Mating Competitiveness of Irradiated Mexican Fruit Fly (Diptera: Tephritidae)

Laboratory and field case studies were conducted with two laboratory cultures (one ≈34 yr old and the other 2 yr old). Each culture was divided into irradiated and unirradiated groups and tested in competition against the feral Mexican fruit fly, Anastrepha ludens Loew. The feral fly was collected from its native host Sargentia gregii S. Wats. Unirradiated laboratory-reared flies were very competitive with feral flies. In caged full grown trees, sterile males from the old culture were one-third as successful and those from the 2-yr-old culture were one-fifth as successful in mating as the feral flies. Irradiation also slowed the mating response of laboratory-reared males as compared with unirradiated males, but the slow response put the flies in phase with the mating period of the feral flies. Of 865 captured pairs, 63% were on leaves. Of 241 captured pairs of flies that had mated within each group type, we recorded 77% of them in the peripheral half of the tree bisected by the NE cardinal point. Irradiated males from the old laboratory culture produced 65% as much pheromone as unirradiated males. Only 6% of irradiated females from the same culture responded to a male-produced pheromone extract as compared with unirradiated females.