Field bioassays of verbenone and conophthorin, potential interruptive semiochemicals of the northern spruce engraver, Ips perturbatus, were conducted in south-central and interior Alaska in stands of Lutz spruce, Picea xlutzii, and white spruce, P. glauca, respectively.  Results from these studies showed that 84%-(-)-verbenone and racemic trans-conophthorin acted synergistically to significantly reduce the response of I. perturbatus to attractant-baited Lindgren funnel traps. Three associated subcortical insects, Pityophthorus nitidulus (Mannerheim), P. recens Bright (both Scolytidae), and Lasconotus borealis Horn (Colydiidae) were attracted to traps baited with treatments containing conophthorin.  An associate, the predator Rhizophagus dimidiatus Mannerheim (Rhizophagidae), responded significantly to all treatments containing the I. perturbatus attractant. There was no evidence that verbenone attracted any associated subcortical insects, so field application of the conophthorin/verbenone interruptant is not likely to cause a replacement infestation by another stem-attacking insect. During the summer of 2004, five treatment groups of P. xlutzii (Kenai Peninsula) and P. glauca (Fairbanks) were established to test the efficacy of the interruptant semiochemicals in preventing tree mortality.  Treatments were replicated ten times and included unbaited and attractant-baited trees with or without verbenone and conophthorin, and a fifth treatment investigating the attractiveness of trees that had been previously stressed by application of Vapam.  Preliminary results indicate that the combination of verbenone and conophthorin is effective in protecting standing trees from attack by I. perturbatus in Alaska.