Biological Activity Of Pogostone Against Spodoptera Litura And Its Effect On Detoxification Enzyme Of Spodoptera Litura(Lepidoptera:Noctuidae)

Pogostone is a compound purified from patchouli essential oil which has insecticidal activity. To ascertain the insecticidal activity of pogostone is the foundation of its application. The biological activity of pogostone and its effect on detoxification enxzyme were systematically studied, focusing on the object of tobacco caterpillars, to provide a theoretical basis for pogostone in-depth development and research. The main results were as follows:1 The contact toxicity of pogostone against the larvae of Spodoptera litura was determined by spot method. The results showed that the corrected mortality rate increased with the increasing of the concentration of pogostone. At the same concentration, the lower the instar larvae of S. litura was, the better effect of contact toxicity was. After treated with 16mg/m L, the corrected mortality rates against 3rd instar, 4th instar and 5th instar larvae were 100%, 100% and 76%, respectively.2 The antifeedant effect of pogostone against the larvae of S. litura was determined by dipping leaf disc. The results showed that the no-choice antifeedant rate increased with the increasing of the concentration of pogostone. After treating with 16mg/m L, the antifeedant rates against 3rd instar, 4th instar and 5th instar larvae were 100%, 100% and 99.66%, respectively. The median antifeedant concentration(AFC50) values were 1.53mg/m L, 2.09mg/m L and 2.17mg/m L, respectively.3 The oral toxicity of pogostone against the larvae of S. litura was determined by leaf feeding method. The result indicated that the corrected mortality rate increased with the increasing of the concentration of pogostone. The corrected mortality rate was also increased with the increasing of the treatment time. Comparing the activity of oral toxicity at the same concentration, 3rd instar larvae was the best, 4th instar was second while 5th instar was the worst. After treating with 16mg/m L for 72 h, the corrected mortality rates against 3rd instar, 4th instar and 5th instar larvae were 86%, 52% and 18%, respectively. The median lethal concentration(LC50) value of 3rd instar larvae was 6.99mg/m L.4 The growth and development inhibition assay of pogostone against the larvae of S. litura was determined by dipping leaf method. The result indicated that larval duration prolonged, larval weight, pupal rate and emergence rate decreased with the increasing of the concentration of pogostone. There was little influence on pupal duration and adult duration. Comparing the activity of growth and development inhibition, 3rd instar larvae was the best, 4th instar was second while 5th instar was the worst. After treating with 16mg/m L for 72 h, the growth inhibition rates against 3rd instar, 4th instar and 5th instar larvae were 98.05%, 93.50% and 70.12%, respectively; and the emergence rates were 6%, 82% and 72% after 24 h, respectively. It showed that pogostone had a certain growth and development inhibition of S. litura.5 The acetylcholinesterase(Ach E) of the larvae of S. litura inhibited at first, then increased, and inhibited finally after treated with different concentration of pogostone and different time. When treated with 2mg/m L, 4mg/m L and 8mg/m L for 0h, the inhibition rates of Ach E were 19.19%, 14.52% and 22.31%, respectively. After 18 h, the rates were 21.52%, 32.94% and 15.84%, respectively.6 The influence on glutathione-S-transferases(GSTs) and carboxylesterase(Car E) in the midgut of the larvae of S. litura was inhibited firstly and then increased. Namely, both of the enzymes had a certain inhibitory action after treated with pogostone, but increased gradually with the extension of treatment time and then became stable. After treated with 4mg/m L for 12 h, the inhibition rates of GSTs and Car E were 7.83% and 37.86%, respectively.These studies proved that pogostone possessed certain stomach activity and strong contact, antifeedant and growth inhibition activities against S. litura. So the pogostone has the potential for development into insecticide. And Car E may play an important role in the site of pogostone against S. litura.