Dispersal of released male sweetpotato weevil, cylas formicarius (Coleoptera: Brentidae) in different seasons

Dispersal of reared adult male sweetpotato weevils, Cylas formicarius (F.), was examined in different seasons using a mark-release-capture method in Okinawa, Japan, where a sterile insect release project has been conducted to eradicate the weevil. Release and capture were replicated 7 times in different seasons in the same locality consisting mainly of sweet potato and sugarcane fields. About 8,000 males were marked each time, thus 54,444 males in total were released, and 14,746 of them were captured by pheromone traps (27.1%). Population parameters, including dispersal, capture and survival rates of released males, and population density of wild adult males were estimated. Percentage captured and dispersal distance were positively correlated with mean temperature during each experiment. The highest estimated population density of wild males was found in the summer. The results offer strategical parameters for a successful eradication project against the weevil using the sterile insect technique.