Abstract
The population density of male Plutella xylostella was estimated from a mark-recapture experiment using sex pheromone traps in small-scale cruciferous vegetable fields. Population density was calculated by the YAMAMURA method. Among five summer and four autumn experiments, the release-recapture data from two autumn experiments were not adequate for mathematical methods of density estimation. The number of wild male moths recaptured per sex pheromone trap (u0') showed a significant positive correlation with the estimated wild population density per 100 m2 (U^^^'), the ratio of U^^^'/u0' being estimated to be about 16.
