Don't like your neighbours? Move!: Evidence of reduced natural enemy assemblages for mountain pine beetle that colonize spruce vs. pine

The ongoing mountain pine beetle (Dendroctonus ponderosae Hopkins) (Coleoptera: Scolytidae) epidemic in British Columbia, Canada now extends over approximately 13 million hectares of lodgepole pine (Pinus contorta var. latifolia) forest. Within the central interior of British Columbia, mountain pine beetle are attacking interior hybrid spruce (Picea glauca x engelmannii) with increasing frequency, in some cases leading to successful colonization and reproduction. Natural enemies (i.e., predators and competitors) may exert significant detrimental impacts on bark beetle reproduction at both adult and larval life stages. Although mountain pine beetle is recognized as an aggressive bark beetle during outbreak stages, it is typically thought to be a poor competitor with secondary colonizers such as Ips spp (Coleoptera: Scolytidae). While much effort has been undertaken to understand interactions between mountain pine beetle and its associated natural enemy assemblages in Pinus hosts, little is known about these relationships during occasions when mountain pine beetle colonize “unusual” hosts, such as Picea spp. This study examines the attraction and reproduction of natural enemies of mountain pine beetle in interior hybrid spruce vs. lodgepole pine hosts in the presence and absence of female colonizing beetles.