Improving male mating competitiveness and survival in the field for medfly, Ceratitis capitata (Diptera: Tephritidae) SIT programs.

The success of the sterile insect technique (SIT) depends critically upon mating between released sterilized males and wild females. In Hawaii, improvements in the efficiency of sterile males were attempted on two separate fronts--mating enhancement and survival improvement. In the former, two methods have been investigated--selective breeding and aromatherapy. In the latter, flies which survived in field cages for several days were selected and bred to produce progeny with enhanced survival ability compared to control flies. Regarding mating selection, standard laboratory-reared males that successfully mated with wild females in field cages were allowed to breed. F1 offspring were inbred, then the selection procedure was repeated for four additional cycles. In the aromatherapy procedure, laboratory-reared males were exposed to ginger root oil for several hours 1 day prior to testing in field cages. Compared to controls, the selected flies improved the mating competitiveness of male flies ca. 3-fold, irradiation reduced this increase to ca. 2.5-fold. Exposing the selected, hybrid strain raised the fitness of the lab males to ca. 9-fold that of wild males. In the ongoing survival selection study, we have obtained lines in which the selected males survived ca. 2-fold better than laboratory control males over several days in an outdoor field cage, with food and water provided. The goal is to combine the traits of higher survival and mating ability into a single strain for SIT release.