# Aerial Trajectories and Meteorological Drivers of Transboundary Loxostege sticticalis Migration Across Northern China and Mongolia, 2022

## TL;DR

This study maps the migration routes of beet webworms between China and Mongolia in 2022 and identifies weather patterns that influence their movement.

## Contribution

The study reveals transboundary migration routes and meteorological drivers of Loxostege sticticalis between China and Mongolia using 2022 data.

## Key findings

- Significant population exchanges occurred between China and Mongolia with primary southeastward migration from Mongolia.
- The Northeast China Cold Vortex and Mongolian Cyclones influenced migration patterns and landing areas in northern China.
- L. sticticalis populations from North China migrated into Northeast China and Mongolia after 1–5 nights of flight.

## Abstract

The beet webworm Loxostege sticticalis (Linnaeus) is a major migratory pest that frequently occurs in the temperate regions of northern China. To understand the source area–destination relationships and the meteorological mechanisms between northern China and Mongolia Loxostege sticticalis (Linnaeus) populations during the peak period, this study examined the migration pathways of this pest in 2022 using light trap data from northern China and field surveys in Mongolia. Results show significant population exchanges between two countries, with a primary southeastward migration route from Mongolia, along with eastward and southwestward routes. Major landing areas were identified in Northern and Northeast China. Populations from North China can migrate into Northeast China and Mongolia after 1–5 successive nights of flight. The Northeast China Cold Vortex (NCCV) and Mongolian Cyclones remarkably influence the synoptic patterns that govern migration, with their spatiotemporal characteristics critical to determining transboundary routes and distances of L. sticticalis migrants.

Clarifying migration pathways and the source area–destination relationships of the domestic and foreign beet webworm Loxostege sticticalis (Linnaeus) populations, as well as understanding the meteorological mechanisms shaping these processes, is pivotal for remote, accurate, and location-specific pest early warning and forecasting. Based on light trap data from northern China and field survey data from Mongolia in 2022, we simulated the migration trajectories, source regions, and primary landing areas of L. sticticalis by using the HYSPLIT model and analyzed the synoptic systems, processes and conditions during its migration. The results indicate the frequent exchange of L. sticticalis populations between China and Mongolia in 2022. The L. sticticalis migrants initiating their flights from Mongolia primarily undertook a southeastward migration pathway, supplemented by eastward ‘cyclonic’ and southwestward paths. The main landing areas were located in North China and Northeast China, with migration events potentially extending to the Shandong, Heilongjiang, and Xinjiang provinces. Populations originating from North China exhibited a capacity for migrating into Northeast China and Mongolia through 1–5 consecutive nights of flight. During this period, the Northeast China Cold Vortex (NCCV) and the Mongolian Cyclone alternately regulated the synoptic circulation pattern governing the migration of L. sticticalis. The spatiotemporal distributions and intensities of these systems were key determinants of the transboundary migration routes and distances of L. sticticalis. The NCCV dominated, and the precipitation and downdrafts it induced were crucial for the massive landing of L. sticticalis in northern China.