The Research On Arthropoda Community In Cottom Field And Bio-Control Of Cotton Red Spider Mite

In order to provide a scientific basis for the pest control and protection & utilization of their natural enemies, the system investigation on organizational feature, population dynamic and spatio-temporal niche of arthropod community was carried out in the cotton fields of Changsha, Hunan province, from 2013 to 2014. The investigation was started in June and ended in September which mainly studied the contends about population dynamics, regulation of arthropod community in different planting density in the past two years, difference of arthropod community in different density, spatio-temporal niche and niche overlap and so on, which layed a foundation for further studying of arthropod community and proceeding of biological control by utilizing the natural enemies. The main results showed as below:The studied arthropod covered 37 species in 2014, which belongs to 21 families and 11 orders. The dominant species of pests are Aphis gossypii (Glover), Tetranychus cinnabarinus (Boisduval), Thrips flavus (Schrank), Empoasca biguttula (Ishida), Frankliniella intonsa (Trybom) and Bemisia tabaci (Gennadius); The dominant species of natural enemies are T.squamata (Karsch), P. japonica (Thunberg), Tetragnatha extensa (Linnaeus), Chrysoperla nipponensis (Okamoto), Coleosoma octomaculatum (Boes. et Str) and Neoscona theisi (Walckenaer). The arthropod community structure in cotton fields in 2013 is complex, which covered a total of 33 species in 20 families and 11 orders. The main pests in cotton fields are Amrasca biguttula, Empoasca flavescens, Tetranychus cinnabarinus, Aphis gossypii and Bemisia tabaci, and their natural enemies are Coleosoma octomaculatum, Tetragnatha squamata, Propylaea japonica, Scolothrips sexmaculatus and Chrysoperla nipponensis.On the condition of high density cultivation in cotton fields, the quantities and species of arthropod both increase comparing to 2013, the structure of community turns more complex and stable. The quantities of arthropod community are the least in the early period, the diversity and evenness of pest subcommunity are low, but the concentration ratio is high, which keeps increasing until reaching the maximum in the middle and later period of August; the diversity and evenness of pest subcommunity are high in the early period, but the concentration ratio is low, which keeps in a low value stably. The natural enemy subcommunity and pest subcommnunity shows relaying relationship in quantitative terms. Tetranychus cinabarinus and Aphis gossypii should be controlled in the first ten days of June and Empoasca flavescens and Amrasca biguttula in mid-July. Coleosoma octomaculatum and Scolothrips sexmaculatus are dominant enemies in the earlier period and Tetragnatha squamata in the middle and later periods. Tetragnatha squamata, Propylaea japonica and Chrysoperla nipponensis should be protected and utilized because of their wide spatio-temporal niche.To detect the effect of old traps and new trap trap, complement to the composition of arthropod community in cotton fields, improve the cotton plant monitoring system, select the sex pheromone lure core of Spodoptera litura, Heliothis assulta, Pectinophora gossypiella, Helicoverpa armigera and Agrotis ypsilon, to investigate. Effect of new type of trap was better than the old trap, the sex pheromone lure core of Spodoptera litura was best. In late June and early July, August to October is the occurrence of the Spodoptera litura, when should be focus on prevention and control. Pectinophora gossypiella, Helicoverpa armigera, Heliothis assulta and Agrotis ypsilon which appeared before early August, so using chemical control measures to control and prevention at the early stage of the cotton growth.For coordinating the effect of between chemical pesticides and natural enemies on the two-spotted spider mite, the study about its comprehensive control was carried out by selecting five common kinds of pesticides, including abamectin, azadirachtin, sophocarpidine, pyrethrin and imidacloprid, and its natural enemies-Amblyseius cucumeris. The study results show that it can effectively prevent cotton red spider mite by the way of using integrated control combining chemical prevention with biological control, the 1.8% abamectin (1:8000) was sprayed after 6 days to release predatory mite, its relative control efficience was 96.63±0.32% 20 days later. The 0.3% azadirachtin (1:250) was sprayed after 7 days to release predatory mite, the relative control coeficience of it was 59.7±2.01% one day latter,90.16±0.66% 20 days later.0.5% sophocarpidine (1:2000) was sprayed after 6 days to release predatory mite, the relative control coeficience of it was 82.65±1.13% 20 days later.