Schlyter, F., Byers, J.A., Löfqvist, J., Leufvén, 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
