Global warming may affect crop damage caused by insect pest, by changing the degree of synchronization between pest occurrence and the susceptible stage of crops. The epidemiological system of rice stripe virus disease (RSV disease) transmitted by the small brown planthopper, Laodelphax striatellus (Fallen), is greatly influenced by synchronization, because the susceptible stage for virus infection is within several weeks after transplanting. We calculated how the area potentially vulnerable to RSV disease will change under future global warming by using the results of the Global Climate Model (GCM) experiments reported by the Intergovernmental Panel on Climate Change. For simplicity, assuming that rice seedlings are transplanted from May to June, we made a map, in which the number of generations of the small brown planthopper on June 1 was plotted by calculating the effective cumulative temperature. The influence of solar radiation was also considered in this calculation. We judged that the area located near the boundary of generations is potentially vulnerable to disease prevalence, because planthoppers are in the adult stage there. Generation maps indicated that the Tohoku and Hokuriku districts, which are major districts of rice production in Japan, might be potentially vulnerable to disease infection under future global warming. (Copyright by the Japanese Society of Applied Entomology and Zoology)




Figure 1.   (Left panel) Estimated number of generations (N) of the small brown planthoppers on June 1 under the baseline climate before global warming (average of 1952-1982). (Right panel) Estimated number of generations (N) of the small brown planthoppers on June 1 in the 2060s under global warming, estimated by the GCM model, CCSR/NIES. N = 0 indicates the overwintering generation. The area around a generation boundary is liable to be infected by RSV disease, since adult planthoppers immigrate to paddy fields in such areas.