Study On Insect Community Structures In Aquatic Vegetable Areas And Effects Of Different Aquatic Vegetables On Development And Insecticides Susceptibility Of Spodoptera Litura

Aquatic vegetables cover all crop species growing in paddy fields, pools and lowlands and it is a special planting in china, Spodoptera litura Fabricius (Lepidoptera: Noctuidae) was a kind of worldwide pest and broke out intermittently on aquatic vegatables. In the exerperants, The diversity of insect community structures in different aquatic vegetables, the influence of feeding on different aquatic vegetables to growth, reproduction, susceptibility, activity of detoxifcation enzymes of Spodoptera litura were studied with the different aquatic vegetables were be took as host plants.1 Study on insect community structures and dynamics analysis in different aquatic vegetable areas in Wuhan.The diversity of insect community structures in different types of aquatic vegetables in Wuhan in Hubei province were investigated with visual and net method from May to October in 2008. The results indicated that there were 9169 individuals belonging to 11orders,48 families,104 species. Among them, Rhopalosiphum nymphacae(Linnaeus), Prodenia litura (Fabricius), Saccharosyne Procerus (Matsumura), Scirpophage praelata (Scopoli) and Galerucella Birmanica (Jacohy) were the main injurious insects while Odonata and Coccinellidae were the primary natural enmies. The analyses on the community structures indicated that the diversity index of insect community are remarkable difference in different vegetations, and among them diversity of insect community in Water dropwort is the highest, while Lotus is the lowest. Insect community structures of Water dropwort is the most stable, Water chestnut takes the second place, while the diversity index of insect communities in Lotus is high in the metaphase, but low in prophase and anaphase, and the diversity index of insect communities in water bamboo is low in the metaphase, but high in prophase and anaphase.2 Effects of different aquatic vegetables on the development and nutrition utilization of Spodoptera litura.To understand damage of Spodoptera litura to aquatic vegetable and provide basic information for integrated management of the pest, we investigated effects of feeding Nelumbo nucifera, Oenanthe stolonifera, Colocasia esculenta, Eleocharis tuberose, Brassica rapa pekinensis and Artificial diet on the growth and development of S.litura, and evaluated the taxis and the nutrition utilization to different aquatic vegetables of S.litura using a life table method. The results indicated that the taxis of the larva to the aquatic vegetables was N. nucifera, O. stolonifera>B. pekinensis> C. esculenta>E. tuberose, and the taxis of the adult to aquatic vegetables was N. nucifera> C. esculenta> B. pekinensis>O. stolonifera>E. tuberose. S.litura could complete their life cycle on all four aquatic vegetables. The survival rate of larvae and the ratio of larvae developed to moth emergence when larvae fed on N. nucifera, C. esculenta and Artificial diet were significantly higher than that on E. tuberose, while larval duration were significantly shorter than that on E. tuberose when larvae fed on N. nucifera and C. esculenta. The pupal weight and mean fecundity when larvae fed on N. nucifera and Artificial diet were higher than that on other vegetables, the mean generation time(7) and the doubling time(D7) when larvae fed on E. tuberose were significantly higher than that on other five treatments, while the intrinsic rate of increase(rm) and the finite increase rate were significantly lower than that on other five treatments, The net reproductive rate(Ro) when fed on N. nucifera and C. esculenta were similar and significantly higher than that fed on O. stolonifera and E. tuberose but lower than feeding on Artificial diet. The nutrition indexes of 5th instar larvae on consumption of the six treatments indicated that the relative growth rate(RGR)in larvae feeding on E. tuberose was significantly lower than that on other five hosts, and the approximate digestibility(AD)was high but the efficiency of conversion of digested food(ECD) was low. It was concluded that N. nucifera was the most suitable for S. litura, and it has potential outbreak on the O. stolonifera.3 Effects of different aquatic vegetables on the insecticides susceptibility of Spodoptera litura.In order to understand influence of aquatic vegetable to Spodoptera litura and provide basic information for integrated management of the pest, we investigated effects of feeding different aquatic vegetables on the susceptibility to five differdent pesticides and the activity of CarE, AChE and GSTs of S.litura, and the results indicated that the susceptibility of S.litura to chlorfluazuron, Chlorpyrifos, indoxacarb, Chlorfenapyr and Emamectin-benzoate was different when feeding on different aquatic vegetables. Activity of detoxifcation enzymes of S.litura were different when feeding on different aquatic vegetables, and the activity of CarE sequence was N. nucifera> artificial diet> O. stolonifera>C. esculenta, the order of activity of AChE was C. esculenta>artificial diet> N. nucifera>O. stolonifera, the activity of GSTs was artificial diet>O. stolonifera>N. nucifera>C. esculenta, the activity of MFO was O. stolonifera>C. esculenta>N. nucifera> artificial diet. It demonstrated that the higher detoxifcation of enzymes were related to the different susceptibility to insecticides when feeding on different aquatic vegetables. Spodoptera litura is highiy susceptibile to Hexaflumuron and chlorfluazuron among 16 insecticides.