Automated tephritid fruit fly semiochemical mass feeding structure: design, construction and testing

Research has shown that exposure to semiochemicals significantly improves the mating performance of males from some of the most economically important agricultural tephritid fruit fly pests species. There is consequently a growing awareness of the need to include a pre-release semiochemical treatment in sterile insect technique pest control programmes, to ensure optimal sexual performance of sterile male flies vis-a-vis wild males and to ensure their survival in the wild. This is, however, not a matter of simply spraying flies with the semiochemical as several species (including Bactrocera dorsalis and Bactrocera carambolae) need to actively ingest and metabolize the chemical for it to have the desired effect. Currently, no economical or efficient method exists for large-scale administering/feeding of semiochemicals to such species. This may be due to the complicated requirements of (i) administering the semiochemical only to flies that are close to sexual maturity, (ii) assuring fixed-dose feeding to avoid damaging over exposure to flies and (iii) segregating semiochemically satiated from non-satiated flies prior to release. Using an engineering approach, while leveraging biological behaviour patterns (such as attraction to the semiochemicals and light), a mass semiochemical feeding structure was designed that fulfils all three requirements. The aim of the design was furthermore to maximize survival of flies and to minimize semiochemical wastage and hence cost. To validate the proposed design and to ascertain the behaviour of insects interacting within such a structure, a prototype was constructed and tested for B.dorsalis (with methyl eugenol as the attractant) and Ceratitis capitata (with citrus oil as the attractant). Our results show that the used semiochemicals and drivers, especially the novel conveyor belt system, are effective in encouraging the flies through the facility with minimum damage and without backward motion of flies.