Cold requirements to facilitate mass emergence of spruce beetle (Coleoptera: Curculionidae) adults in the laboratory

The spruce beetle, Dendroctonus rufipennis Kirby (Coleoptera: Curculionidae, Scolytinae), is a native disturbance agent of spruce (Picea spp.) forests in North America. Based on field observations, it is widely accepted that new adults must overwinter regardless of the length of the life cycle. We tested the effect of different lengths of time at 4° C on spruce beetle emergence. Our objective was to determine a protocol for rearing spruce beetle to facilitate laboratory-based research. We found that for spruce beetles from north–central Alberta and southern British Columbia, 70 d at 4° C led to rapid mass emergence of adults. Adults also emerged in the absence of a cold period, but over an extended period of time