Insect Community Characteristics Of Shandong Tobacco Planting Areas And GIS-based Analysis Of Spatial Distribution Areas Of Tobacco Pests And Natural Enemy

Tobacco is one of the important cash crops. Infestion of insect pests on tobacco can seriously affect the yield and quality of tobacco leaves. This paper studied the species of insect pests and their natural enemies and the community characteristics in tobacco field in Shandong Province. The charts of spatial distribution areas of tobocco main pests and their natural enemies population were portrayed by using the geographic information system(GIS), and the spatial distribution characters were analyzed. All the researches can lay theoretical foundation for forecasting and integrated man agement of pests and conservation of natural enemies in tobacco field. The results were as follows:From 2009 to 2010, insect pests and their natrual enenmies on tobacco in Shandong tobacco areas including Linyi, Rizhao, Weifang, Zibo and Laiwu were surveyed. There were 51 species of insects in tobacco fields, including 32 species of pests and 19 species of natural enemies. The major pests were Myzus persicae(Sulzer), Bemisia tabaci(Gennadius), Trialeurodes vaporariorum(Westwood), Helicoverpa assulta(Guenée)and Helicoverpa armigera(Hübner). The main natural enemies were Aphidius gifuensis Ashmead, lacewings and spiders. Tobacco splitworm, Phthorimaea operculella(Zeller), an quarantine pest, was found in several counties and had a tendancy to spread in the tobacco areas.According to investigation, two-year community characteristics of fourteen counties in Shandong were analyzed. In 2009, insect communities in Zhucheng and Yiyuan had the higher species richness, but in Boshan and Miaoshan with the lower species richness. In 2010, insect communities in the median and later growth period in Yishui had the highest species richness, and in the early growth period the community in Yiyuan and Cangshan had the lowest species richness. Diversity index of most counties was low. It was showed that dominant species of insect communities in the tobacco were prominent and structural stability was poor. The tobacco insect community diversity was related to meteorological factors, surrounding environment(e.g. the surrounding crops and trees), tobacco varieties and man-made factors(e.g. use of pesticides and other field managements).The maps from GIS of population density spatial distribution intuitively showed that occurrence and distribution of tobacco insect pests were region-specific in Linyi tobacco planting areas. Two-year investigation showed the total situation was similar. The occurrence and distribution of closely related species had a certain similarity. The occurence of tobacco aphid and tobacco whitefly was more serious in the south parts than in the north of Linyi, tobacco budworm and cotton bollworm more serious in the north parts than in the south, greenhouse whitefly was serious in the mid-west parts. The splitworm moth mainly occurred in the northern and middle parts of Linyi. Some natrual enemies showed markble synchronization with the pests, and the spatial distribution of nature enemies was in accordance with that of their prey/host insects. The spatial distribution was effected by the differences of climates, geographical sites, base number of pests and other factors.Through analysis of Moran's index I, insect community in Linyi City in 2010, the spatial distribution of the mixed population of tobacco budworm and cotton bollworm during all tobacco growth process showed a positive spatial autocorrelation. Tobacco aphid presented a negative spatial autocorrelation in the early period, but later tended to take on positive spatial autocorrelation. Greenhouse whitefly showed a positive spatial autocorrelation in the early period, but later tended to take on negtive spatial autocorrelation. Standard model pictured of the positive spatial autocorrelation presents"hight-hight"or"low-low"spatial distribution pattern, and the negative spatial autocorrelation presents"hight-low"spatial distribution pattern, which corresponded with the population density spatial distribution maps from GIS 9.2. The spatial distribution of the main insect pest populations existed spatial autocorrelation. But the standardized Z value were between -1.96 and 1.96(p=0.95), showing the autocorrelation was not significant. The spatial dynamic of the insect pests were affected by pest behaviors, natural enemies, environment factors and the distribution regions of the pests.