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Psyche
Volume 2012 (2012), Article ID 321084, 7 pages
http://dx.doi.org/10.1155/2012/321084
Research Article

Declining Bark Beetle Densities (Ips typographus, Coleoptera: Scolytinae) from Infested Norway Spruce Stands and Possible Implications for Management

1Research Unit Forest Dynamics, Swiss Federal Research Institute WSL, Zürcherstrasse 111, 8903 Birmensdorf, Switzerland
2Department of Environmental System Sciences, Swiss Federal Institute of Technology ETH, ETH-Zentrum, 8092 Zürich, Switzerland

Received 15 September 2011; Revised 22 December 2011; Accepted 28 December 2011

Academic Editor: John A. Byers

Copyright © 2012 Alexander Angst et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

The eight-toothed spruce bark beetle (Ips typographus) is the most serious insect pest in Central European forests. During the past two decades, extreme meteorological events and subsequent beetle infestations have killed millions of cubic meters of standing spruce trees. Not all the infested stands could be cleared in time, and priorities in management had to be set. Natural or man-made buffer zones of about 500 meters in width are frequently defined to separate differently managed stands in Central Europe. While the buffer zones seem to be effective in most of the cases, their impact has not been studied in detail. Beetle densities were therefore assessed in three case studies using pheromone traps along transects, leading from infested stands into spruce-free buffer zones. The results of the trap catches allow an estimation of the buffer zone influence on densities and the dispersal of Ips typographus. Beetle densities were found to decrease rapidly with increasing distance from the infested spruce stands. The trap catches were below high-risk thresholds within a few hundred meters of the infested stands. The decrease in catches was more pronounced in open land and in an urban area than in a broadleaf stand. Designed buffer zones of 500 m width without spruce can therefore very probably help to reduce densities of spreading beetles.