Patterns of Ips cembrae (Herr) infestation on trap and standing trees of European larch (Larix decidua Mill.)

Abstract

The large larch beetle, Ips cembrae, is a significant pest causing the death of larch. In 2020, the attack density of I. cembrae on larch trap trees and standing trees was evaluated using sample sections placed along the trunk. As a defensive measure against I. cembrae, trap trees were highly effective in both spring and summer. The attack density increased with increasing trap tree surface area/volume. Galleries were established evenly throughout the entire trunk including the thin upper portion. When the number of trap trees was low and their capacity full, a continual aggregation of adults occurred due to pheromone communication, leading to attacks on healthy standing trees in the immediate vicinity. It was found that I. cembrae attacked standing trees from the trunk base, with a continual colonization of the stem up to 70% of the tree height in a time-differentiated progression of development stages. The attack density of I. cembrae on standing trees was up to 40% lower than on the trap trees.