Abstract:Since the 1990s, the rice planting system has changed in different degrees with transferring two-season farming rice to one-season rice in north rice region of south of the Yangtze River (including Jiangsu, Zhejiang, Anhui, Jiangxi, Hunan, Hubei provinces). In order to illustrate the effect of the change of rice planting system on the formation of outbreak population of Nilaparvata lugens (Stl) (BPH), the population dynamics and characteristics of the pest in the single-cropping middle-season rice fields and double-cropping late-season rice fields were studied in Huaining and Qianshan in 2007, 2008 and compared through systematic field survey and female ovarian dissection. The results showed that after planting single-cropping rice in large areas in Anqing, the immigrant population of BPH during middle June to late July could migrate into the paddy fields of single-cropping rice directly and reproduce continuously, which greatly enhanced the population proliferation times of BPH as high as several hundred times, and the population density of BPH in single-cropping middle-season rice fields was higher than that in double-cropping late-season rice fields. The population characteristics of BPH for each generation in single-cropping middle-season rice fields and double-cropping late-season rice fields showed that the peak emigration exhibited from late August to middle September in single-cropping middle-season rice might act as one of the population source area, which would be either to emigrate in long distance to Yangtze River Delta or transfer in short distance to the double-cropping late-season rice locally. So the change of the double-cropping rice planting system to the single-cropping rice not only significantly increased the local population size, but also directly caused the mass occurrence of late immigration at Yangtze River Delta rice areas in recent years. Therefore, the change of rice planting system was beneficial for the formation of outbreak population of BPH.