ZLV Online

Abstract

The territory of Vítkov (Czech Republic) is characteristic of decaying spruce stands as a consequence of the increased gradation of the European bark beetle and the double-spined bark beetle. Due to the use of harvesting technology the forestry operations employ trap trees with branches (Norway spruce) as a defensive measure. In this paper, the attractiveness of trap trees was evaluated in relation to the time of their making. In 2015, once every fortnight (15.2., 28.2., 15.3., 31.3., 15.4.) trap trees with branches (2 units), and delimbed trap trees that meet the requirements of Czech technical standard ČSN 48 1000 (2 units) were placed; arranged in pairs, the minimum spacing was 10 m between each other. Invading bark beetles (the genus Ips) were analysed in individual trap trees, using entrance holes on four permanent spots fixed in the butt, mid-trunk, upper trunk and crown sections of the trunk. The examination was carried out in 7-day periods; the final inspection was combined with stripping the bark on each spot and checking the species of cambioxylophagous fauna. The abundance of spruce bark beetles was higher on delimbed trap trees, which were gained most significantly in the butt and mid-trunk sections while trap trees with limbs were more attractive in the upper trunk and mid-crown sections. Trap trees placed in March featured the greatest efficiency. The occurrence of double-spined bark beetles was not confirmed on the traps; traps with branches showed increased representation of the Ips amitinus bark beetle and the spruce wood engraver. The upper trunk sections provide comparable abundance of spruce bark beetles for both types of the trap trees. The change in terms of quality between the two types of traps involved moisture content in the phloem, not in the wood. Cluster analysis showed that the thickness of the section affects the difference between the traps in terms of invasion.