua were 6.515μg/g and 8.944μg/g, the LC50 of tebufenozide was 14.418μg/g.The stomach toxicities of 0593 and 0673 against 2nd-instar larvae of S. exigua were 2.0 and 1.6 folds compared to that of tebufenozide, respectively.The LD50 of contact toxicities 0593 and 0673 against 4th-instar larvae of P. litura were 47.981μg/g and 58.962μg/g, the LD50 of tebufenozide was 1457.6μg/g.The contact toxicities of 0593 and 0673 against 4th-instar larvae of P. litura were 30.4 and 24.7 folds compared to that of tebufenozide, respectively. The stomach toxicities of 0593 and 0673 were higher than that of tebufenozide against 3rd-instar larvae of P. litura. The LC50 of stomach toxicities 0593 and 0673 against 3rd-instar larvae of P. litura were 18.423μg/g and 17.098μg/g, the LC50 of tebufenozide was 53.534μg/g.The stomach toxicities of 0593 and 0673 against 3rd-instar larvae of P. litura were 2.9 and 3.1 folds compared to that of tebufenozide, respectively.3. Treated with tebufenozide and 0593, the 2nd-instar larvae of S. exigua died unceasingly after 72h; the pupation rate and adult emergence ratio were decreased, the number of abnormal pupae was increased; in addition, eggs laid per female and egg hatchability were also reduced significantly, and the fecundity was affected significantly,too. Tebufenozide derivative 0593 showed more disadvantageous influence than tebufenozide on the fecundity of S. exigua at the same concentration. The results suggested that tebufenozide derivative 0593 is a pesticide with higher bioactivity against lepidopteran larvae and stronger harmful effects on their development and fecundity than tebufenozide, so it's worth exploiting. Treated with 0593 (at the dose of 0.2μg/mL,0.5μg/mL)and tebufenozide (at the dose of 0.5μg/mL), the cumulative mortality before pupating were 44.0%, 86.0% and 55.0%, which were higher significantly than control (20.0%).At the same time, the pupation rates were 70%, 17.5% and 56.25% compared with control. Abnormal pupatio ratio of 0593 was 28.6% at the dose of 0.5μg/mL.The adult emergence ratio was 86.0%, which was higher than that of 0593 0.2μg/mL,0.5μg/mL and tebufenozide 0.5μg/mL (66.7%, 46.4% and 61.1%).Eggs laid per female treated withe 0593 at the dose of 0.5μg/mL, was the lowest, 75% of control, the others were 64% and 66% of control. Egg hatchability of S.exigua treated with 0593 at the dose of 0.2μg/mL,0.5μg/m L and tebufenozide at the dose of 0.5μg/mL were 72.0%, 59.1% and 70.6%, respectively, which were lower than control significantly. The fecundity was also affected by pesticides significantly. Tebufenozide derivative 0593 showed more disadvantageous influence than tebufenozide on the fecundity of S. exigua at the same concentration.4. New tebufenozide derivatives 0593 and 0673 could affect seriously enzyme system differently. First, pesticide the expression of chitinase was induced 24h after treated with 0593, 0673 and tebufenozide, the activities were 3.1294, 2.8347 and 2.5120 OD/mg pr., which were 2.08, 1.89 and 1.67 folds compared with control. The activities were decreased gradually 24h after treatment; the values were 2.3073, 2.0451 and 1.7501 OD/mg pr. respectively. And then, the activities were declined unceasingly, the values were 1.6775, 1.0965 and 1.1174 OD/mg pr. at 72h.The activities treated with pesticides were higher than control which were 1.3012 and 0.6687 OD/mg pr.. Second, the activity of phenoloxidase was inhibited. There was no significant difference among all treatments 24h after treatment. Then the activity began to decrease. The enzyme activities of 0593-treatment and 0673-treatment at 48h were 0.1079 and 0.1297△OD/min·mg pr., respectively, and were lower than those of tebufenozide and control obviously. Then the activities of them rise slowly. However, they were still lower than thoe of tebufenozide and control. Third, the activity of cellulase was inhibited. There was no significant difference among all treatments 24h after treatment. Then the activity began to increase, the highest activity occurs at 48h. The activities of 0593, 0673 and tebufenozide increased in turn and were 44%, 67% and 89% of control. The activities of 0593 and 0673 were decreased and those of tebufenozide and control were increased unceasingly. Last, the activity of O-demethylase was induced. The activities of 0593 and 0673 were 0.2191 and 0.2359 nmol/min·mg pr. and were 2.38 and 2.57 folds compared with control. Compared with tebufenozide, the activities of 0593 and 0673 were inhibited.5. The studies on the effect of 0593, 0673 on cuticle indicated that 0593 and 0673 could cause insect larvae a prematureand incomplete lethal molt and the symptom of surplus ecdysone. The old and new cuticle separated and filled with translucent liquor between them. The body of insect shrunk, intenerated and then died at last. |
