Attacks by bark- and wood-boring Coleoptera on mechanically created high stumps of Norway spruce in the two years following cutting

Abstract

Attacks of bark- and wood-boring beetles on mechanically created high stumps of Norway spruce, Picea abies L. (Karst.), were studied in the provinces of Dalarna (Grangärde area) and Uppland (Fagerön) in central Sweden. The experiment included a total of 362 stumps in the Grangärde area as well as 48 stumps and 18 logs at Fagerön. Most inspections were conducted in the first and second autumns following the cuttings made to create the stumps. All stumps were attacked by at least one species during the two-year period, and for almost all of them (95%) the initial attacks occurred in the first summer. The most frequently encountered species on the stumps were the scolytids Ips typographus (L.), Pityogenes chalcographus (L.), Hylurgops palliatus (Gyll.), Orthotomicus spp., Trypodendron lineatum (Oliv.), Dryocoetes sp. and Polygraphus poligraphus (L.), and the cerambycids Tetropium spp. and Monochamus sutor (L.). Both the time of cutting and stump diameter influenced beetle colonisation. I. typographus was not found in autumn-cut stumps, while Orthotomicus spp. was found more frequently in autumn-cut stumps than in spring-cut stumps. There was a positive relationship between I. typographus occupancy and stump diameter, while negative relationships were found between stump diameter and H. palliatus and T. lineatum occupancy. Most stumps (ca. 80%) were attacked by more than one bark- and wood-boring species in the first summer. The proportion of stumps attacked was significantly higher than the proportion of logs attacked for P. poligraphus, T. lineatum and Tetropium spp., whereas the opposite was true for I. typographus. The percentage of bark area utilised by I. typographus was significantly higher in logs than in stumps.