| The rice leaf roller, Cnaphalocrocis medinalis Guenée, and rice planthopper are the major crop peststhat cause serious damage to rice production. Xing'an, in northeast Guangxi Municipality, is the keyannual migratory route for the rice leaf roller and the rice planthopper migrating back and forthbetween southern and northern China. Recent years, the rice cultivation system changed to single anddouble mixed rice system. A better understanding of the population dynamics, populationcharacteristics and migration trajectory, explicit the effect of the a scale planting of middle seasonrice on the population dynamics and the migration trajectory of the two migration pests will bebeneficial for the monitoring, warning and long-term control of these pest in Xingan and in China. Inthis study, light traps, systematic field surveys, and dissection of female ovaries were used to studythe population population dynamics and population characteristics of these pests. The spatio temporaldistribution of source areas of C. medinalis early migration peaks and source areas and landing areasof BPH miagration peaks in2011were analyzed using HYSPLIT (Hybrid Single-Particle LagrangianIntegrated Trajectory), a software package that simulates migration trajectories, and GrADS (GridAnalysis and Display System), a program for analyzing and displaying the synoptic meteorologybackground during the migration periods. The spatial distribution of BPH in middle season rice wasanalysised by traditional spatial analysis method and Geographic Information System. A emmigrateprogress of C. medinalis monitored by the millmetircs scanning entomological radar in2007wasreanalysised in this paper. Forecast of the occurrence period and occurrence quantity were studied bystepwise regression method and artificial neural network. The results were as follows:1. The vertical pointing searchlight-trap could monitor the population dynamics of C. medinaliseffectively.It could catch much more moths than Jiaduo light trap, including the immigration, passingand emigration airborne populations of C. medinalis. So that the peaks of catches on the two kinds oftraps and the ovarian developmental level of the female in the vertical pointing searchlight-trap wouldbe able to determine the characteristics of C. medinalis. According to this method, three case studiesof immigration, passing and emigration airborne populations of C. medinalis were conducted in thispaper.2. The population dynamics of C. medinalis varied seasonally in Xing'an. C. medinalis had sixgenerations a year, namely the2nd-7thgeneration. The3rd-5thwere the major pestilent generation.Each of the three annual rice crops (early double-crop, middle-season single-crop, and latedouble-crop) experienced three generations of C. medinalis, with some overlap of leaf rollergenerations onto more than one crop. The population density of C. medinalis in the early double-croprice field was significantly higher than in other two rice fields. The ratio of mated females and theratio of females with matured ovaries indicated that the second and third generations which mainlyinfested early rice, were immigrants. The fourth generation, which also mainly infested early rice, emerged locally and partly from immigration population. The fifth generation mainly infestedmiddle-season rice and were mostly locally emergent, but with some immigration and someemigration. The sixth generation was mostly emigrants. The early sixth generation infestedmiddle-season rice, while the late sixth generation infested late rice. The seventh generation, mainlyinfested late rice and were basically emigrants. The middle-season rice which largely planntedbecame the trasitional brige between the early and late rice. It caused C. medinalis settled down andinfested middle-season rice.3. The early immigration amont and immigration peaks were different among years. The biggestimmigration peak postponed with years. The occurance time of partial northern air stream on800hPaisobaric was the main reason caused these differences. Most of the immigrants in May came fromsoutheast of GuangXi and southwest of Guangdong, and the immigrants in June came from southeastof GuangXi, southwest of Guangdong and north of Hainan.Analysis of weather conditions during themigration peaks showed that strong southwest and partial southlow-level jets carried massivenumbers of C. medinalis into Xing'an, while heavy rainfall caused mass descent.4. The flight parameters of C. medinalis in sounthern China were different form that in eastern China.C. medinalis started take-off behind30min of sunset, reached the take-off peak at about20:00,take-off can last1-1.5h. C.medinalis generally flew below1000m It accumulate and form2-3layersdense layers when flew. The biggest density was at400-500m. The insect layer was coincide closelywith partial maximum wind speed and was not conincide with wind direction. However, the biggestdensity was not always at the height of biggest wind speed.5. The single and double mixed rice system in Xing'an was beneficial for the accumulation andincrement of BPH. The BPH whose peak period of occurance was coincidence with themiddle-season rice growth period, not only caused serious damage to middle-season rice, but alsoaccumulated pest source for late rice. The immigrants to Xing'an in2011mainly came from southeastof GuangXi, southwest of Guangdong and coastal area of Hainan. The autumn immigrants camefrome the southwest of Hunan and west of Jiangxi. In October local emigrants mainly flew to themiddle of Guangxi, some population which flew to the south of Guizhou can not survive because oflacking food. Partial southlow-level jets carried massive numbers of BPH into Xing'an, while heavyrainfall caused mass descent.6. The spatial distribution of the adult and larva mixed population, the macropterous adult populationand the larva population were mainly aggregation distribution in middle-season rice, except ofuniform distribution and random distribution in early stage, because of less density of BPH.Aggregation intensity increased as the population density increased. The aggregation center changedwith time. There were1or sevel aggregation center in field, generally showed middleaggregation—west and east extending—middle aggregation—west and east extending.7. Forecast of the occurrence period and occurrence quantity were studied by stepwise regressionmethod and artificial neural network. The historical coincidence of stepwise regression method was80-87.5%, while forecast accuracy was75-80%. The historical coincidence of artificial neural network was100%, while forecast accuracy was75-100%. So, screening forcast factories by stepwiseregression method, then forecast by artificial neural network was a good forecast methed.
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