Two experiments evaluated the effect of baiting uninfested grand fir logs and trees undergoing initial attack by Scolytus ventralis LeConte with Pityokteines elegans (Swaine) pheromone, on the subsequent attack by both species. Two more experiments assessed the effect of synthetic bark oil, exo-brevicomin, and P. elegans pheromone on the response by each species to multiple-funnel traps baited with attractants for the other species. The pheromone of P. elegans on unattacked logs did not have an inhibitory effect on the attack by S. ventralis. However, trees attacked by S. ventralis that were baited with P. elegans pheromone just after attack, yielded significantly fewer S. ventralis progeny than the unbaited controls. Neither synthetic bark oil nor exo-brevicomin caused a significant change in the catch of P. elegans in traps baited with its pheromone, but the predator Thanasimus undatulus Say was caught in traps baited with (±)-ipsenol, (±)-ipsdienol and synthetic bark oil, and another predator, Enoclerus sphegeus F., was caught in traps baited with exo-brevicomin alone or in combination with ipsenol and ipsdienol. The results do not support the hypothesis that interference competition based on semiochemical communication occurs between the two species.

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