| Insect community structure characters of GAP leaf-picking ginkgo plantation, population dynamics of Scirtothrips dorsalis and its natural enemies, spatial distribution pattern of the thrip, the physical and chemical control for the thrip were studied from 2008 to 2010 to provide technical support for producing good quality ginkgo leaves for exportation agaist the foreign technological barrier and increasing foreign exchange earning in Tancheng County, Shandong Province,China.Twenty-two species of insects including five species of pests, sixteen species of natural enemies and one species of neutral insect were investigated on the canopies of GAP leaf-picking ginkgo trees. In the insect community, as the major target pest, Scirtothrips dorsalis with the maximum number dominance was the dominant species damaging the ginkgo leaves seriously. The spider, Hylyphantes graminicola, with the maximum number dominance among all the natural enemies was the dominant one attacking the thrips. The temporal structure pattern of the insect community in the ginkgo plantation was analyzed by the optimal sorting method and grouped into four continous periods. The occurrence characteristics of these pests and nature enemies in each temporal period were analyzed. The temporal pattern analysis can lay a scientific theoratical basis for controlling the thrip and conserving its many natural enemies.The population dynamics of Scirtothris dorsalis and its main nature enemies were studied in detail. The results showed that the spiders, especially Hylyphantes graminicola among all the nature enemies, synchronized the occurrence of the thrips, showing that the spider is an important natural control factor. In addition, ladybirds, lacewings and Orius minitus could play an important role in controlling the thrip alltogather.The spatial distribution pattern of Scirtothrips dorsalis in GAP leaf-picking ginkgo plantation belonged to negative binomial distribution. The reason for the thrip aggregation arose from some environmental factors. The number of the thrip distributed significantly differently in different parts of ginkgo canopies and in different periods. In June, the sequence of population sizes of the thrip was the lower parts > the middle parts > the upper parts, but in July (near the harvest), the sequence was the upper parts >the middle parts > the lower parts. Scirtothrips dorsalis have significantly different taxis to different color board traps. The blue one was the most favorite for the thrips. The taxis sequence of the thrip to other color board traps was white, green, yellow, grey and red in turn. Different suspension ways of blue board traps can affect the trapping effectveness of the thrips. The best way of trapping thrip was that the blue board traps with their lower margin were hung 15cm above and away from the top of the canopies of ginkgo trees. The trials showed that blue traps could give very good control effeciveness for the thrips from 44% to 75% in GAP leaf-picking ginkgo plantation, especially used in early period of the growing season of the ginkgo.The effective and non-pullotant insecticdes for controlling Scirtothrips dorsalis were screened, which were matrine and rotenone (two botanical insecticides), spinosad (one insect-killing antibiotics), and imidacloprid (one physiological selective insecticides). According as the 3 and 4 instar nymphs of the thrips crawl from ginkgo trees into the soil and pupate, phoxim, an organophosphrous insecticide with lower toxity, with irrigation was applied into the soil, good control efficacy was obtained.The economic, ecological and social benefits brought by use of physical and chemical control of the thrip were tentatively analyzed in this paper. |
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