Rice stripe virus (RSV), which causes chlorotic stripes, mottling, and necrotic streaks on rice (Oryza sativa L.), is one of the major causes for yield losses at some places in Kanto area, Japan. Controlling small brown plant hopper (SBPH, Laodelphax striatellus), a vector of RSV, using chemical insecticides is crucial to decrease RSV infection in such regions. To optimize the timing of spraying the insecticides in paddy fields for distinct regions, the emergence date was predicted by the effective cumulative temperature method using temperature data obtained from the Agro-meteorological Grid Square Data System. The predicted dates of the second instar nymph of SBPH in five distinct locations (one each in Mito and Tsukuba, and three in Chikusei) in Ibaraki Prefecture were June 8, May 31, June 5, June 10 and June 1, which were less than 2 days apart from the emergence date determined by surveys in the actual fields. Therefore, this prediction would be effective to reduce the damage caused by RSV.
