Bark beetle attack on host logs reduced by spraying with repellents.
Densities of Tomicus piniperda and Leperi[si]nus varius [Hylesinus varius] on bolts cut from Scots pine (Pinus sylvestris) and ash (Fraxinus excelsior) in Germany were significantly reduced after spraying the bolts with an emulsion of synthetic verbenone or a plant oil containing predominantly ipsdienone. In both bark beetle species, host odours played an important role in triggering aggregation behaviour while pheromones were of minor importance. By contrast, Ips species primarily aggregated in response to aggregation pheromones and spraying with verbenone or the plant oil affected colonization of pine trap trees by I. sexdentatus less strongly. While the plant oil had no effect, verbenone reduced the colonization to some extent.