The Douglas-fir Beetle in Minnesota: Locating an Indigenous Exotic in Northern Forests

摘要

Forest insects that are not native to a region can pose serious ecological threats to forest communities and serious economic threats to the forest products industry. The Douglas-fir beetle, Dendroctonus pseudotsugae Hopkins, and the eastern larch beetle, Dendroctonus simplex LeConte, are believed to have evolved from a common ancestor, whose populations likely became geographically isolated during the Wisconsin period of glaciation. Both of these bark beetles are capable of killing living host treesvia mass attack. The Douglas-fir beetle was recently detected in north-central Minnesota and concerns have been raised about the possibility of it becoming established in tree species native to Minnesota. We used two species of trap logs (Douglas-fir and tamarack) in combination with two pheromone baits: 1) frontalin (-9mg/day), seudenol, and ethanol and 2) frontalin (-3 mg/day), methylcyclohexenol, and ethanol, to attempt to determine whether there is a breeding population of the Douglas-fir beetle inMinnesota. In Minnesota, the eastern larch beetle successfully colonized cut logs of Douglas-fir, but we did not capture the Douglas-fir beetle. In a complimentary study in Montana, we found that the Douglas-fir beetle produced eggs in cut logs of tamarack when the logs were placed in an area infested by the Douglas-fir beetle.