Behavioural and electrophysiological responses of Pantomorus cervinus (Boheman) (Coleoptera: Curculionidae) to host plant volatiles

Fuller's rose weevil (FRW; Pantomorus cervinus) (Coleoptera: Curculionidae), a polyphagous pest of citrus and other horticultural plants, was studied in laboratory assays designed to identify potential semiochemicals from host plants that might be exploited for weevil pest management. Using still-air bioassays, weevils were found to be most attracted to fresh whole lemon leaves compared with cut and/or dried lemon leaves. White clover, an understorey plant in kiwifruit orchards, was also found to be attractive to weevils in the dual-choice tests. Coupled gas chromatography-electrophysiological recording of weevil antennal responses to commercial extracts of lemon leaves indicated that weevils detected at least eight monoterpene components of the oil, i.e. linalool, terpinen-4-ol, nerol, neral, geraniol, geranial, neryl acetate and geranyl acetate. Significant antennal dose-responses were evident to lemon leaf oil, lemon constituent odours and two major green leaf volatiles detected from clover (Z)-3-hexenol and (Z)-3-hexenyl acetate. Still-air dual-choice tests on individual chemicals showed significant repellency from seven of the lemon leaf compounds at 500 mu g/100 mu L (all except geranyl acetate). Weevils were attracted to a synthetic blend consisting of the green leaf volatiles over a range of concentrations (1, 10 and 100 mg/100 mu L), as well as to clover leaves. These plant kairomone components may be potentially useful as repellents or attractants for FRW control and management programme.