Field response of the northern spruce bark beetleIps duplicatus(Sahlberg) (Coleoptera: Curculionidae, Scolytinae) to different combinations of synthetic pheromone with (−)-α-pinene and (+)-limonene

Abstract

Field trapping experiments were conducted to evaluate the response of Ips duplicatus (Sahlberg) (Coleoptera: Curculionidae, Scolytinae) beetles to different combinations of synthetic pheromone with the monoterpenes (−)-α-pinene and (+)-limonene. The addition of (−)-α-pinene to the pheromone led to a significant increase (by 36.3–47.8%) of I. duplicatus captures when the pheromone : terpene ratio was 1 : 40. When the ratio increased beyond 1 : 200, its synergic effect disappeared. Adding (+)-limonene did not modify the beetles response to pheromone for pheromone : terpene ratios of 1 : 40, 1 : 200 and 1 : 1000, whereas adding (−)-α-pinene and (+)-limonene in pheromone : terpenes ratios of 1 : 40 : 40, 1 : 200 : 200 and 1 : 1000 : 1000, respectively, caused a significant increase in captures by 61.6–254.1%. Therefore, doubling the quantity of released pheromone increased the attractiveness for I. duplicatus to 169.5–195.3%. Ips duplicatus has strongly intensified its response to the specific synthetic pheromone when (−)-α-pinene and (+)-limonene were released together. When the two monoterpenes were tested separately, the response to the pheromone was not modified by the presence of limonene, although it was slightly intensified in the presence of (−)-α-pinene.