Dryocoetes confusus (WBBB) is the most destructive insect pest of subalpine fir. Outbreak dynamics of D. confusus are closely linked to host susceptibility with beetles preferring old, large, living subalpine fir or trees that have recently blown down. Harvesting creates stand edges that are very susceptible to increased blowdown and potentially to increased WBBB activity. The amount of available and suitable host material on the forest floor is an attractive yet scarce resource. Results from this study show that the majority of trees falling in a natural sub-alpine fir stand are already dead, typically killed by the WBBB. Comparison of attack dynamics and brood production from downed, standing (no bait) and baited trees showed little difference among the three potential host resources. Baited trees had slightly higher attack densities, whereas naturally attacked trees had more advanced brood development and the beetles utilized a greater percentage of the total tree bole. Baiting concentrates attack into a discrete area but does not seem to artificially 'trigger' an outbreak or population expansion in the stand in subsequent years. WBBB populations are controlled by the availability of highly susceptible hosts and climatic conditions. Baiting is an efficient method of concentrating populations in an area for subsequent harvest. It will be a useful tool to incorporate in the management of sub-alpine fir forests.
Lorraine Maclauchlan, Julie Brooks.
Maclauchlan, Lorraine E., Stock, Arthur J.; Brooks, Julie E.. 2004. Attack dynamics and management implications of western balsam bark beetle in manipulated and natural subalpine fir ecosystems. Forest Investment Account (FIA) - Forest Science Program. Forest Investment Account Report