Overwintering of Rice Waika Virus in Rice Stubbles

In the unplowed paddy field, where rice waika disease was prevalent in the previous year, 76 out of 18, 620 rice stubbles regenerated spring ratoons. Rice waika virus (RWV) was recovered from 35 of 48 ratoons tested by Nephotettix cincticeps and by electron microscopy of the partiallypurified samples. From these results, it indicated that RWV was overwintered in the diseased rice stubbles in the unplowed paddy fields. The more spring ratoons from rice stubbles were found in year of warmer winter at around Chikugo, Fukuoka.