Spruce Beetle Aggregated by the Synthetic Pheromone Frontalin

Frontalin, a synthetic attractant developed from the southern pine beetle (Dendroctonusfrontalis Zimm.), induced spruce beetle (D. rufipennis Kirby) attacks on preselected spruce trees destined for harvest, and adjacent trees. If baited trees were treated with insecticide, spruce beetles and predators (Thanasimusundatulus Say) were killed. Female Dendroctonus predominated on frontalin-baited trees. Some baited trees, unprotected by insecticide, were killed by beetle attacks but many resisted attacks and prevented beetle broods from developing. Green windfall trees were attacked whether or not frontalin was used on adjacent standing trees. Distance between attractant, and attacked unbaited trees appeared to be related to tree size.