Abstract
An investigation on the feeding time of Sogatella furcifera was carried out to clarify its relationship to rice damage using the variety Akitakomachi in Akita Prefecture in 2000. Transplanting date was on May 15 and the rice crop reached heading stage on July 31. The insect pest was introduced into the plots on July 5, July 15, July 25, August 5, and August 15 as treatments for a period of 35 days. There was no introduction of the insect pest in the control plot. In July 5 and July 15 treatment plots, culm length and the number of spikelets per panicle had lower values as compared to the control plot. However, reduction in yield was minimal. On the other hand, in July 25, August 5, and August 15 treatment plots, the percentage of ripened grains and the weight of 1000 kernels was low and yield loss was evident. This suggests that compensation reaction of rice growth is difficult in the late stage of the crop. Economic injury level should be studied in relation to the growth stage of the rice plant.
