The Study On Oversea Source Area Of Nilaparvata Lugens (Stal) And Sogatella Furcifera (Horvath) In China

Rice planthoppper, including brown planthopper (BPH), Nilaparvata lugens (Stal), and white-backed planthopper (WBPH), Sogatella furcifera (Horvath), were major harmful rice pests in Southeast and East Asia, and can migrated long distance, In the past5years, problems from both two species of planthopper have intensified in several countries again, such as China, Thailand, and Vietnam, which cause the huge loss on rice production,In2005, outbreaks of BPH occurrence again in China and other countries of Indochina Peninsula, and the threat cause by BPH continued in the following years, In2007, another worst year on record, severe damage extended in southwest of China specially Yunnan province. In addition, there is mass immigration of WBPH in South Yunnan in2009, not only the light-catches numbers much more than2007, and the main immigration peak time was one month earlier than2007. We want to know Where the WBPH immigrants come from and what reason cause the mass landing in2007&2009.South China suffered the snowing and freezing Disaster in spring,2008, and the north limits of over-winter by WBPH and BPH were in19°, but immigration peak of WBPH appeared in Gulf Qin Zhou (to the south of21.94°N) and Lei Zhou Peninsula (to the south of23.43°N) in lat Mar,2008. And another huge immigration peak was been recorded in Qinzhou Gulf in9to11April,2008.Since1960’s, the records of BPH outbreaks in China and Indochina Peninsula indicated that the time of BPH outbreak appeared simultaneous and temporal delay. We want known if the BPH populations have exchange with the populations of mainland in China.The migration behavior of BPH and WBPH is the key factor that limited the effective management all over the Asia. China lies in temperate area, the over-winter area of BPH and WBPH is little, all infestations at high latitudes because of the immigrants from Indochina Peninsula. The initial source area of WBPH and BPH immigrated into China was remain unclear. After immigration of BPH and WBPH into China in early spring, accurate migration route of BPH and WBPH between rice production areas in China still need to be studied. The oversea source area of WBPH and BPH in China were examined in this paper, including the early migration in Yunnan in2009&2007(chapter2), Qinzhou in2008(chapter3), Fujian in2007&2010(chapter4). In addition, the migration route of WBPH and BPH were been drawn between Indochina Peninsula and South of China.The major findings are as follows:1. the initial resource area of WBPH and BPH in China1) The source areas of early immigration of WBPH from April to May2009in5research spots of Yunnan were studied through the daily light-trap catches, field surveys, immigration trajectory simulation and meteorological background analysis. The results showed:(1) The main source areas of the early immigration of WBPH in2009were located in Myanmar, and the secondary source area was at the Laos and "Vietnam, only a few came from Imphal of India.(2) The ceiling of the threshold temperature of flying WBPH in atmosphere and the wind shear associated with heavy precipitation were the main impact factors for the concentrated landing of WBPH.(3) The high frequency of westerly and the great increasing of rice planting area in the source areas of Myanmar were the principal reasons, which caused the mass immigration of WBPH to Yunnan.2) There are different initial source of WBPH in Jiangcheng between2007and2009. In2007, the largest immigrants’peak appeared in May, and the main source area located in South Myanmar and Golden Triangle. The major immigrants peaks take place in April and came from central Myanmar and north Myanmar in2009. There are small peaks on lamp in2008.3) There are different initial source of WBPH between Jiangcheng and Xichou, in past3years. Jiangcheng lie in southwest of Yunnan province, and mass immigrants were come from Myanmar and Golden Triangle. However, Xichou lie in southeast of Yunnan, and the main source area located in North of Vietnam.4) The central region of Vietnam offered the main numbers of WBPH to Qinzhou, Guangxi Zhuang Autonomous Region on April2008. The12h endpoints of backwards were located in Hainan Island. Only a few endpoints of24h and35h were come from Northeast and north of Thailand. In addition, High temperature was an affected factor for the concentrated landing of WBPH in April2008in Qinzhou.5) Guangdong and Hainan were the main source area of RPH immigration peaks occurred from mid May to June2007and2010, in Fujian province.(1)The mass immigrations have little significant correlation with the original source areas of WBPH. in the Indochina Peninsula, but were triggered by the continuous rainfall and the outbreaking population of the2nd generation RPH in southern China. The earlier mass immigration population of WBPH occurred from mid May to early June of2007and2010had exhibited the similar source area:mostly from Guangdong, and Hainan province, had no trajectory from the southeast, Philippines.(2) The co-occurrence of low-level jet and continuous rainfall directly caused the concentration of the airborne migrants and the mass immigration of WBPH. During the appearance of major immigrants on May to June2007and2010, there were strong southwest low-level jets at850hPa simultaneously. Meanwhile, the West Pacific subtropical high was stronger than normal and extended towards west, and the northern jump of its ridge postponed, that caused the formation of a stationary front in south China and brought the sustained rainfall.(3) The increasing of the population of the2nd generation rice planthoppers in Guangdong, Guangxi and Hainan during mid May to early June in2007and2010was the underlying reason for mass immigration in Fujian province, which was bred by the early-immigration of the1st generation in those source areas in April to early May.2. The study on migration route of BPH in central of Thailand in2009There are no exchange of BPH population between the central Thailand and mainland of China. In March and April, Thailand were controlled by subtropical high-pressure, the wind speed cannot exceed5m/s at850hPa, which have no use to assistant the insect long-migration. In Jun and July, with increasing frequency of low-level jet, the e migrated distance increasing, in July and August. West airflow control the whose Thailand, the emigration population only to south of Laos and central of Vietnam with west airflows. Thus, the generation of the immigrants migrated to South of China next year.3. migration route of BPH and WBPH in Indochina PeninsulaAccording the results of the first five chapters, incorporated the31years statistics data (1979-2009) on airflow directions at850hPa in Indochina Peninsula, we obtain the following conclusions:(1) Myanmar is the most important source area of WBPH immigrated to northwest of Yunnan, and the Golden Triangle region in second place. After mid May, planthopper immigrants occurred in southeast Yunnan were provided by the North Vietnam.(2) The central region of Vietnam is the main source area of Guangxi Zhuang Autonomous Region in March and April.(3) The Red River Delta provided emigration population to main China, such as Yunnan and Guangxi, only in late May.(4) The possibility exists an annual cycle of BPH population between Thailand and China. BPH from Thailand have gene exchange with the ones from Laos, Vietnam and Cambodia, by eastwards airflow in spring and westwards airflow in winter each year. Indirect exchanges of BPH population were occurrences that BPH from Thailand immigrated to Laos, Vietnam during Jun to August each year, and then whose offspring migrated to China in spring in the next year.