Bark beetle attack on host logs reduced by spraying with repellents

Colonization densities of the pine shoot beetle, Tomicus piniperda, and the ash bark beetle, Leperisinus varius, respectively, on bolts cut from Scots pine (Pinus sylvestris), and ash (Fraxinus excelsior) were significantly reduced after spraying the bolts with emulsion of synthetic verbenone or a plant oil containing predominately ipsdienone. In both bark beetle species, host odours play an important role in triggering aggregation behaviour while pheromones are of minor importance, if at all. In contrast, Ips spp. primarily aggregate in response to aggregation pheromones and spraying with verbenone or the plant oil, respectively, affected colonization of pine trap trees by Ips sexdentatus less strongly. While the plant oil had no effect, verbenone reduced the colonization to some extent.