An epidemic model of a rice virus transmitted by a migratory planthopper

Abstract

Recent outbreaks of viral diseases of rice in east Asia are caused by migratory planthoppers. Epidemic models of these viral diseases are required to predict the annual emergence of the viruses based on established forecasting systems of outbreaks of the planthoppers. Here, we develop an epidemic model for southern rice black-streaked dwarf virus (SRBSDV), which is transmitted by the white-backed planthopper, Sogatella furcifera, as the first epidemic model of viruses borne by migratory planthoppers. The epidemic model, consisting of a Leslie model for the population dynamics of S. furcifera and a transmission model for SRBSDV, predicted a high contribution of the density of viruliferous immigrant S. furcifera to SRBSDV emergence. Early immigration of S. furcifera into paddy fields after transplanting of rice also promoted the virus epidemic primarily because of the emergence of viruliferous old nymphs during the period during which rice plants are susceptible to the virus. The epidemic model developed could be expanded to other planthopper-borne viruses and is effective for understanding the ecological aspects of virus epidemics in the field and for assessing the risk of viral diseases transmitted by migratory vectors.