Studies On The Diversity Of Arthropod Community And Major Pests' Ecological Control In Navel Orange Orchard

The diversity of arthropod community and major pests' ecological control in navel orange orchards were studied at Yongtai County, Fujian Province, from October, 2005 to December, 2006. The results were summarized as follows.1 Structure and diversity of the arthropod community in the navel orange orchardA total of 176 727 individuals belonging to 157 species of arthropods were collected and identified from the navel orange orchards, including 68 species of pests, 21 species of neutral insects, 56 species of predators and 12 species of parasitoids. They belonged to 91 Families of 16 Orders of two Classes.Based on the calculation of the dominance index, it showed that: the dominant species in the group of pests were Panonychus citri Megregor, Dialeurodes citri (Ashmead) and Phyllocnistis citrella Stainton; Toxoptera aurantii Boyer de Fonscolombe was frequent specie; Aphis citricola Van der Goot and Myzus persicae Sulzer were the occasional species. In the community, there were 34.05% Panonychus citri and 62.47% Dialeurodes citri, the biggest abundance were given by them. Amblyseius nicholsi Ehara et Lee, Amblyseius cucumeris Oudemans and Erigonidium graminicolum (Sundevall) were the major species in the group of predators; Aphidencyrtus aphidivorus (Mayr), Anastatus sp., Trichogramma sp., Amitus hesperidum Silv. were the major species in the group of parasitoids; Bradysia odoriphaga Yang et Zhang, Tipula sp. and Apis cerana Fabricius were the major species in the group of neutral insects.The diversity and evenness of arthropod community in navel orange orchards were low, and the dominant concentration was high, the distribution of individuals was not even, pest's outbreak was more possible. The fluctuations of arthropod community and dominant species of different groups were analyzed. The results showed that natural enemies had an obvious controlling effect on navel orange pests. In winter and spring, predators played the major effect of controlling pests, in summer and autumn, predators and parasitoids controlled the pests together.Two orchards under different management were compared, the species and individuals of the natural orchard Hefeng orchard were all above Guoling orchard that control pest by pesticide; the arthropod community diversity and evenness of Hefeng orchard was higher than Guoling orchard, but the dominant concentration was lower, this suggested that the pest outbreak was more possible in Guoling orchard than in Hefeng orchard.2 The ecological control of the major pests in navel orange orchardThe results of studying on citrus whitefly showed that: the spatial distribution pattern of citrus whitefly in navel orange orchard was aggregation distribution. The sampling technique of citrus whitefly were studied, results showed that random sampling and chessboard sampling were the best methods to evaluate the damage that caused by citrus whitefly. The results of citrus whitefly's life table showed that from egg to adult there was about 73.2d, the duration of egg, 1^st instar larvae, 2^nd instar larvae, 3^rd instar larvae, 4^th instar larvae, pupa was 4.2d, 8.9d, 13.1d, 21.1d, 16.7d respectively; the Exclusion Index of Population Control(EPIC) of egg's, 1^st instar larvae's, 3^rd instar larvae's, 4^th instar larvae's "predated or lost", pupa's "parasitoided" and "disease and others" were higher than other influencing factors, they were 1.238 4, 2.185 3, 1.398 0, 1.296 3, 1.259 0 respectively, they were the import factors to control citrus whitefly population number's increase.The results of using Amblyseius cucumeris Oudemans to control Panonychus citri McGregor showed: according to 1:30, 1:70, 1:150 three proportion to set Amblyseius cucumeris and Panonychus citri on the navel orange young plants in laboratory, 15d later, all the control results of the three dealings were beyond 95%. In the navel orange orchards, using Amblyseius cucumeris to control Panonychus citri, 2 months and 3 months later the controlling results were both beyond 95%, effective and continuing results were attained. Aschersonia aleyrodis Webber was the very important natural enemy, it took an important part in controlling citrus whitefly's population number, the average pathogenicity rate of Aschersonia aleyrodis between August, 2006 and September, 2006 was 35.21%.Using Steinernema carpocapsal All to control the 3^rd instar larvae and pupa of Bactrocera dorsalis (Hendel). toxic regression equation was y=2.394 9+1.077 5x, LD₅₀ and LD₉₅ were 261.63 infective juveniles/ml and 8 794.33 juveniles /ml respectively. As time went on the pathogenicity of Steinernema carpocapsal All became weaker and weaker, it's best to use Steinernema carpocapsal All every 15d in the prevention and cure works. To clean the fallen fruits in orchards could be used to control Bactrocera dorsalis , the effect of this method was that after 7 weeks the rate of fruits protection was 42.82% .