Responses by natural enemies to semiochemicals associated with mountain pine beetle (Dendroctonus ponderosae)

Abstract

Mountain pine beetle (Dendroctonus ponderosae Hopkins) is an aggressive bark beetle native to North America west of the Rocky Mountains and in the Black Hills of South Dakota. Outbreaks result in mortality to mature pines over many thousands of hectares. In western North America, mountain pine beetle’s primary hosts are ponderosa (Pinus ponderosae Lawson) and lodgepole (Pinus contorta Douglas) pines. In recent decades, ameliorating winter temperatures have allowed populations of mountain pine beetle to expand their range across the biogeoclimatic barrier of the Rocky Mountains into stands of jack pine (Pinus banksiana Lamb.) in Alberta, Canada. The invaded forest is contiguous with the boreal forest of eastern North America, creating concern that mountain pine beetle will expand its range toward the Great Lakes region where it threatens evolutionarily naïve red (Pinus resinosa Ait.), eastern white (Pinus strobus L.), jack, and scots (Pinus sylvestris L.) pines. Mountain pine beetles procure hosts by responding to species-specific aggregation pheromones. Natural enemies use these and other host volatile cues as kairomones. If mountain pine beetle were to expand its range into the Great Lakes region, it would encounter new forest and insect communities that are evolutionarily naïve to its presence. My thesis investigates semiochemical responses of native insects to chemical lures of mountain pine beetle within its native range and in the potential invasion zone. In addition, I study direct competitive interactions of mountain pine beetle with the native non-aggressive bark beetle, the eastern five-spined ips (Ips grandicollis Eichoff). My work suggests very few natural enemies native to the Great Lakes region will respond to the chemical cues associated with mountain pine beetle if it were to arrive so may not be significant mortality factors.