Analysis on the migration of first-generation Mythimna separata(Walker) in China in 2013

Mythimna separata（Walker） is an important pest which can cause serious damages to cereal crops. In the past two decades, several heavy outbreaks have taken place in northern China. In order to develop a fine-scale method of forecasting outbreaks, population data were collected in northern China using searchlight traps and ground light traps. A background weather pattern analysis and trajectory analysis were performed via the Weather Research and Forecast（WRF） and FLEXPART models. Our results showed that heavy migration of first-generation M. separata appeared in northern China in 2013. In Yanqing District, Beijing, the cumulative number of captured adults in searchlight traps was around 250000 and the daily maximum for trapped moths was 86000. During the peak period, the majority of M. separata moths arrived after 00：00 every night. The sex ratio（female：male） at each monitoring site was greater than 1 and greatly fluctuated with population dynamics. During the migration peak, prevailing downdraft winds benefited M. separata moths to land passively. Trajectory simulation showed that immigrants were from Anhui, Jiangsu and Hubei provinces and most of them could continue to fly into the northeastern regions of China. These results provide technical support for fine-scale forecasting of the outbreak of M. separata at meso-and micro-scale.

Trajectory modeling revealed a southwest-northeast migration corridor for fall armyworm Spodoptera frugiperda(Lepidoptera:Noctuidae)emerging from the North China Plain

The fall armyworm Spodoptera frugiperda,an invasive insect pest native to the Americas,has established populations throughout eastern China.The North China Plain一a key corn-producing area in East China with a unique topography一was invaded by fall armyworm in 2019 and is seriously threatened by this migratory pest.However,the spatiotemporal extent of the migratory movements of fall armyworm from the North China Plain remains poorly understood.Using an air transport-based trajectory modeling approach that incorporates flight behavior,we simulated the potential nocturnal migration trajectories of fall armyworm from the North China Plain based on historical meteorological data from June to October of 2015-2019,and examined the night-time atmospheric conditions associated with their possible flights.The emigration patterns showed monthly variation in the main landing area and common migration direction.The displacement of newly emerged moths from the North China Plain was concentrated in the Northeast China Plain(including Liaoning,Jilin and Heilongjiang provinces)before late summer,after which they were most likely to undertake return flights to the south(especially into Hubei,Anhui and Hunan provinces).This southwest-northeast aerial migration corridor follows the topography of East China and is affected by the East Asian monsoon.These topographic-atmospheric conditions have resulted in the North China Plain becoming a key stopover for fall armyworm populations engaging in multigenerational long-distance migration across East China.These findings contribute to our knowledge of fall army-worm migration and will aid in the implementation of management and control strategies against this highly migratory agricultural pest.