The common cutworm, Spodoptera litura (F.), feeds on a wide variety of food and cash crops and is one of the most widespread and destructive agricultural pests worldwide. Migration is the biological basis of its regional population outbreaks but the seasonal movement of this pest between east and south Asia regions remains unknown. In this study, searchlight traps were used to monitor the seasonal migration of S. litura from 2019 to 2023 in Ruili City (Yunnan, China), located along the insect migratory route between China and the south Asia region. The results showed that migratory activity could occur throughout the year, with the main periods found in spring (April–May) and autumn (October–December). The ovarian development and mating status of the trapped females indicated that most individuals were in the middle or late stages of migration and that Ruili City was located in the transit area of the long-distance migration of the pest. In the migration trajectory simulation, populations of S. litura moved from northeast India, Bangladesh, and northern Myanmar to southwestern China along the southern margin of the Himalayas in spring and returned to the south Asia region in autumn. Our findings clarify the seasonal migration patterns of S. litura in China and South Asia and facilitate the development of regional cross-border monitoring and management systems for this pest.

The oriental armyworm Mythimna separata (Walker) is a worldwide migratory pest that threatens food security in China. Previous studies have clarified the general migration regularity of M. separata in East Asia, but knowledge of migration routes over northeast China, especially in autumn as well as the impact by climate change in recent years, is still limited. From 2017 to 2020, we monitored the migration of M. separata in northeast China by searchlight traps and simulated moth trajectories by the HYSPLIT model. The M. separata moths had three main migration periods in northeast China, and there were obvious seasonal differences at different latitudes. The spring and summer migrants (late May to early-mid June and late July to early August) came from the southern Shandong Province and migrated to the north via Hebei/Shandong-Liaoning-Jilin-Heilongjiang. Moreover, more than half of the autumn trapped insects from late August to mid-late September migrated in the provinces where the sites are located, southward via Heilongjiang-Jilin-Liaoning. These results clarified the migration route of M. separata in northeast China and their relationship with the insect source in north China, thereby providing a theoretical basis for regional monitoring, early warning, and management of the pest.

Helicoverpa armigera (Hübner) is a destructive agricultural pest. Facultative migration usually causes regional catastrophes; therefore, developing a simple and easy new technology for the monitoring and early warning of immigrant populations is urgent. Between 2021 and 2023, we conducted a population-monitoring study on H. armigera immigrants in Xundian County, Yunnan Province, where the migration pathway for pests from southeast Asia extends to southwest China. Based on the differences in the reproductive organ development parameters of H. armigera at different ages, we established an adult age discrimination model. The monitoring results of field populations with semiochemical attractants and sex pheromones between 2021 and 2023 showed that the daily average age of the adult population of H. armigera fluctuated above 6 days, and the trapping dynamics with semiochemical attractants and sex pheromones were the same. Both trapping methods yielded H. armigera males of different ages and had identical age structures, indicating that the H. armigera population primarily migrated from other regions. The trajectory analysis showed that the H. armigera population that migrated to Xundian between May and September was primarily from South Kunming, and after October, it was primarily the southward-migrating population north of Qujing City, Yunnan Province. Based on the relationship between the daily average fecundity and the age of H. armigera, a dynamic prediction model for the fecundity of the immigrant population was established. In this study, the prediction models and methods based on semiochemical attractants could potentially be used in the surveillance and population alerting of H. armigera.