Sexual chemical ecology of the olive fruit fly, Bactrocera oleae – where from, where to?
Abstract: Bactrocera oleae (Rossi), commonly known as the olive fruit fly, is a carpophagous tephritid attacking fruits of a few Olea species, including Olea europaea L. Currently, it is considered the major pest of commercial olives worldwide. The management of olive fruit fly is mainly based on the use of chemical insecticides, posing serious threats to human health and the environment. Regards to biological control agents, several braconid parasitoids have been evaluated to manage B. oleae populations, with patchy results. Concerning the use of semiochemicals in Integrated Pest Management, control programs rely to the major component of the B. oleae female sex pheromone, while in both sexes the B. oleae sexual chemical ecology is driven by a higher number of compounds, largely unknown. Indeed, the olive fruit fly has a peculiar sexual chemical ecology, guided by a rather wide number of male- and female-borne olfactory cues, mostly produced in glands associated to the rectal ampulla. Herein, we review current knowledge available about the sexual chemical ecology of olive fruit fly, giving peculiar emphasis to the connections between basic chemoecology and pest control perspectives. Notably, despite several decades of research on B. oleae chemical ecology, only few sex pheromone components (mainly 1,7-dioxaspiro[5.5]undecane) have been investigated in-depth. Furthermore, it has been recently outlined that young B. oleae males also produce 1,7-dioxaspiro[5.5]undecane in the rectal glands. Later, when B. oleae males become sexually mature, they increase the production of the compound (Z)-9-tricosene, which selectively attracts females. It has been reported that B. oleae females produce a multi-component sex pheromone containing 1,7-dioxaspiro[5.5]undecane, methyl dodecanoate, alpha-pinene, nonanal, and several C6-C18 fatty acid esters. Two of the latter group (i. e., methyl hexadecanoate and ethyl decanoate) attracted males and females, respectively. This represents the first evidence of a female-borne compound attracting conspecific females in the Tephritidae family. Overall, further research efforts are still needed to fully elucidate the sexual chemical ecology of the olive fruit fly, to develop novel and eco-friendly monitoring as well as “lure and kill” tools.