Swarms of brown planthopper migrate into the lower Yangtze River Valley under strong western Pacific subtropical highs

Windborne migration of insects is significantly influenced by meteorological factors and phenomena, such as seasonal atmospheric circulation. Large-scale movement of air provides the background for all weather and climate events. Hence, population abundances of migratory insects may fluctuate due to variations in seasonal atmospheric circulation, but little is known about this process. The western Pacific subtropical high pressure (WPSH) is the major circulation system that affects weather and climate in eastern Asia. Annual migration of the brown planthopper (BPH, Nilaparvata lugens [Stal]) in East Asia and the WPSH was investigated. Based on almost three decades of data (1977-2003), it was determined that swarms of BPH migrate into the lower Yangtze Valley in July and form an outbreak population under strong WPSH conditions. An intense WPSH enhanced southwesterly airstreams in southern China to provide a high-speed vehicle promoting BPH long-distance migration. In addition, increased precipitation in the Yangtze and Huai valleys formed a rain-belt barrier that forced BPH landing in the lower Yangtze Valley. Results herein demonstrate that the population abundance of a migratory insect fluctuated in response to climatic conditions caused by seasonal atmospheric circulations.