Trajectory analysis on the summer immigrant brown planthoppers(Nilaparvata lugens)in the middle reaches of the Yangtze River captured by aerial net

The possible sources and immigrant pathways of the brown planthopper (BPH),Nilaparvata lugens(St*[l), in the middle reaches of the Yangtze River were investigated by the means of trajectory analysis. The BPHs were captured by aerial nets installed on the plane, which flew at the height of 1 500 meters above the sea level in July 1977, 1978 and 1979. A modified backward trajectory model based on the capturing time, duration time and the synoptic weather data at 850 hPa isobaric level was used to calculate the backward trajectories. The results showed: 1.In the area of northeastern Hunan and southeastern Hubei Province, the immigrant BPHs came from the area between middle Guangxi and middle Hunan Province (24°～28°N,109°～114°E),and there were two immigrant pathways of BPHs:①Liuzhou→Guilin→Hengyang→this area; ②Liuzhou→Guilin→Shaoyang→this area. 2.In the area of eastern Hubei and northern Jiangxi Province, the immigrant BPHs came from the area between middle Guangxi and western Jiangxi Province (24°～29°N,110°～115°E), and there was one immigrant pathway of BPHs: Mengshan→Shuxian→Yichun→this area. 3.In the area of eastern and middle Hunan Province: the immigrant BPHs came from the area between southern Guangxi and southern Hunan Province (23°～27°N, 109°～113°E),and there was one immigrant pathway of BPHs: Nanning→Liuzhou→Guilin→this area. [WTHZ]