Enhanced mating competitiveness of Ceratitis capitata males following exposure to citrus compounds

Previous work has demonstrated that exposure of males of the Mediterranean fruit fly, Ceratitis capitata (Diptera: Tephritidae), to the scent of sweet orange increases their mating success relative to non-exposed males. Here, we demonstrate that exposure to the commercial essential oils of bitter orange, mandarin orange, lemon and grapefruit confer to males a significant mating advantage as well. Likewise, exposure to peel-wounded mandarin oranges and lemons, and to peel-wounded sweet oranges of the Merlin, Newhole and Naveline varieties, also conferred a significant mating advantage. Exposure to peel-wounded grapefruits and bitter oranges as well as to sweet oranges of the local Greek variety Xino Artas enhanced mating success, however, not significantly. These results suggest that the chemicals responsible for mating enhancement in C. capitata are present in several citrus fruit species and varieties. In an experiment involving different doses of commercial sweet orange peel oil, males exposed to medium doses of 12.5 or 25l achieved significantly higher numbers of matings with virgin females than control males. Lower doses did not increase mating success, whereas higher doses killed a number of males. In another experiment we tested the effect of the seven most abundant individual chemical compounds of citrus oil (some of them also existing in the pheromone of males) and detected compounds with some potential for further trials. In a final experiment we created a mixture of those compounds (geraniol, -pinene, limonene, -myrcene and linalool) and found that wild or sterile males exposed to it achieved over 70% of all matings when competing with non-exposed males. Since the mixture did not contain -copaene (an expensive compound that is often invoked as responsible for the phenomenon of mating enhancement) our data could lead in a more cost-effective and efficient implementation of sterile insect technique (SIT) programmes against C. capitata.