COMPETITIVE-EXCLUSION OF DENDROCTONUS-RUFIPENNIS INDUCED BY PHEROMONES OF IPS-TRIDENS AND DRYOCOETES-AFFABER (COLEOPTERA, SCOLYTIDAE)

We tested the feasibility of competitive exclusion as a potential mana gement tactic for the spruce beetle, Dendroctonus rufipennis Kirby, us ing pre-attack baiting with pheromones of 2 secondary species, Ips tri dens Mannerheim and Dryocoetes affaber Mannerheim. Spruce beetle attac k densities, gallery lengths per square meter, and progeny densities w ere significantly reduced by up to 78% in individual felled trees bait ed with the I. tridens pheromones (+/-)-ipsdienol and (-)-cis-verberno l, and the D. affaber pheromones (+/-)-exo- and (+)-endo-brevicomin, o r pheromones of both secondary species. A simplified D. affaber bait c onsisting of only (+/-)-endo-brevicomin also significantly reduced spr uce beetle attacks, resource exploitation, and progeny production. Bai ting with I tridens pheromones also reduced spruce beetle attack and s uccess in simulated patches of windthrown trees. Resource exploitation and indirect interference by synomonal inhibition of spruce beetle at tack are the most likely competitive mechanisms invoked. Competitive e xclusion of the spruce beetle may provide an alternative management ta ctic where traditional methods based on tree removal, widespread harve sting, and the use of insecticides are not feasible.