Study On Migration Of Rice Two Migration Pests And Population Dynamics Of Important Natural Enemies In Xiang-gui Corridor

Rice planthopper and rice leaf roller (Cnaphalocrocis medinalis), have frequently broken out inrecent years in Asia and cause serious damage to rice production. Xiang-gui Corridor is the majorpathway for the seasonal northward and return migration of rice two migration pests. Studies on theoccurrence and migratory behavior of rice two migration pests will be beneficial for the prediction andsuppression of these pests in China and beyond. Studies on population dynamics of important naturalenemies will provide key guidance for the biological control of rice migratory pests. This study aims toelucidate migratory behavior of rice migratory pests and population dynamics of natural enemies inXiang-gui corridor and improve the level of monitoring and forecasting on rice migratory pests andbenefit integrated management, and also to prevent losses in agriculture and reduce many socialproblems caused by chemical control. The rhythm of flapping light on migratory pests during the wholenight and related potential effect on the trajectory analysis were studied from catches by the searchlighttrap with automatic time-switches. The seasonal aerial migration of Nilaparvata lugens was observed bya millimetric scanning entomological radar. We integrated the catch data of Sogatella furcifera in lighttraps from Lingchuan, Xing’an and Quanzhou located in the Xiang-gui Corridor and used theatmosphere and trajectory analysis sfotware such as Grads, Hysplit and ArcGIS to study the migratorycharacters of S. furcifera in different places of Xiang-gui Corridor. In the last, we analysed the reasonsto cause breakout of C. medinalis. The results were as follows:1. During spring immigratory peak periods of2012and2013, the flapping light peak time of riceplanthopper and Cyrtorhinus lividipennis were different, appearing every time intervals with mainlyafter mid-night. The flapping light peak time of C. medinalis was mainly in03:00~05:00in2012and2013. During emmigratory peak periods, the flapping light peak time of insects was mainly in19:30~21:00and21:00~22:30. During local action time, the flapping light peak time of insects wasmainly before mid-night. When limiting the landing time to the flapping light peak time, the trajectorysimulation showed more precise results.2. The seasonal changes of ladybug, lacewing and rove beetle in searchlight trap and Jiaduo lighttrap were obvious. The average trap numbers of ladybug and lacewing trapped in searchlight trap weresimilar in2012and2013. The average numbers of rove beetle trapped in searchlight trap were differentsignificantly in2012and2013. The seasonal changes of ladybug in searchlight trap were consistent in2012and2013. The seasonal changes of lacewing and rove beetle in searchlight trap were different in2012and2013. The population dynamics of ladybug and rove beetle were the same in searchlight trapand Jiaduo light trap, with the variousness of lacewing. The population numbers of three naturalenemies in searchlight trap were significantly more than in Jiaduo light trap. Population numbers ofrove beetle in both light traps were significantly positively correlated, with low correlation of ladybugand no correlation of lacewing.3. The phenomena of accompanying migration by C. lividipennis with N. lugens was obvious. Theinitial migration period of C. lividipennis obtained by both light traps was after that of N. lugens, then population dynamics of both insects were consistent. The peak period of trapped was from the late Julyto late August and there were more females in C. lividipennis catches.The peak period of trapped wasfrom the late July to late August and there were more females in C. lividipennis catches. Populationnumbers of both insects were significantly positively correlated. N. lugens could be controlled by thepredator when the population ratio between C. lividipennis and N. lugens reached or more than1:1.1.4. The seasonal aerial migrations of N. lugens were observed with a millimetric scanningentomological radar. The common orientation was analysed first. N. lugens took off at dusk and dawn,and the number of take off at dawn was low. In summer, planthopper-size targets generally flew at400-1800m above ground level, although some insects reached2000m above ground level; in autumn,they flew lower, generally at300-1100m although some insects reached1700m above ground level.Multiply layer concentrations were seen every night. N. lugens flew in strong winds. Femalesoutnumbered males in the summer migrations, and the males were more numerous in autumn. Inautumn, emigrants with strong flight capacity would have reached overwintering areas.5. The immigratory peak periods of S. furcifera in Xiang-gui Corridor lasted from the end ofMay to the mid-June. The initial immigration period was first appeared in Lingchuan at south ofXiang-gui Corridor. Population size was significantly different in three places in2007, and wassimilar in2008. The population size of3rdgeneration determined the population size of the year. Thesource areas of S. furcifera were mainly in the southwest of Guangxi, the north of Vietnam and the northof Laos. The southwest airflow stream of high altitude with more frequently and strong caused more S.furcifera’s migration, and the widely source areas.6. C. medinalis started to immigrate into Xing’an from mid-April. The number of4thgenerationwas the most, sometimes3rdgeneration and6thgeneration. Population size was significantly different indifferent years. Rainfall will promote landing of C. medinalis. The high temperature and droughtclimate will prevent larva’s growth. Population size was low in autumn, sometimes6thand7thgeneration increased. The flight capability of female was stronger than male. A large number ofimmigrant moths during spring migratory period was the main reason to cause C. medinalis bigoccurrence.