Abstract
Three factors affecting the trap catch of the rice stem borer, Chilo suppressalis (WALKER) were examined. Synthetic sex pheromone which consists of (Z)-11-hexadecenal, (Z)-13-octadecenal and (Z)-9-hexadecenal (48 : 6 : 5 ; total 0.6 mg per rubber septum) was used as lure. Trap types (water-trap and sticky-trap), trap heights (0.5 m and 1 m above the ground) and trap locations (inside and at the boundary of paddy fields) were analysed and trap catches of males were counted over two flight seasons for two years in the southern part of Okayama Prefecture, western Honshu, Japan. In the first flight season, the trap catches were significantly greater at trap heights of 0.5 m than at 1.0 m, at field boundaries than in field centers and in water-traps than in sticky-traps, respectively. In contrast, the second flight season's trap catches were not significantly different between trap heights, locations and types. Peak times of trap catch in each season were not affected by these trapping variables. Seasonal patterns in trap catches inside paddy fields and at field boundaries were remarkably different. In the latter, numbers of males trapped in the first flight season were much greater than those in the former. Sticky traps set at 0.5 m above the ground of the boundary are adequate for population monitoring throughout the flight seasons.
