Biological activity of metabolites extracted from Citrus spp. on Ceratitis capitata(Wiedemann) (Diptera: Tephritidae)


Abstract: The Mediterranean fruit fly (Medfly), Ceratitis capitata (Wiedemann) (Diptera:Tephritidae), is one of the most injurious pest at global level. During the last years, severalelectrophysiological and behavioural studies have been carried out in order to investigate plantvolatile compound-insect interactions with the aim to use this knowledge in sustainable controltechniques.It has been observed that lemons are not attacked by medfly, probably because of the peeloil, that is toxic to other fruit flies. In the present paper electrophysiological recordings wereconducted to evaluate the insect sensitivity to peel extract and peel oil of two Sicilian cultivars(Interdonato and Lunario) of Citrus x limon (L.) Burm.f. on C. capitata females. Behaviouralbioassays were also performed to show their possible biological activity (repellent, antioviposition,insecticidal). C. limon peel extracts in different solvents (petroleum ether, dichloromethaneand methanol) were investigated at various concentrations using a single cell recordingtechnique (stimulation of tarsal taste chemosensilla). Different tarsal taste cell responses to thetwo cultivars were recorded. The higher sensitivity was evoked by C. limon Interdonato,particularly to the methanol extract, which elicited significant increases in the spike frequency atincreasing concentrations. The peel oil of the same cultivars as well as that ones of other two C.limon varieties (Monachello and Femminello) have been tested by EAG techniques. The EAGdata showed a high sensitivity (about -8.0/8.5mV) of the medfly antennae to the oils of Citrusspp. and a clear dose-response relationship. Responses of adult females (virgin and mated) toCitrus spp. peel extract were quantified in a double-choice test using yellow spheres (diameter7.0cm) housed in field cages. Preliminary tests conducted on three extracts of C. limonInterdonato and Lunario have provided interesting results. It was recorded a general decrease ofthe oviposition on treated spheres compared to control and in the case of the cultivar Lunario, amortality of insects.

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