Outbreak mechanism of second generation armyworms in northeastern China: A case study in 1980

Author of the article:HU Gao1 WU Qiu-Lin1 WU Xiang-Wen1# JIANG Yu-Ying2 ZENG Juan2 ZHAI Bao-Ping1**

Author's Workplace：1. Key Laboratory of Integrated Management of Crop Diseases and Insect Pests (Ministry of Education and Ministry of Agriculture,Department of Entomology, Nanjing Agricultural University, Nanjing 210095, China;2. Division of Pest Forecasting, National Agro-Tec Extension and Service Centre, Beijing 100125, China

Key Words：Mythimna separata, WRF model, trajectory analysis, northeast cyclone

Abstract： [Objectives]  An outbreak of 1st generation armyworm, Mythimna separata (Walker) occurred inHeilongjiangProvincein 1980, and numerous newly emerged moths were caught by poplar branch traps. However, an outbreak of 2nd generation armyworm subsequently occurred inJilinProvincerather than inHeilongjiangProvince. Where did these moths emigrate to and what was the source population? This study aims to provide suggestions for forecasting and controlling M. separata by investigating the migration process and the formation of outbreak populations. [Methods]  The outbreak inJilinProvincein 1980 was studied by calculating trajectories using WRF, a mesoscale numerical weather prediction model. [Results]  In 1980, the emigration of moths fromJilinProvincewas suppressed by successive rainfall caused by passing cyclones, which also flushed out the passing southward airborne migrants fromHeilongjiangProvince. Thus, the outbreak population inJilinProvincein 1980 was comprised of both the local population and immigrants. In addition, as the west Pacific subtropical high remained farther south than usual and the Yakutsk high reached the central plain of northeastern China in the sixth pentad of July, a few of moths from Liaoning Province could immigrate into Shandong and Hebei across the Bohai Sea with the prevailing northerly winds. [Conclusion]  The primary cause of the outbreak of 2nd generation M. separata inJilinProvincein 1980 was the prevention of emigration of local populations and the concentrated immigration of both southward and northward airborne moths by fickle winds and heavy rainfall in the season.