Interannual and seasonal migratory patterns of wheat aphids across the Bohai Strait in eastern Asia

The bird cherry-oat aphid (Rhopalosiphum padi) and the grain aphid (Sitobion miscanthi) are two destructive wheat pests that have caused severe economic losses in China's main wheat-producing regions. Although previous studies have focused mainly on the population dynamics of wheat pests in wheat fields, little is known about the trans-sea migration of both wheat aphid species in eastern China. Here, we conducted 10 years of monitoring from 2012 to 2021 to determine aerial migration patterns utilizing a suction trap on Beihuang Island (BH), a small island in the centre of the Bohai Strait that serves as a seasonal insect migratory pathway in eastern Asia. We also simulated the migration trajectories of these pests using the HYSPLIT model. Overall, a total of 6362 alatae S. miscanthi and 335 alatae R. padi were captured, and both wheat aphid species exhibited regular patterns of comigration across the sea from late April to late October each year. There were significant interannual and seasonal differences in the migratory numbers of both wheat aphids. Notably, the average daily humidity was the most important meteorological factor affecting migration biomass. The seasonal migration trajectories simulated using the HYSPLIT model revealed different source areas for both wheat aphid species, which mostly originated in Northeast, North and East China. Accordingly, our study provides valuable insights into the occurrence and migration route of wheat aphids in eastern Asia, helps fine-tune forecasting and early warning systems, and thereby guides integrated pest management of wheat aphids in eastern Asia.