Title: Prepupal parasitoid Mastrus ridibundus eavesdrop on pheromonal communication of cocoon-spinning Cydia pomonella larvae
Abstract: As shown in a recent study, cocoon-spinning larvae of the codling moth, Cydia pornoneNa L. (Lepidoptera: Olethreutidae) employ a pheromone that attracts or arrests pupation site seeking conspecific larvae. Such intraspecific communication signals are important cues for illicit receivers such as parasitoids to exploit. I tested the hypothesis that the specialist prepupal C. pornonella parasitoid Mastrus ridibundus Gravenhorst (Hymenoptera: Ichneumonidae) exploit the larval aggregation pheromone to locate host prepupae. In laboratory olfactometer experiments, female M. ridibundus were attracted to 3-day-old cocoons containing C. pornonella larvae or prepupae. Older cocoons containing C. pornonella pupae, or larvae and prepupae excised fi-om cocoons, were not attractive. In coupled gas chromatographic-electroantennographic detection (GC-EAD) analyses of bioactive Porapak Q extract of cocoon-derived airborne semiochemicals, ten compounds elicited responses fiom the antennae of female M. ridibundus. Comparative GC-mass spectrometry of authentic standards and cocoon-derived volatiles determined that compounds were 3-carene, myrcene, heptanal, octanal, nonanal, decanal, (E)-2octenal, (9-2-nonenal, sulcatone, and geranylacetone. A synthetic 1 1 -component blend consisting of these ten EAD-active compounds plus EAD-inactive (+)-limonene (the most abundant cocoon-derived volatile) was as effective as Porapak Q cocoon extract in attracting both female M. ridibundus and C. pornonella larvae seeking pupation sites. Only three components [myrcene, (E)-2-nonenal, (+)-limonene] could be deleted fiom the 1 1 -component blend without diminishing its attractiveness for M. ridibundus which underlines the complexity of information conveyance during host foraging. Mastrus ridibundus obviously eavesdrop on the pheromonal communication signals of C. pomonella larvae that reliably indicate host presence. Whether the larval aggregation pheromone is as complex as the semiochemical blend attracting M. ridibundus is currently under investigation.
Publication Year: 2004
Publication Date: 2004-01-01
Language: en
Type: dissertation
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