The Study On The Influence Of Typhoons On The Migration Patterns Of Planthopper

As one of the major migration pests on rice, planthopper commonly spread in rice-growing areas in southern China, and cause serious damage. The occurrences and regularities of planthopper’s migration are affected with various elements:rice cultivation system, climatic condition, spatial location and the utilization of chemical pesticides will all affect disasters caused by planthopper. Among meteorological factors whice caused by planthopper’s migration dynamic changed, typhoon, as a special and extreme meteorological event, cause many complex and unknown effects to planthopper’s migration, what need further explored. Though divided into different types based on routes, speed, influence region and time, each typhoon has its speciality and non-repetition. Meanwhile planthoppers occuring dynamicly changes according to local weather, planting time of rice and condition of wetness and hotness. These two factors leads to uncertainty of planthopper’s migration and variation. Therefore, analyses on individual cases of typhoon have their value of reference:they are supplement and refinement to the general model on the effect of typhoon to planthopper’s migration. By analyzing the comprehensive effects to planthopper’s migration caused by several typhoons in mid-summer 2012 and the individual effect of typhoon "Fengshen" in early summer 2008, this study provided further understanding on the impact of typhoon to the migration of planthopper. The main contents are as follows:1. Typhoons shape the migration patterns of brown planthopper in the summer of 2012Typhoon can greatly shape the migration pathways and the distribution of immigration areas of ricehoppers. Understanding the effects of successive landing typhoons on ricehopper’s migration dynamics will provide useful information for the inter-regional forecasting. The influence of successive typhoons (1208 Vicente,1209 Saola and 1211 Haikui) in summer of 2012 on migration patterns of brown planthopper (BPH) Nilaparvata lugens (Stal) were studied by trajectory analysis based on light-trap data and NCEP-NCAR reanalyzing data with GrADS and HYSPLIT. The synoptic wind fields and rain belt in eastern China were changed to unfavorable to the northward migration of BPH when the typhoons were approching and after landing, The northward migration passage of the hoppers was broken by the prevailing northeasterly or easterly winds during the typhoons passing, and the fifth northward migration of BPH was obstructed by the continuous strong rainfall, windshear and sinking vertical flow, even though the southly wind was temporarily re-established after typhoon passing. The fifth northward migration process of BPH in 2012 was retarded by unusual typhoon weather, that mitigated the expected serious damage of the hoppers to rice cropping areas in mid and lower Yangtze River basin. The wind fields and rain belt distribution in eastern China during July and early August will probably be an useful index for the forecasting of the BPH damage in mid and lower Yangtze River basin.2. The influence of typhoon 0806 Fengshen on migration of planthopperBy analyzing the typhoon 0806 Fengshen’s influence on rice planthopper’s migration dynamic in 2008,this paper studies the further inland recurving typhoon’s influence on rice planthopper’s migration in every rice producing zone in early summer, and further specified the rice planthopper’s immigration and emigration pattern influenced by this type of typhoon. Of all the typhoons routed near inland in early summer, typhoon circulation influence a wider area of the rice producing zone in south China, the south-west current’s influence on rice planthopper’s north migration is suppressed, and in general, typhoon play a less positive role on rice planthopper’s north migration than south-west current, the superior zone of north migration may be centralized in some rice producing zone of typhoon system. The migration dynamic’s change influence not only on the south China and east China rice producing zone, but also as far as on the mid-west China rice producing zone. Because of the earlier period, the species of immigrated rice planthopper differ in high- 1atitude or the two sides of typhoon circulation rice producing zone caused by the change of the current field, the brown planthopper (BPH) Nilaparvata lugens (Stal)light-trap peak is centralized in Guangdong and Guangxi rice producing zone before typhoon landed and northward flow rice producing zone south-east of the typhoon circulation after typhoon landed, most of the light-trap sites in south China are mixed by two species of rice planthoppers, the small part of Sogatella furcifera (Horvath)light-trap peak is centralized in north and south circulation zone and some part of the single planting rice producing zone after typhoon landed. In the west affected side where the typhoon center can reach, the number of early planthoppers migration may be significantly reduced becaused of the prevailing northerly winds, but the the coastal rice producing area can take advantage of the favorable southwesterly flow and precipitation into inland after typhoon, planthoppers would move northward along the eastern provinces and land centrally, planthoppers moved northly for east china with Typhoon "Fengshen" are mainly from mid-east rice producing area such as Guangdong, planthoppers in Guangxi rice producing area didn’t show a conspicuous north-migration.3. The influence of typhoon transit on planthopper migration patterns in Zhejiang ProvinceBy the research on summer of 2012 typhoon impact on multiple sites in Zhejiang Province, and mesoscale analysis on the planthopper’s migratory dynamics near the center of the typhoon, this paper further clarified the Rice planthoppers’ migration characteristics typhoon brought to Zhejiang’s rice production zone and the landing mechanisms in different structural positions of typhoon. In summer 2012, Zhejiang area is affected by the typhoon, wind direction changes quickly, the position in typhoon structure also changes quickly, by combining the inconsistent Rice planthopper outbreak situation in Zhejiang, result is the typhoon in Zhejiang province promote planthoppers’proliferation, and the warm and moist air may provide better conditions for the survival of rice planthoppers in rice field. Typhoon circulation can provide a good carrier to the migration of planthopper, but generally cause wide range of insect migration landing events; due to the adverse conditions of the typhoon center and cloud wall area inside, the planthopper can’t take off and migration; the edge location area of typhoon cloud wall, due to the airflow convergence in the direction of the typhoon center. When meet the factors such as rain or wind shear etc, causing planthopper centralized landing.