The suitability of novel hosts for Grosmannia clavigera and Ophiostoma montium, two common fungal associates of mountain pine beetle (Coleoptera:Curculionidae)

The mountain pine beetle (Dendroctonus ponderosae Hopkins) is a potential threat to eastern North American forests due to ongoing eastward range expansion through the boreal forests of Canada and a potential invasion pathway via movement of infested logs from western regions of the United States. The blue-stain fungi Grosmania clavigera and Ophiostoma montium are two of the most commonly found fungal associates of the mountain pine beetle. Transported phoretically, these fungi provide essential nutrients to developing larvae and may help beetles overcome resin defenses. In this study, we used species-specific primers to determine the presence of the two fungi of interest on mountain pine beetles collected from artificially infested logs of four potential new pine hosts for the insect found in eastern North America, eastern white (Pinus strobus), red (P. resinosa), Scots (P. sylvestris), jack (P. banksiana) pine, and two known hosts, lodgepole (P. contorta), and ponderosa (P. ponderosae) pine. Additionally, the fungi of interest were plated on malt extract agar media amended with sap wood derived from eastern white, red, Scots, jack, ponderosa, or Austrian (P. nigra) pine, and their growth rates were recorded. Our results provide additional insight into the invasion potential of mountain pine beetle into eastern North America, as novel host differences in fungal and thus beetle suitability may impact ultimate invasion success of this destructive insect.