Evidence of interaction between Sirex noctilio and other species inhabiting the bole of Pinus

* 1Sirex noctilio is a woodwasp native to Eurasia and Northern Africa and has recently been found infesting pines in eastern North America. Its pest status in this new range is not yet known, although it is an important pest in other areas where it has been introduced. Pinus spp. in North America are hosts to several native and alien species of subcortical insects. Interactions between the woodwasp and these species may influence its distribution or the characteristics of its life history, thus affecting its population dynamics over time. * 2Sixty S. noctilio-infested Pinus spp. were felled in Ontario, Canada, and all phloem-feeding and woodboring insects were collected and identified from each 1-m section of the tree. * 3Sirex noctilio was in a tree alone 10% of the time but commonly shared the tree with subcortical beetles, such as Tomicus piniperda, Pissodes nemorensis, Ips grandicollis, Gnathotrichus materiarius and Monochamus carolinensis. The woodwasp was distributed throughout the tree stem and this distribution overlapped with that of the beetles. * 4Fewer but larger S. noctilio males emerged from trees with beetles compared with those without, although there was no statistical difference in females. * 5These findings suggest that co-habiting beetles could negatively affect S. noctilio population dynamics over time. The potential mechanisms for this interaction are discussed.