European woodwasp (Sirex noctilio) in Ontario pine forests: Examining mortality factors of a worldwide pest in a newly invaded environment

Sirex noctilio Fabricius (Hymenoptera: Siricidae) is a worldwide pest of pine.  Although not a pest in its native Eurasian range, S. noctilio has caused extensive damage to exotic pine monocultures in the Southern Hemisphere.  North America differs from many other areas where S. noctilio has been introduced in its heterogeneous forests composed mostly of native pines, and a rich community of subcortical insects, including other woodwasps and their natural enemies. It is not known how S. noctilio will interact with native subcortical insects in North American pine ecosystems.  We examined stage-specific mortality factors and their relative importance on S. noctilio populations, generating life tables drawn from experimentally manipulated and natural populations of S. noctilio in Ontario pine forests.  Host-related mortality, particularly during the egg/neonate stage, was likely most important in limiting S. noctilio populations, in both experimental and natural populations.  Also, native parasitoids, particularly Ibalia spp., were common mortality factors, and have potential to limit S. noctilio populations in Ontario.