Hybridization and use of grapes as an oviposition substrate improves the adaptation of olive fly bactrocera oleae (Rossi) (Diptera: Tephritidae) to artificial rearing conditions

The olive fly Bactrocera oleae (Rossi) is the key pest for olive cultivation worldwide. Substantial effort has been invested in the development of the sterile insect technique (SIT) to control this pest. One of the limitations to develop SIT technology for olive fruit fly is the low ability of wild females to lay eggs in other medium than olive fruits, and their slow adaptation to oviposition in artificial substrates. In the present study, fruit grapes were used as an alternative egg collection medium to harvest eggs and young larvae from freshly colonized wild strains originating from France, Italy, Spain and Croatia. The larvae were allowed to develop into the fruits until the second instar, before they were extracted out and further reared on a standard artificial diet. Furthermore, F1 to F4 female flies were alternatively offered wax bottles to oviposit. Finally, the performance of hybrid strains created from crosses between wild and long colonised flies was assessed. The results showed that females of all 4 wild strains readily oviposited eggs in grapes and from the F2 generation onward, females from all strains were adapted to laying eggs in wax bottles. No difference was observed in eggs and pupae production among all strains tested. The findings are discussed for their implications on SIT application against olive fruit fly.