Abstract
Frontalin, a synthetic pheromone, induces attacks by the spruce beetle (Dendroctonus rufipennis) on baited standing trees, in which most broods fail. The impact of baiting 100 randomly chosen trees was determined by estimating the beetle population in a 766-ha spruce forest. Attack density in infested bark was similar for wind-thrown and baited trees; however, 95% of attacks occurred on the former, which were more numerous and had greater attacked surface areas. In this forest, it is estimated that 34 frontalin-baited trees would have been required for each windfall to trap 90% of the beetle population.