Outbreak mechanism of second generation armyworms innortheastern China: A case study in 1978
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：outbreak of armyworm, northeasternChina, strong southwesterly, heavy rainfall
Abstract：[Objectives] In some years newly emerged moths of the 1st generation armyworm, Mythimna seperata (Walker), in northeastern China fail to emigrate successfully because of adverse weather conditions and consequently remain in their birthplace to form 2nd generation populations that inflict serious damage on summer crops. Better understanding of the outbreak mechanism of such summer populations is important to improve our ability to forecast and manage these outbreaks. [Methods] A case study of an armyworm outbreak inHeilongjiangProvincein 1978 was performed using trajectory analysis of NCAR/NCEP reanalysis data using the WRF system. [Results] (1) Southwesterly winds were predominant in northeasternChinaas a subtropical high in the western Pacific remained stable further north than usual in July. M. seperata emigrating during these periods moved northward rather than southward, thus moths could not return to their summer habitats in northern China; (2) The swarm of moths that settled in Heilongjiang Province were a mixture of the local population formed by unsuccessful emigrants and immigrants from Jilin and Liaoning Provinces, and these moths produced the outbreak in Heilongjiang Province in 1978; and (3) Frequently passing cyclones, strong convective weather patterns and heavy rainfall acted as key factors to suppress the emigration of local moths and force large scale immigration into Heilongjiang Province. [Conclusion] The armyworm outbreak inHeilongjiangProvincein 1978 was caused by the retarded local emigrants of the 1st generation armyworm as a result of adverse weather and the forced landing airborne moths transported northwardly by strong southwesterly winds and then concentrated and swept to the Sanjiang Plain by large scale heavy rainfall.