| Brown Planthopper (BPH, Nilaparvata lugens (Stal)) is one of the most serious pests of rice in both temperate and tropical regions of East and South Asia. Since1970s, it has become especially problematic and resulted in a broad and significant reduction in rice yield. Then it occurred lighter in early1990s, and outbreak more often after2000. The certainty of meso-and micro-scale source areas and the regulation of outbreak of BPH are very important for remote prediction and scientific prevention and treatment.Firstly, the ovarian morphological change and grading criteria of BPH were identified by ovarian dissection so that better using forest forecasting. Then the regulation of light-trap population and the source areas of brown planthopper (BPH) in the Yangtze River Delta were examined in this paper. The regulation of outbreak was investigated by the data during2003-2010, and the case study in2007was analyzed on the source area, weather background of light-trap peak days and outbreak mechanism.1The morphological changing processes and grading criteria of ovarian development of BPHFifth instar nymphs of BPH were raised in singles with rice of booting stage under temperature25℃, relative humidity of75%and photoperiod16L:10D conditions in the test tube with20cm×2cm. Dissecting the female adult BPH in different ages in hours, and photographing the ovarian.On the basis of existing research, the grading criteria were clear and definite. The results were as follows:white ovariole pluses emerging in lateral calyx or not was the obvious grading standard of level I and level II. The oocytes maturing or not was the grading standard of level II and level III. In the late stage of level III, the mature eggs arranged in neat, and the base part of ovarioles were hollow or mature oocytes in level Ⅳ. The ovarioles were hollow or shrink in level V. 2. The study on light-trap population of BPH in the Yangtze River DeltaThe regulation of light-trap populations were studied using the light-trap data of Fengxian, Tongzhou, Wujin, Shaoxing and Jiaxing from1977-2010. The result indicated that:the numbers of light trap of each generation were large during1977-1991, the numbers of light trap of each generation were light during1992-2004, the numbers of first and second generation were light but the numbers of third generation were large in some years, especially in2005and2006. The average of first appearance time is June28. The most average of first appearance time occurred in late June, and then in early July and middle June. Main peak days were most in middle July, but the peak days in late August were obvious more than other periods in2005-2010. The quantities of migration and the numbers of peak days were correlative with the degree of occurrence of BPH in the Yangtze River Delta, but the first appearance time has no correlation with the occurrence degree.3. The source areas of BPH in the Yangtze River DeltaThe source areas of BPH before September10were analyzed in the Yangtze River Delta represented by Fengxian, Tongzou, Wujin, Shaoxing and Jiaxing through HYSPLIT trajectory analysis platform. From middle June to early August, the source areas were from south Guangdong and south Guangxi to Hunan and Jiangxi in the northeast-southwest direction. The source areas during middle August to early September were complex:the south Anhui and north Jiangxi with the early mature single cropping rice were mainly the source areas, and a little were also from local areas and Zhejiang Province.In different occurrence degree years, the sources are different:the source areas of the first generation in outbreak years were mainly in north Guangdong, north Guangxi, south Hunan and south Jiangxi, with early mature double cropping rice could support large adults BPH. The source areas in light or moderate years were more dispersive. The source areas of the second generation were similar in different occurrences, namely in a northeast-southwest zone including Guangxi, Hunan, Jiangxi, Anhui. The source areas of the third generation were different in different occurrences, and they were mainly from south Anhui, northeeast Jiangxi and west Zhejiang in the outbreak years.The34years were divided into3periods according to the occurrence and national rice plant system:1977-1991,1992-2004, and2005-2010. The source areas of each period were as follows:the source areas of the first generation were most from north Guangdong, north Guangxi, south Hunan and south Jiangxi before, whereas the regulation was not obvious since1992. The source areas of the second generation were mainly in Hunan and Jiangxi before1991, and most in nearly areas such as Anhui in light occurrence years. The source areas of the third generation before1990s were mainly local populations because there were not many emigrations populations and the local populations were large. Since2005, the peaks and numbers of the first and second generations were few, and the source areas were most from Anhui and Jiangxi. The source areas of the third generation were mainly in south Anhui and north Jiangxi in which plant the early mature single cropping rice.There light trap numbers of ten-days and occurrence degrees of BPH in the Yangtze River Delta were correlated with light trap numbers of ten-days in the source areas respectively:light trap numbers of local area were correlated with Guiyang, Qujiang, Ji’an and Fuqing from middle July to early August, and with Dongzhi, Huizhou and Ji’an from middle August to early September. The correlation of Huizhou was most obvious, and was significant or very significant in early and middle July, early and middle August and early September. It indicated that the light trap numbers in source areas had forewarning function for the light trap number and occurrence degrees in the Yangtze River Delta.4The outbreak of BPH in the Yangtze River DeltaThe outbreak of BPH was related with the late migration and high increase rate using chi-square analysis, trough the field and light trap data in Chongming, Danyang, Jingjiang, Zhangjiagang and Jiaxing during2003-2010. There were more late migrations when more west or northwest wind direction happened, and the numbers of late migration were impacted by the occurrence of BPH in the source areas. If there was no migration in late stage, the higher autumn temperatures were more in favor of reproduce of BPH and outbreak in late September.5. The case study of BPH in the Yangtze River Delta in2007The source areas and landing mechanism were studied and through the light trap data and field data in Nanhui, Danyang, Zhangjiagang, Jiaxing and Huzhou. The results showed that:the source areas during June27-30were mainly in middle and south Jiangxi and north Guangdong. The source areas during July18-20were mainly in south Anhui, north Jiangxi, east Hunan and northeast Guangxi, which were more west than during June27-30. The twice migrations both occurred with low-level jet at850hPa when the subtropical high moved towards west and north. The first migration was landing with plum rain in Jianghuai region when the north cold air mixed with the warm and wet air from southwest. The second migration occurred in the subtropical high region with more down draft, and the wind speed was low. The migration during August21-22was affected by the peripheral inverted trough of the Tropical Storm "Sepat". The southwest wind switched to south with the lower speed and favor for landing. The subtropical high moved toward east and weakened, and many shortwave troughs moved eastward. The west wind at850hPa altitude and the intermittent precipitation were the suitable weather for BPH migration. The source areas were from middle Anhui and north Jiangxi. The forward trajectories from Huaining in south Anhui indicated the landing areas were the Yangtze River Delta. At this stage, there were adult peaks of BPH in early mature single cropping rice, so the south Anhui was the source areas of the Yangtze River Delta.The population increase rates of BPH with the initial generation to the second generation and with the second generation to the third generation were lower than the historical average. The population increase rates with the second generation to the third generation were higher than the historical average. It related to "hot summer and warm autumn". The hot summer weather would suppress the BPH reproduce, so that the population size was small in early stage. Although there was some late migration and the warmer autumn, the populations were not outbreak in large regions. |
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