越南中北部稻飞虱回迁种群的崩溃与重建及其预测意义

The rice planthoppers (RPH, Nilaparvata lugens & Sogatella furcifera) are the most serious pests of the Asian rice production. People have long been believing that the hoppers migrate regularly northward in spring and summer and southward in autumn, that perform a perfect loop between Indo-China Peninsula and the mainland of China. However, some gaps in the loop were noticed during a field survey in northern Vietnam in November of 2009. Rice is the only food for RPH, but there was no rice planting in mid and north Vietnam during a 3-months interval between the two cropping seasons (summer-autumn rice and winter-spring rice). The broken food chain makes the returned hopper populations collapse completely, but then the hoppers from mid-south Vietnam (Quang Nam, Quang Ngai, Binh Dinh and Phu Yen, four provinces, from 13oN to 15.5oN), where there are year-round rice cropping, recolonize the winter-spring rice in mid-north Vietnam during next March. It is means that the hopper population dynamics in mid-south Vietnam will affect the formation process of source hopper populations and thus determine the damage extent of that year in China, so that makes a possible early warning index for the RPH immigration periods, quantities and spatial distribution in the spring invasion into southern China, So, we will reveal the biological and environmental factors that influence the formation process and dynamic machanisms of source hopper populations by spatio-temporal analysis with GIS and trajectory analysis on WRF through metapopulation approach and landscape ecology approach respectively, based on our six-year field survay data in Vietnam since 2008, the light-trap catch data provided by Vietnamese collaborators, and rice planting and developmental data extracted from satellite images, thereby obtain an operable early warning index for the RPH outbreaks in China.

稻飞虱（褐飞虱和白背飞虱）是我国水稻生产中的头号大害虫，其虫源主要来自越南中北部。长期以来人们一直认为，稻飞虱每年春季迁入我国秋季再迁回越南，构成一个完整的循环。但在与越南植保部门合作稻飞虱监测与防控研究过程中我们意外发现，由于越南中北部两茬稻之间长达三个月的间隔期造成食物链断裂而使稻飞虱回迁种群全军覆没，但在翌年三月又由越南中南四省稻飞虱虫源的补充而得以重建。这意味着，越南中南四省稻飞虱的发生动态将直接影响我国稻飞虱虫源的形成过程从而决定当年我国稻飞虱的发生程度，因此可能成为我国稻飞虱迁入期、迁入量和主降区的早期预警指标。为此，我们拟根据2008年以来的实地调查数据和越方提供的虫情资料，结合卫星遥感提取水稻种植和发育状况，分别从异质种群和景观生态的不同视角，通过GIS时空分析和WRF平台上的三维轨迹分析，揭示我国稻飞虱虫源的形成过程和机制及其影响因子，提取我国稻飞虱大发生的早期预警指标。

通过数值模拟和轨迹分析普查越南南方（中南六省、西原高原、东南部、湄公河三角洲）、老挝南部和中部、泰国东北部和东部、柬埔寨洞里萨湖周边诸省的虫源分布及2005-2014年10年的风温场，并分析我国稻飞虱种群发生的年际动态，明确了泰国东北部、老挝南部和中部、越南中南部可为越南中北部春季稻飞虱种群重建提供有效虫源，种群重建区的北界即16.5ºC等温线所在位置。明确了越南13ºN以南、柬埔寨和泰国东部没有合适的风场，从而无法建立有效的空中廊道为重建区输送虫源。而三月份冷气团低温南下的程度决定了年际间重建虫源能够顺利进入重建区的北界所在，也直接影响能够直接迁入华南的虫源数量。因灌溉条件和冬季休耕决定的旱季水稻田的点片分布形成的大陆尺度的迈他种群构成了越南中北部春季稻飞虱种群重建的虫源，也使得稻飞虱的重建过程从3月延续到7月、次第北上贯穿种植期随地理纬度增加而渐次北推的整个东亚水稻种植区。从3月份越南中北部的种群重建，到4月份越南红河三角洲的种群重建形成5月份入侵我国的主迁入种群，完成我国华南稻区飞虱种群的重建；此后则从华南到江南、从江南到长江下游直到韩国和日本，稻飞虱种群逐代北迁完成整个东亚种群的重建。因此，空中廊道的连通性决定了不同区域飞虱种群重建的成功与否，从而影响了各地稻飞虱种群的数量动态。可见，空中廊道连通性的年际变化可作为稻飞虱发生预测的早期预警指标。以广西全区三月上旬灯下稻飞虱累计虫量和三月份越南中南三省稻飞虱虫源直入华南的概率作为我国稻飞虱发生的早期预警指标，经对2007年以来及1998年以来历年发生情况的比对，该项预警指标有比较可靠的预警功能，比较成功地解释了稻飞虱发生程度的年际变化。根据以上研究成果发表SCI论文5篇，中文学报论文2篇，在《应用昆虫学报》出“中国稻飞虱的境外虫源”专刊一期，完全达到预期目标，超额完成研究任务。