Investigating the effects of symbiotic fungi on the flight behaviour of Sirex noctilio (Hymenoptera: Siricidae)

AbstractThe invasive woodwaspSirex noctilioFabricius (Hymenoptera: Siricidae) is obligately associated with the symbiotic white rot fungusAmylostereum areolatum(Chaillet ex Fries) Boidin (Basidiomycota: Amylosteraceae), and shows positive chemotaxis to volatiles emitted by this symbiont. After introduction to North America,S. noctiliowas collected carrying another fungus speciesAmylostereum chailletii(Persoon) Boidin, used symbiotically by native North AmericanSirexLinnaeus. We conducted flight behaviour studies in a walk-in flight tunnel to evaluate specificity of the attraction of mated and unmatedS. noctilioto its primary symbiont,A. areolatum, versus the alternative symbiont,A. chailletii. Fewer unmated than matedS. noctiliofemales responded to either of the fungi. Unmated females showed no landing preference but matedS. noctiliofemales were attracted toA. areolatumalthough avoidance ofA. chailletiiwas not complete. Chemical analysis demonstrated major differences in the volatile profiles of the two fungal species. Sesquiterpenes dominated theA. areolatumsamples, whereas only two aromatic volatiles were consistently present in the nativeA. chailletii.