Pheromones of the fig weevil Aclees taiwanensis: evaluation of their attractiveness in the laboratory and in the open field Feromoni del punteruolo del fico, Aclees taiwanensis: valutazione della loro attrattività in laboratorio e in pieno campo

The fig weevil Aclees taiwanensis Kôno (Coleoptera: Curculionidae) is an invasive species of Asian origin, accidentally imported in Italy (Tuscany) in 2005 through the trade of ornamental plants and it is currently present in seven regions of Central-Northern Italy. The insect attacks many species of the genus Ficus including the common fig, Ficus carica. The damage to plants is caused both by adults, which feed on buds, leaves, and ripening fruits and by the xylophagous larvae that dig tunnels at the base of the trunk. The control strategies implemented so far, with synthetic chemicals or biological agents, have not given satisfactory results. However, in other species of xylophagous beetles, it has been shown that the capture of adults through aggregation or sex pheromone can be applied to monitoring and/or control. This work aimed to verify whether reconstituted mixtures of Volatile Organic Compounds (VOCs), emitted by adults of both sexes of A. taiwanensis, are involved in the recognition and attraction of conspecifics and if it is possible to use them to control the fig tree weevil. The compounds contained in the VOCs were sampled through solid-phase microextraction (SPME) from insects collected in late spring-early summer 2019 and identified by gas chromatography coupled to mass spectrometry. The identified VOCs, terpenes with limonene as the main compound, were used both in the laboratory and in preliminary field tests to evaluate their bioactivity. In the behavioral laboratory tests, in a two-way olfactometer, the reconstituted VOCs containing the main compounds were found to attract the opposite sex. Reconstituted VOCs of both sexes containing also minor components attracted only females. These latter mixtures were also tested between June and July 2020 in a fig orchard. The reconstituted VOCs applied on salivary rollers placed under a textile sleeve (Rhynchotrap) surrounding the base of the tree trunk, resulted more attractive than control.The results obtained, although preliminary, suggest an attractive effect of reconstituted VOCs and their possible application for monitoring or mass trapping. However, further investigations will be necessary to determine the most appropriate modality to release the reconstituted VOCs in the field, the different activity of enantiomers of the chiral compounds, and the differences in the profile of the VOCs of adults collected in different periods of the year.