抄録
The control threshold of Chilo suppressalis in terms of the pheromone trap catches was estimated in Okayama Prefecture. In both cases of infestation caused by the first and the second generation larvae, a significant linear relationship between the total number of moth catches by the pheromone traps and the proportion of subsequent injured stems of rice plants was obtained. In addition, significant correlations between the total number of moth catches by the pheromone traps and the egg-mass density, and between the egg-mass density and the proportion of injured stems were detected in both generations. Thus, it was possible that the rice plant damage could be estimated by the pheromone trap catches. The relationship between the pheromone trap catches up to the peak day and the proportion of injured stems was examined for each generation, resulting in also a significant linear relationship in each of the generations. From this relationship, the pheromone trap catches up to the peak day (i.e. a tentative control threshold) corresponding to a 5% yield loss of rice plants were estimated to be 56 and 144 for the overwintered and the first generation moths, respectively.
