Volatile emissions in spruce could act as cues for bark beetle host selection

The last decades have been marked by an increase in spruce mortality, partially triggered by the European spruce bark beetle Ips typographus. More frequent extreme weather events presumably prompted by climate change have led to rising stress and susceptibility of trees, a fragility which the bark beetle can exploit for its advantage. One aspect of the beetles’ life cycle that is not fully understood is the selection by pioneer beetles of an appropriate hosts that allows successful infestation. While it is often suggested that volatile or olfactory cues determine the suitability of a tree as host and that beetles generally tend to attack weakened trees, methodological challenges in field studies have so far hampered progress in empirical process understanding. Here we present a methodological approach for quantification and qualification of volatile emissions in situ. The method consists from a mobile GC/MS which is implemented into a stem incubation chamber system. We report preliminary results of in situ assessment of volatile compounds emitted by spruce trees as a first step toward a better understanding in tree-insect interactions.