2008). In turn, counting I. typographus galleries on P. abies stems is the major limitation of using ‘TGF-beta assay natural traps’. The counting of galleries of this insect species is very labour-intensive because it requires precise debarking of tree stems combined with the simultaneous identification of galleries. Thus, in the majority of studies, the estimation

of the density of galleries is restricted to small plates of bark collected from various parts of stems (Yamaoka et al. 1997; Jakuš 1998; Göthlin et al. 2000; Grodzki 2004; Hedgren and Schroeder 2004; Erbilgin et al. 2006; Eriksson et al. 2005, 2006, 2008). Regrettably, the methods for estimating the I. typographus population density presented in the above mentioned studies are not based on statistical methods; they do not allow calculation of estimation errors and can therefore be very inaccurate. In order to estimate the population density of I. typographus using infested stems, statistical Selleck Erismodegib methods should be applied to estimate: (1) the total density of I. typographus infestation of P. abies stems (tree-level); (2) the population density of I. typographus in the area investigated (stand-level). Cell Cycle inhibitor The development of the statistically-based method less interfering into the forest ecosystem and possibly less labour-intensive would allow quick and accurate estimation of the population density of I. typographus. This type of method could be applied to

the most valuable natural areas placed under strict protection. Placing a larger number of Tangeritin pheromone traps and total debarking of dead trees in reserves and national parks is generally not possible. On the other hand, an analysis of the population dynamics of I. typographus in managed forests is an indispensable tool for carrying

out silvicultural treatments, improvement of forest management methods and implementation of conservation-oriented forestry. The outbreaks of I. typographus have been observed for a long time, in all Central and Northern European countries (e.g. Eidmann 1992; Peltonen 1999; Schröter 1999; Wichmann and Ravn 2001; Grodzki 2004; Gilbert et al. 2005). I. typographus mainly attacks weakened and fallen trees but; when it occurs in large numbers, it may also infest healthy trees after overcoming their defence mechanisms (e.g. Christiansen et al. 1987; Lieutier 2004). Wind-fallen trees reveal little or no resistance to beetle attacks allowing successful colonisation of their stems at low densities and thereby avoiding strong intraspecific competition (Anderbrant 1990). Hence, windfalls may result in a surplus of the breeding material, which in turn may lead to population outbreaks and subsequent attacks on standing healthy trees (e.g. Bakke 1989; Wermelinger et al. 2002). Among all types of forest damage in Europe, in the period 1950–2000, 2–9 million m3 per year of volume of trees infested by bark beetles, mainly I.