| Brown planthopper(BPH),Nilaparvata lugens(St?l)is a long-distance migratory pest that likes warmth and moisture,especially affected by temperature and rainfall.The southern rice region of China is the main hazard area of BPH,and the impact of rainfall on the migration of BPH in southern China can provide a scientific basis for forecasting the meteorological conditions for the migration of BPH,and further improving the early warning ability of BPH.Based on the BPH lamp lure data of 105 plant protection stations in southern rice-growing region from 2006 to 2016 and the daily rainfall data of 720 ground conventional meteorological stations,15 representative pest detection sites were selected,A series of analyses were performed on the characteristics of rainfall influencing the migration of BPH by using ArcGIS spatial analysis tools and SPSS statistical software,and screened the case of the special rainfall type acting on the immigration peak..The weather background was analyzed by NCL software,combined with the WRF model,the mechanism of the influence of rainfall on the migration of BPH was analyzed.The main findings of the study are as follows:(1)During the period of migration,the spatial distribution of the infested population of BPH in southern China was in good agreement with the spatial distribution of rainfall.The increase of rainfall days and rainfall was conducive to the significant migration process of BPH.Due to the complexity of the factors such as the number of insect populations in the insect source area,the background of the atmospheric circulation,and the ecological environment of the worm-reducing area,the inconsistency of the two insects may occur in the case of large occurrences of individual pests or individual rainfall years.(2)According to the interannual change sequence of insect amount and rainfall in the migrating season,the insect amount and rainfall fluctuation in the rice area were basically the same over the years,but the change of the BPH was unstable under the influence of rainfall during the northward migration.The reason is that summer is the period of frequent rainfall in China,and the frequency of strong convective weather is high.Short-term heavy rainfall often occurs,because the spatial and temporal heterogeneity of precipitation distribution leads to the spatial and temporal heterogeneity of the distribution of planthoppers.During the process of southward migration of BPH,the influx of four rice areas was consistent with the interannual variation trend of rainfall.The rainfall before the peaks of maximum immigration greatly promoted the immigration of N lugens' populations in the rainfall area.The probability of the coincidence between the two was as high as 70%.Among them,the rainfall process of light rain or moderate rain was most conducive to the immigration of BPH.(3)According to the statistics of the 15 representative stations in the southern China rice area,the maximum migration peak in 2006-2016 was 60% due to the influence of high-altitude trough,typhoon and cold front.The main reason is that the southwest warm and humid airflow generated by these systems provides favorable dynamic and thermal conditions for the migration of BPH.The high-humidity environment and the towed downdraft caused by the rainfall under the influence of the above weather system have a favorable influence on the concentrated landing of the BPH,and then the migration peak appeared.(4)The WRF model was used to simulate the case of August 28-30,2013.The hourly rainfall and the wind field at the altitude of 850 hPa were analyzed.It was found that when the BPH arrived 12 hours before the peak,the rainfall area is the most widely distributed and the rainfall is also the largest,as the rainfall area gradually shrinks,the rainfall gradually decreases and the peak appears.And the southwesterly wind and the flat westerly airflow at 850 hPa are very conducive to the large-scale migration of BPH. |
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