Sources Areas And Landing Mechanism Analysis Of Early Immigratory Sogatella Furciffra(Horváth) In Southeastern And Northeastrn Yunnan

The white-backed planthopper(WBPH),Sogatella furcifera(Horvath)and the brown planthopper(BPH),Nilaparvata lugens(Stal)are major migratory pests on the rice,pose the huge threaten on rice production in several countries.Since 2005,outbreaks of BPH occurrence again in China,and the threat caused by RPH continued in the following years.Not only in the east of China,but also in southwest areas exist the huge loss on the rice field which caused by rice planthopper in the year of 2007,2009 and 2012.The hoppers occurred in Yunnan rice field is not optimistic simultaneously.Previous studies in WBPH and BPH of eastern China have reached a depth and breadth level,and obtained certain achievements more or less.However the fundamental research of flyways and rules of rice planthopper in Yunnan are still exist many problems to be solved.The lack of systematic study on source areas problem,and the landing mechanism of rice planthopper in Yunnan have always existed.In this paper,though analysis each main light-trap catches and corresponding meteorological conditions of WBPH in southeast Yunnan during April to May from 2008 to 2012 and northeast Yunnan during May to Jun in 2009,2010 and 2012,the distribution range of sources areas in early immigrating WBPH of southeast Yunnan is clear,and the early immigration characteristic of WBPH in northeast Yunnan is also realized.Though comparative analysis inter-annual distribution range of sources areas and landing mechanism,indicate that occurrence of rice planthopper exist unique characteristics.The main research results are as follows1.Initial source and landing mechanism of early emigrating WBPH in southeast YunnanBy trajectory analyze,field survey data and homologous meteorological data of emigrating peak which happened on April and May during 2008 to 2012 in Funing,Malipo,Qiubei and Guangnan,several results are received:Inter-annual difference of sources areas distribution during 2008 to 2012 is not sharp,north and north-central Vietnam,northern Laos are major sources area;northern and northeast Myanmar,western and southwest Yunnan are partial sources area.However 2010 is special,northern Myanmar,western and southwest Yunnan are major sources areas.Funing as an example to analysis distribution of sources areas in April and May,the result is that sources areas are different between April and May.In April,Buma and Golden Triangle area are major sources area;In May,north and north-central Vietnam?northern Laos are major sources area,moreover eastern Myanmar?western and southwest Yunnan are partial sources area.Landing mechanism of 349 emigrating peaks of WBPH in four sites were analysised,wind shears occupied 75.39%,low temperature barrier occupied 56.45%,precipitation occupied 31.81%,downdraft occupied 25.21%.There are several differences in the mechanisms among inter-annual.wind shears,low temperature barrier,precipitation and downdraft are meteorological factors which lead to concentrate landing of WBPH,and the wind shears exist in each landing incident,the low temperature barrier is irreplaceable factor in landing incident,moreover rainfall happen follow closed the wind shears and temperature reduction almost every time,these three factors cooperation together to impel the hoppers landing.In individual years,precipitation and downdraft plays an important role in landing incidents as well as temperature barrier.2.Initial source and landing mechanism of WBPH in northeast YunnanYiliang is an appropriate example to clarify the source problem and landing mechanism of the early immigration WBPH in northeast Yunnan.According to trajectory analyze,field survey data and light-trap catches in other site of WBPH during May to Jun,the distribution of source areas were show:In May,the central and southern Yunnan are major sources areas;In Jun,the central and southern Yunnan,central and western Guizhou and southeast Sichuan Basin are major sources areas.Though frequency statistics of homologous meteorological during light-trap peaks,several results are obtained:The wind shears exist in each landing incident,low temperature barrier and precipitation account for more than half,and low temperature barrier have the greatest impact in May,precipitation mainly concentrated on the Jun.Low temperature barrier and precipitation are two big factors for landing of WBPH in Yiliang.