Interaction of Bark Beetles (Coleoptera: Scolytidae) and Root-Rot Pathogens in Grand Fir in Northern Idaho

Using explosives, 93 grand fir were examined for root decay and bark beetle activity. Ninety-six per cent of the trees attacked by bark beetles also had root rot. From the data it appears that root disease is an important factor in predisposing fir to attack by bark beetles. Significant relationships were found between the presence of root decay and both the incidence of beetle attack and the number of attacks. No such relationship could be found concerning the success of beetle attacks. The question of bark beetles as vectors of root disease was not considered.