Long-term seasonal forecasting model for the trans-regional migration of brown planthopper in Eastern China

The brown planthopper (BPH), Nilaparvata lugens (Stål), is the most important rice pest in China and other East Asian countries. Identifying their source areas and predicting their population dynamics are crucial for managing migratory pests. Northern South China (NSC) is one of the key regions for northward BPH migration and a direct source of BPH in the key rice-growing area of the Lower Yangtze River Valley (LYRV). Hence, this study aimed to explore the environmental drivers affecting the population dynamics of BPH in NSC, and develop models for predicting the immigration levels in the LYRV. Initially, the BPH immigrants in NSC were identified to have mostly originated from northern and north-central Vietnam, Laos, and northeastern Thailand (15°-22° N) in May by using a trajectory analysis approach. The population model showed that immigration size of BPH in NSC in May can be predicted by the temperature observed in February over these source areas combined with the probability of BPH from south-central Vietnam (their principal overwintering region) immigrating to these source areas in March. Subsequently, the immigration size of BPH in NSC in May combined with the onset time of the South China Sea Summer Monsoon (a sign of rain belt movement and arrival of the flood season in China), can be used to predict the immigration level of BPH in the LYRV in July. These 2 prediction models could forecast nearly 2 months in advance, allowing time for effective control measures to be implemented.