Effect of the Living Host Tree (Picea) on the Response of Dendroctonus Rufipennis (Coleoptera: Scolytidae) and a Predator Thanasimus Undatulus (Coleoptera: Cleridae) to Frontalin and Seudenol

Two synthetic pheromones, frontalin and seudenol, were tested on living host ( Picea ) trees and on non-host ( Abies ) trees to determine their relative attractiveness to the spruce beetle ( Dendroctonus rufipennis ) and a clerid predator ( Thanasimus undatulus ). On host trees, frontalin attracted significantly more spruce beetles and induced significantly more attacks on the trees than did seudenol. On non-host trees, more beetles and a higher male ratio were attracted to seudenol than to frontalin. Frontalin has a positive effect on the behavior of female spruce-beetle attack, whereas seudenol has not. The resulting natural secondary attraction of attacking female beetles creates strong aggregation of both sexes of spruce beetles on host trees ( Picea ) baited with frontalin, but not on host trees baited with seudenol or on non-host trees ( Abies ). The clerid predator ( T . undatulus ) was attracted to frontalin in significatnly larger numbers than to seudenol.