Tracing the shifting spatio-temporal migration patterns of rice planthoppers and leafrollers across China

The 'two migratory' pests of rice (brown planthopper Nilaparvata lugens (Stål), white-backed planthopper Sogatella furcifera (Horváth), and rice leafroller Cnaphalocrocis medinalis (Guenée)) have long posed a serious threat to the safe production of rice in China. This study aims to clarify the occurrence dynamics and migration patterns of the 'two migratory' rice pests under new circumstances such as global climate change and changes in cropping systems.

Based on pest monitoring data since 2000, the spatio-temporal evolution characteristics of the migration pattern of rice 'two migratory' pests in China was systematically analyzed.

Nationwide, the cumulative population of planthoppers declined over the study period, with two distinct stages. The initial appearance period of brown planthoppers was delayed in the Yangtze River basin, but remained unchanged elsewhere. The peak period of white-backed planthopper advanced in the Nanling area, north of Nanling area and Yangtze River Valley, whereas no significant shifts were detected in other areas. During the initial northward progression, the mean latitude of the main gathering areas shifted significantly poleward. Zooming to regional scale, significant fluctuations were noticed against the overall declining trend: spring immigration into the Nanling and north of Nanling area showed no decline; instead, the peak period advanced. In contrast, the number of rice planthoppers in the Yangtze Huaihe River area declined on the whole, although the coefficient of variation rose sharply, indicating intensified annual fluctuations in local populations. In Sichuan (Southwest China), the population of white-backed planthopper increased during the spring and summer migration seasons. The field population of the rice leafroller generally showed a declining trend; the initial appearance period was delayed in the Yangtze Huaihe River area and Yunnan Province; the main gathering areas shifted northward in late spring, leading to earlier peak periods in the Nanling area.

The results of this study can provide theoretical support for the accurate prediction and effective control of rice migratory pests in the context of global warming.