MASS TRAPPING OF THE SWEET-POTATO WEEVIL CYLAS-FORMICARIUS (FABRICIUS) (COLEOPTERA, BRENTIDAE) WITH A SYNTHETIC SEX-PHEROMONE

The suppressing effect of mass trapping with a synthetic pheromone on the population of the sweet potato weevil, Cylas formicarius, was studied in a small sweet potato field in Okinawa, Japan. The traps captured 65,214 males and 18 females from July, 1989 to December, 1990. In the pheromone-treated field, the sex ratio of the population largely skewed to female and the mating rate of females was reduced. The density of weevils was notably decreased in the pheromone-treated field, probably due to male annihilation and mating disturbance. Thus, mass-trapping is promising as a controlling agent against the sweet potato weevil.