Spread and yield loss mechanisms of rice stripe disease in rice paddies

Rice stripe disease is an economically important disease of rice caused by the Rice stripe virus (RSV), which is transferred by the small brown planthopper (SBPH). The recent rapid increase in damage to rice crops throughout Japan caused by this disease makes it imperative to develop control methods as soon as possible. To obtain basic data for developing such methods, we studied how the disease causes damage and spreads within paddy fields. Our investigations revealed that diseased plants first appear in mid-June to early July, after which the disease spreads from affected plants to adjacent plants. This suggests that SBPH carrying RSV enter paddy fields, where they infect plants as they move about and lay eggs. Subsequently, hatched viruliferous nymphs infect surrounding plants, thereby spreading the disease. Our analysis of the damage caused by rice stripe disease showed that the earlier the onset of disease, the more extensive the damage caused, and that the disease reduces yield by reducing the number of healthy panicles. This suggests that to reduce damage caused by this disease, it is necessary to ensure the growth of a sufficient number of healthy panicles by controlling the vector insect during the crop's early growth period. To be most effective, pest control efforts should be timed to target either the first-generation adults that colonize the paddy fields or the second-generation nymphs and adults that cause the rapid increase in the number of diseased plants within a field.