The Migratory Dynamics Of Sogatella Furcifera(Horv(?)th)and Nilaparvata Lugens(St(?)l)in Vietnam

Vietnam is located in the east of Indochina,Southeast Asia region,adjacent to the China border in the north,Laos and Cambodia borders in the west,Gulf of Thailand border in the southwest,East Sea border in the east and south.Vietnam has an area of 331.212 km2,including 10.150.000 ha of top soil,7.750.000 ha for rice cultivation;long and narrow topography toward north-south direction with the length of 1.650 km.Plain area accounts for one third of the territory,which is mainly distributed in the Red River delta and the Mekong delta.Based on the topography,soil and climate conditions,references on agricultural development history,Vietnam is divided into 8 different agricultural ecology zones in the direction from north to south:Northeast,Northwest,Red River Delta,North Central,Central Coast,Highlands,Southeast,and Mekong Delta.In Vietnam,there are 2-3 times for cropping rice depending on ecological zones.In the North,there are often two times in the Winter-Spring season and Summer-Autumn season(Hanoi capital,Nam Dinh,Hai Phong province,etc.);and there are often three rice cropping seasons in the South:Winter-Spring,Spring-Summer and Summer-Autumn,where rice will be cultivated almost all the time.Brown planthopper(BPH),Nilaparvata lugens(Stal)and white-backed planthopper(WBPH)Sogatella furcifera(Horvath)are important and dangerous pests for rice plants in Asia.Hoppers are commonly distributed in the west of Asia,Southeast Asia,South Asia,North of Australia,Pacific island,Egypt and rice planting countries,and their movements in the year seriously threaten rice caring.In Vietnam,BPH and WBPH are distributed in all rice planting areas.In North and Central regions,Hoppers cause harm mainly in the main Winter Spring season and late season and the main time for doing harm is April-May and August-September.In the South areas,Hoppers cause harm mainly in the main Winter Spring season and main Summer Autumn season and the main time for doing harm is April-May and September-October.As the changes of cultivation level,variety distribution,hopper resistance to pesticides and their movements,the damage of ricehoppers to rice planting areas become more and more serious,causing great decrease in productivity and output of these areas.The migration processes and environmental factors that impact on immigration of rice hoppers in Vietnam were studied by simulation methods using ArcGIS,WRF,GrADS,HYSPLIT based on the field survey data,light trap catches of the hoppers,and general data on weather and geographic information.The results of this thesis are mainly as follows:(1)The dominant winds in Guangdong province,China,in 2006-2011 were northeasterly,therefore the rice hoppers in Guangdong moved together with the wind to Vietnam and Indochina.BPH in rice planting areas in Guangdong province moved and landed mainly in the North and the Central of Vietnam and some moved to Laos,Thailand,Cambodia and other countries in Southeast Asia.(2)Through the spatial analysis of the hoppers distribution from some high-density regions in Northern Vietnam in March,it has been found that:in the Northeast of Vietnam,ricehoppers(BPH,WPH)were mainly immigrated from the northern Laos,others from Gold Triangle area,southern Laos,South plain of Vietnam and southern Hainan province,China;in the Northwest of Vietnam,ricehoppers were mainly moved from the Central of Myanmar,Gold Triangle area,northeast of Thailand and south of Laos areas.Moreover,a part of hoppers into Northwestern Vietnam were from the Central Thailand,Southern Central Laos,the Central Vietnam and southern Hainan,China;in the Red River delta,the source hopper populations were originated from Northeastern Thailand and the Southern Central Laos;and some of them were from the rice planting areas in eastern Myanmar,northern Thailand,Central Vietnam and southern Hainan,China;in the Central Northern Vietnam,hoppers were mainly migrated from the Central and northeastern Thailand and the Southern Central Laos;and part of them were from southern Laos,Central Vietnam and Hainan province,China.(3)From March 23 to May 20,2013,BPH populations in Winter Spring season in Son Trach district,Quang Binh province,Vietnam were emigrated and landed to rice planting areas in Northern Vietnam,and Southern China.(4)From late February of 2003 to March of 2014,BPH populations in southern provinces of Vietnam(Quangnam,Quangngai and Binhbinh province)moved and landed to rice planting areas in Northern Vietnam and Southern China.(5)In Mekong Delta,different developmental stages of rice could be seen in the paddy fields in February and March in 2012-2014,that provided a favorable food source for rice hoppers.And during the season,the dominant east and northeast winds with low speed would not be able to carry the hoppers to perform long distance migration.The results of trajectory analysis showed that the ricehoppers in Mekong Delta mainly moved in short distance and landed within the southern Indochina.The results of our study illustrated that,hoppers in Mekong Delta could not move directly to rice planting areas of China,but they will immigrate into Southeastern Vietnam,Central Coastal rice cropping areas of Vietnam,the southern coast of Cambodia,Southwestern Thailand and Southeastern Myanmar...