Studies On The Structure And Dynamics Of Arthropod Community In The Two Different Habitats Of Longan Orchards

The investigation of arthropod community in two different habitats of longan orchards was conducted from October, 2005 to October, 2006 in Fuzhou, Fujian province. The structure and dynamics of arthropod community, and the dominant species of pests and natural enemies were studied by analyzing the collected data. The seasonal fluctuation of Conopomorpha sinensis and the community structure and dynamics of the parasitic enemies were also studied. The major results were concluded as follows.The investigation indicated that 15 orders, 103 families and 265 species were recorded from the two different Habitats of longan orchards, including 13 orders, 87 families and 198 species of insects, 14 families and 65 species of spiders, and 2 families and 2 species of mites. 392252 individuals were recorded from the eco-orchard, including 391395 insect individuals belonging to 13 orders, 83 families and 168 species, and 857 spider individuals belonging to 2 orders, 16 families and 60 species. In chemical control orchard, 23070 individuals were recorded, including 22750 insect individuals belonging to 12 orders, 61 families and 17 species, and 320 spider individuals belonging to 2 orders, 12 families and 28 species. Compared with chemical control orchard, the species and the individuals of arthropod community were obviously high in eco-orchard.Dominant rank of species was. analyzed by the dominance index of Berger-Parker. Cornegepsylla sinica and Thysanofiorinia leei were dominant species, and Longan leaf gall midge ,Atropidae sp. and Olethreutes leucaspis were abundant species in eco-orchard. In chemical control orchard, the dominant species were Cornegepsylla sinica and Bemisia tabaci, abundant species were Conopomorpha litchiella and Conopomorpha sinensis.The community structure and dynamics were studied. The investigation indicated that the species and the individuals of arthropod community in the eco-orchard were higher than those of chemical control orchard. Under the effect of seasonal fluctuation of Cornegepsylla sinica which was controlled by different habitats and chemical pesticide, the indexes of diversity and evenness for both arthropod community and pest sub-community in eco-orchard were lower than those of chemical control orchard. For both predatory enemy sub-communities and parasitic enemy sub-communities,the same results could also be obtained. However, they were opposite for neutral insect sub-communities.The similarity of arthropod community, pest sub-community, predatory enemy sub-communities and Parasitic enemy sub-communities was 0．5～0．6 between the eco-orchard and the chemical control orchard. For parasitic enemy sub-communities and neutral insect sub-communities, it was 0．8462 and 0．8125, respectively.From October 2005 to October 2006, the temporal dynamics of richness of arthropod community and various sub-communities appeared the same trend: Up～down～up～down. In general, the species richness of eco-orchard was higher than those of chemical control orchard. In the eco-orchard and the chemical control orchard, there was a prominent difference in individual abundance of arthropod community and pest sub-community. Individual abundance of arthropod community in the eco-orchard was higher than those of chemical control orchard, climbed sharply and reached the highest point of 165583 in April. The diversity index of arthropod community and various sub-communities was quite similar. The evenness index appeared the same tendency with the diversity index. However, the tendency was opposite for the dominant concentration index.From August 20 to September 20, insect investigation indicated that 6 orders, 17 families and 21 species were recorded from the fruit, including 6 orders, 16 families and 20 species from the eco-orchard and 5 orders, 10 families and 12 species from the chemical control orchard. During the period of September 9, species and individuals of insect are significantly decreased mainly due to the application of chemical pesticide.The individuals of Conopomorpha sinensis was gradually increased wih temporal dynamics changes at both the Eco-orchard and the chemical control orchard, and the richness of the chemical control orchard is higher than those of the Eco-orchard. The application of chemical pesticide appeared no obvious control effects on the seasonal fluctuation of Conopomorpha sinensis. The rate of damaged fruit in the chemical control orchard was higher than those in the Eco-orchard, 33．11% and 6．95%, respectively. It indicated that the harm of Conopomorpha sinensis was extremely serious. The investigation of Conopomorpha sinensis in leaves indicated that the pupa quantity kept on increasing, and up to its zenith of 70 pupae in September. Pupae were still found in December.According to the investigated data of population in laboratory and field, Apanteles grandiculus played a significant role in the control of Conopomorpha sinensis. followed by Camtylomma chinensis and Chrysopa sinica. The parasitic natural enemies started to appear in May, the population and the number of parasitic natural enemies kept on increasing, and reached the peak in September. Apanteles grandiculus was the dominant specie of parasitic enemy to control Conopomorpha sinensis. During the period of September and October. Phanerotoma minuta and Elasmus sp. provide a significant control effect against Conopomorpha sinensis Population.