Huizhou, due to its particular geographic situation, is located at the important routes for both northward and southward migration of White-Backed Planthopper (WBPH), Sogatella furcifera (Horváth). It is of significant importance to analyze its population dynamics and population characteristics for the forecast and control of WBPH in southern Anhui Province and even in all Yangtze-Huaihe regions. Therefore, the spatial distributions of source populations of immigrated WBPH in different generations, the weather backgrounds and landing mechanisms of the major immigration events in 2009 were explored through long term field survey, ovary dissection of macropterous female and trajectory analysis under HYSPLIT, ArcGIS and GrADS.
The results were as follows. The 3^rd generation of WBPH severely damaged single cropping mid rice (the maximum: 3985 hoppers per 100 hills) and double cropping late-season rice (the maximum: 17470 hoppers per 100 hills) in Huizhou in 2009. The population was kept at low level from the 4^th to the 5^th generation,. The proportion of immature ovaries (gradeⅠ-Ⅱ) of WBPH from the 2^nd to the 4^th generation in mid rice fields were 89.74%, 89.95% and 100%, respectively, indicating the typical emigration type. The macropterous adults would migrate to Yangtze-Huaihe region or disperse to local late rice field during the period of 2^nd and the 3^rd generation. While in the late 3^rd generation (2nd-19th August), some of WBPH returned from Yangtze-Huaihe region would immigrate to Huizhou. In double cropping late-season rice fields, the proportion of immature ovaries (grade Ⅰ-Ⅱ) from the 3^rd to the 5^th generation were 35.09%, 86.42%, 89.47%, respectively, suggesting most of the 3^rd generation WBPH would be immigration type, while the 4^th and the 5^th generation basically belonged to emigration type.The appearance of horizontal wind shear, downdraft and heavy precipitation could be the synoptic background for prediction of the migration of WBPH in Huizhou. During the first immigration peak (29th June-3rd July), the quasi-stationary front and heavy rainfall, which were caused by the southwest low level jet jointed with northern cold air, induced the immigration of WBPH in the mid and lower reaches of Yangtze river. The downdraft in southern Anhui Province forced the concentrated airborne WBPH to land in Huizhou from 19^th to 22^th of July, and the immigration from 25th-27th July was formed by a cyclone and the heavy precipitation. Trajectory analysis of the source areas of each generation showed that most of the immigrants came from the southern Hunan Province, the central and southern Jiangxi Province.