Feeding habits of Pityogenes chalcographus (L.) (Coleoptera: Scolytinae) on Norway Spruce (Picea abies) L. (Karst.) logging residues in wind-damaged stands in southern Poland

Abstract

The effect of deposition of logging residues (e.g. cut branches and tree tops) on infestation density and reproductive efficiency of the smaller European (six-toothed) spruce bark beetle, Pityogenes chalcographus (L.) (Coleoptera: Scolytinae), was studied on Norway Spruce (Picea abies) L. (Karst.) stands in southern Poland. It was found that such materials, originating from windbreaks and windfalls and spread loosely over the forest floor, were more readily infested by P. chalcographus than materials gathered in piles. However, the beetles achieved a significantly higher reproductive efficiency (number of new generation beetles per each parent individual) on branches in piles than on those spread loosely. In piles, the P. chalcographus infestation density, measured as the total number of individuals per square decimetre of bark area, and reproductive efficiency varied, depending on the location of the branches in a pile. The most favourable breeding conditions occurred in the middle layer of a pile. It was also found that at different infestation densities the method and placement of woody debris deposition did not affect the number of beetles that emerged. These results are discussed in the context of using logging residues as natural traps for bark beetles.