Simulated distribution of occurrence and forecast of Therioaphis trifolii at alfalfa planning region in southern Ningxia, using technique of geographical information system(GIS), referring to established forecast model of T. trifolii :y= 2 298. 017- 21. 754x1 - 47.096x3 + 1. 473x4 (y is the occurrence quantity of T. trifo lii, x1 is June precipitation, x3 is the density of Coccinella septempunctata in the beginning of June, x4 is the cardinal number of the T. trifolii in the beginning of June). Technique of area forecast of T. trifolii which is established based on GIS, can precisely reflect pest occurrence range, distribution of region, area and ratio of different occurrence degree. Forecast result of the technique is intuitive and can be extensive application, after sampling investigation, average accuracy of forecast warring is up to 96.6％.%以宁夏南部山区苜蓿种植区为重点研究区域,运用地理信息系统(GIS)技术,结合所建立的苜蓿斑蚜预测预报模型:y=2 298.017-21.754x1-47.096x3+1.473x4(y:苜蓿斑蚜发生量,x1:6月降水量,x3:6月上旬瓢虫密度,x4:6月上旬苜蓿斑蚜基数),在AroGIs 9.2软件上对宁夏南部山区苜蓿斑蚜进行了发生分布和预测分布模拟.结果表明,所建立的基于"GIS"的苜蓿斑蚜区域化预测预报技术,应用范围广,预测结果直观、精准地反映了宁夏南部山区30万hm2苜蓿斑蚜发生范围,重发区域及不同发生程度的面积和比例,经抽样调查,预警准确率平均达到96.6%.
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