Occurrence of rice bugs causing pecky rice in paddy fields that restored after the tsunami after the Great East Japan Earthquake

To investigate the occurrence of rice stink bugs causing pecky rice and weeds in paddy fields that were devastated by the tsunami caused by the Great East Japan Earthquake, we examined rice stink bugs, pecky rice, weeds in restored paddy fields and land-use types around paddy fields in Natori City, Miyagi Prefecture from 2014 to 2016. The occurrence of weeds in paddy fields in the inland area (damage was less serious and took a short time to recover) did not change significantly compared with that before the tsunami. However, in the coastal area (damage was serious and took a long time to recover), the percentage of paddy fields where Echinochloa sp. and Bolboschoenus maritimus occurred was higher than that in the inland area. Furthermore, the occurrence of rice stink bugs differed between the inland area and the coastal area. In the inland area, the pecky rice damage in rice fields with Schoenoplectus juncoides (Roxb.) Palla was more severe than that in fields without S. juncoides. However, in the coastal area, there was no difference in damage between fields with and without S. juncoides. Moreover, the population of rice stink bugs was high in paddy fields in coastal area. We suspected that rice stink bugs came from the area around paddy fields. We also confirmed that rice stink bugs were abundant in fallow areas with Echinochloa sp. and B. maritimus. We examined the relationships among the land-use types within a 300 m radius around paddy fields, the abundance of pecky rice bugs, and severity of pecky rice damage. As a result, the probability of pecky rice damage was found to be positively correlated with the area of land covered with Gramineae and Cyperaceae plants within a 300 m radius around each paddy field. Therefore, to minimize the severity of pecky rice damage in restored paddy fields, it is important to reduce the area of land covered with Gramineae and Cyperaceae plants around paddy fields and remove S. juncoides in paddy fields.