Bark beetles on logging residues of European larch: Effects of shading and diameter of logging residues on infestation density

Abstract

Ips cembrae, an important pest of European larch (Larix decidua), has caused local outbreaks in the last two decades and is becoming increasingly important as the proportion of European larch in forests increases. In 2021–2023, larch logs and piles of branches were placed into shaded forest and sunlit areas every month to study bark beetle species on logging residues. After adult emergence, the logs and branches were debarked, and the infestation density of bark beetles was analysed. The results indicate that shading, log diameter and top/bottom parts of log had a significant effect on infestation density of I. cembrae on logs. The infestation density of I. cembrae was higher on logs felled between December and June than on logs felled between July and November. Shading of branches was the most significant variable affecting the bark beetle species composition on branches. All four of the bark beetle species recorded were affected by diameter of the branches. Ips cembrae primarily infested sunlit branches while Cryphalus intermedius preferred shaded branches. In contrast, the infestation densities of Pityogenes chalcographus and Pityophthorus pityographus seemed to be affected primarily by moisture content of the branches.