Abstract:  A typical great migration event of rice leaf folder, Cnaphalocrocis medinalis (Guenée), occurred in rice region of southern China and south part of southern Yangtze River during June 10-12, 2010. In order to illustrate the population characteristics of the pest and further reveal the atmospheric dynamic mechanisms of large-scale immigration of C. medinalis, the migration process of C. medinalis and the atmospheric backgrounds that influenced the landing process were analyzed by using HYSPLIT, a trajectory analysis software for the simulation of migration trajectories, GIS (Geographic Information System) and GrADS (Grid Analysis and Display System). We obtained the following results: (1) The population of C. medinalis in northern Guangdong resulted mainly from immigrations, but supplemented by a little local breeding. (2) Southwest of strong low-level jets carried large-scale invasions of C. medinalis into Guangdong. The involuntary landing populations of C. medinalis were caused by rainfall, the immigrants of C. medinalis landed obviously on the marginal rainfall zone such as Qujiang District, Zijin County and Fogang Couty, and the differences of the spatial distribution of the rainfall zone directly resulted in the significant differences of C. medinalis population densities that landed at Qujiang District and Nanxiong City. (3) Simulations of migration trajectories indicated that most of the immigrants came from south-western Guangdong. The double-cropped early season rice of this area with Yangchun City as the representative was in the reproductive stage in early June (flowering and filling stage to milk stage), which was deteriorative for C. medinalis as food, so this area could provide a great amount of emigration moths of C. medinalis to form the large-scale invasion into northern Guangdong.

Key words: Cnaphalocrocis medinalis, migration, population characteristics, low-level jets, trajectory analysis, insect source area