Schlyter, F., Byers, J.A., Lfqvist, J., Leufvn, A., & Birgersson, G. 1988. Reduction of attack density of the bark beetles Ips typographus and Tomicus piniperda on host bark by verbenone inhibition of attraction to pheromone and host kairomone. pp. 53-68. In: Payne, T.L. and Saarenmaa, H. (eds.), Integrated Control of Scolytid Bark Beetles, Virginia Tech. Press, Blacksburg. 355 pp.

Abstract-- An effective regulation of attack density in a bark beetle attack would occur if individuals sought to avoid too close habitation with neighbours on the bark surfaces in order to avoid competition for food and space between their offspring. In aggressive species a positive regulation is known to be driven by the aggregation pheromone during the mass attack to overcome host-tree resistance, while a negative regulation leading to a switching of attack to nearby patches may depend on several factors such as a quantitative drob in pheromone signal, spacing behaviours on bark, and production of semiochemical inhibitors. Ipsenol (Ie) and verbenone (Vn), two oxygenated monoterpenes produced later during the attack in Ips typographus, have earlier been shown to inhibit attraction to synthetic aggregation pheromone. Verbenone has also been shown to inhibit attraction of Tomicus piniperda to its host kairomone. In the first two tests for Ips typographus, Ie and Vn were combined at a low dose, either as a single point source, or with multiple dispensers spread over Picea abies logs, but these treatments did not decrease attack densities. A direct application of Vn gave an 88% reduction in attacks. The fourth test used Vn alone at three different doses applied over the surface and showed a strong log-linear dose-response, with close to zero attacks at the highest dose. Two tests with Tomicus piniperda on Pinus sylvestris logs treated with Vn in a similar manner also showed significant reductions in attacks. We suggest Vn to be one of several factors involved in attack density regulation. The response of the two species to this compound is highly dose-dependent; thus, Vn shows promise for practical management by prevention of attacks when applied sufficiently.
Chemical Ecology