Attacks of bark‐ and wood‐boring coleoptera on snow‐broken conifers over a two‐year period

Abstract

The attacks of bark‐ and wood‐boring Coleoptera on broken conifer stems after severe snow‐breakage in early 1988 were studied in autumn 1988 and 1989. The study included twelve stands in the county of Värmland in central Sweden differing in age and edaphic conditions. The tops on the ground as well as the remaining rooted stem stumps of 94 Picea abies and 61 Pinus sylvestris were inspected. The presence of living branches on the stumps strongly influenced the incidence of insect attack. All stumps without branches were attacked during the two‐year period, whereas only a few spruce stumps with more than ten branches and no pine stumps with more than five branches were attacked. On spruce stumps, the most frequently encountered Coleoptera were all scolytids, i.e. the species Pityogenes chalcographus, Hylurgops palliatus, and the genera Polygraphus, Dryocoetes, and Trypodendron. On pine stumps, Tomicus piniperda was the most common species. Most of the spruce tops and virtually all pine tops were attacked during the two‐year period, and most of these attacks occurred during the first summer. P. chalcographus, Dryocoetes, and weevils of the genus Pissodes were the most frequent Coleoptera on spruce tops. On pine tops, the dominant insects belonged to the genera Pissodes and Pityogenes.