Seasonal migration dynamics of Argyrogramma agnata Staudinger in Sanya City, Hainan Province

Argyrogramma agnata Staudinger is an important migratory pest that infests cruciferous and leguminous crops. Clarifying its seasonal migration patterns and population source characteristics in Sanya, Hainan Province, is of great significance for ensuring the security of local grain and vegetable production.

From July 2022 to December 2025, we used high-altitude light traps in Sanya City to monitor the migratory dynamics of A. agnata, and applied ovarian dissection together with trajectory simulation to determine the source populations, migration routes, and potential origin regions.

Migration activity of A. agnata in Sanya occurred primarily from March to August, representing 87.5% of the annual trap catch. Males consistently outnumbered females throughout this period. The annual migration could be divided into two distinct phases: the spring phase (March-May) and the summer phase (June-August). The mean ovarian development stage, sexual maturation rate, mating frequency and mating rate of the spring population were significantly lower than those of the summer population, indicating that the spring migratory population was derived from local sources, while the summer population was dominated by immigrant populations from outside regions. Trajectory simulation analysis further demonstrated that the spring population mainly migrated from Sanya, Hainan, to northern Vietnam, whereas the summer immigrant populations primarily originated from Vietnam, Laos, Thailand, and other regions.

This study demonstrates that A. agnata in Sanya exhibits a seasonal migration pattern characterized by the alternation of local emigration in spring and immigration of overseas populations in summer. The findings provide a theoretical basis for the regional monitoring, early warning, and control of this pest.