Top-down view of a mixed forest with many dead trees, whose dead, bare branches appear white in between the green of the healthy trees.

Bark beetle ecology and host selection

Bark beetles are one of the major threats to coniferous forests. This trend is supported by changing climate. Advancing climate change leads to an increased occurrence of weather extremes. Severe droughts or windthrow can increase the vulnerability of spruce to bark beetles, therefore supporting increased mortality of forest. To address this timely threat, we are studying different intersections between the bark beetle Ips typographus and its host Norway spruce.

Bark beetle research is an established field dating back over 250 years ago. Although much is known about the physiology and behaviour of bark beetles, some aspects still remain unexplained. In particular, the mechanisms of host selection are not yet fully understood. It is known that the beetles prefer weakened and stressed trees when selecting a host. We investigate the relationship between vitality and olfactory signals by assessing volatile profiles of the vigorous and stressed trees. Therefore, we perform volatiles measurements in dynamic chamber systems with a mobile GC/MS supported by traditional laboratory techniques (adsorption tubes).

Furthermore, we investigate the influence of beetle infestation and windthrow on defensive compounds (phenolics) and sugars (NSCs) during dispersal and colonization phases of the bark beetles. In addition, we also assess the influence of secondary metabolism on growth and development in bark beetles by performing feeding assays.

View up a slope that was once forested. On the hillside, there are only isolated trees left; in between, uprooted trees lie on the ground, and the stumps of cut trees can also be seen.

© Marie Werner

On the left is a tree, a measurement devices with many cables is strapped to the stem. On the ground sits a big instrument. On the right, a woman with warm outdoor clothing is smiling into the camera, holding some of the cables attached to the tree.

© Linda Lehmanski

On the left a laptop sits on a forest floor, and right next to it is an instruments, a green rectangular box with large white buttons and a small screen. Both are connected with cables.

© Linda Lehmanski

Close-up of a piece of dead wood. Part of the bark has been removed, and the feeding tunnel of a bark beetle can be seen underneath. In the upper part of the image, you can see a hand in a blue laboratory glove holding a fine brush into the feeding tunnel.

© Sadia-Zaman Shormee

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