Epsilon Archive for Student Projects

Abstract

Ips typographus (Coleoptera: Curculionidae, Scolytinae) is a pest species that mainly attacks Norway spruce (Picea abies L. Karst.) and can kill large volumes of spruce trees during outbreaks, leading to economic losses of great magnitude. A common practice to manage attacks is to remove recently killed trees and thereby remove the beetles. Spruce bark beetles are limited by natural enemies that can reduce bark beetle emergence by more than 83%.
The aim of this study was to investigate the emergence progression of Medetera spp. and bark beetles I. typographus in Uppsala Sweden together with recorded thermal sums of different sun exposures. This was done in an outdoor experiment where logs from bark beetle killed spruce trees were placed in emergence boxes with different sun exposure.
I report a lag of roughly 7 days between ≥ 50% cumulative emerged I. typographus and M. signaticornis. The difference in number of days until ≥ 50% had emerged was significant when comparing the two species. There was also a significant effect of treatment on both M. signaticornis and I. typographus (p=< .001, η²= 0.341). Three species of Medetera were identified and differences in emergence patterns were observed with M. signaticornis being the earliest (and most common species), M. pinicola next earliest and M. ambigua the latest emerging species. Thermal sums at 50% cumulative emerged Medetera spp. and I. typographus differed significantly.
This study reveals for the first time how I. typographus and Medetera spp. respond to accumulating thermal sums after overwintering. Results from this study gives an insight into how attacked trees should be managed to reduce the risk of removing natural enemies from the forest.