The brown planthopper (BPH, Nilaparvata lugens) and the white-backed planthopper (WBPH, Sogatella furcifera) are important pests of rice that are widely distributed in Asia. In particular, the brown planthopper grows rapidly in paddy fields, and heavy infestations can cause the wilting and complete drying of rice plants. It has been known  that wintering is not possible in East Asia, including China and Japan, and that every year during the rainy season, the planthoppers migrate to Japan via China, starting from the north central part of Vietnam, which is a region where planthoppers occur normally. In recent years, the arrival of insecticide-resistant populations has made it difficult to control with insecticides that have been used in Japan.

According to the outbreak forecast information for brown planthopper released by the Ministry of Agriculture, Forestry and Fisheries (MAFF) this year, an outbreak alarm has been issued in 28 prefectures and an outbreak warning in 11 prefectures west of the Tokai region (as of Oct 6) [1]. Due to the low temperature and lack of sunshine in July, the damage caused by typhoons and brown planthoppers has led to the decline of cropping index in some areas (as of Sep 15) [2].

The outbreak of pests involves multiple factors such as weather conditions and pesticide application conditions. In particular, migratory pests such as planthoppers are not only affected by the outbreak conditions such as weather, pesticide spraying etc. in Japan but also the conditions in the origins of planthopper migration such as Vietnam and China. Since 2016, JIRCAS has been conducting research aimed at establishing a comprehensive control system for planthoppers in collaboration with the Plant Protection Research Institute in Vietnam. So far, we have clarified the current status and problems in insecticide use by farmers [3]. We are currently analyzing the occurrence of planthoppers in Vietnam's winter-spring crops (rice transplanting around February to harvesting around May), which will affect the arrival in Japan this year. However, based on information from the Plant Protection Research Institute, the density  was about the same as usual although there are some areas where planthoppers have become denser. JIRCAS will continue its research with the aim of finding suitable control measures against planthoppers at the origin of migration.

References

[1] https://www.maff.go.jp/j/syouan/syokubo/boujyo/attach/pdf/120104_yoho-1…

[2] https://www.maff.go.jp/j/tokei/kouhyou/sakumotu/sakkyou_kome/attach/pdf…

[3] https://www.jircas.go.jp/en/publication/research_results/2019_b07

Contributor: MATSUKAWA Mizuki (Crop, Livestock and Environment Division)