The spruce bark beetle, Ips typographus, is an economically significant pest of Norway spruce (Picea abies) that preferentially infests and kills old trees. We looked for spruce volatiles that were perceivable by I. typographus and that differed as the host tree aged. Bark beetles were collected in the wild. Bark samples from spruce trees of different age were hydrodistilled. Gas chromatography–electroantennogram detection (GC-EAD) was used to identify which compounds induced beetle olfactory responses. These were identified by gas chromatography–mass spectrometry (GC-MS). Behavioural responses of bark beetles were tested using a Y-tube olfactometer. Several EAD peaks were recorded, of which trans-4-thujanol was consistently active and could be identified chemically unequivocally. The antennae of I. typographus females responded to a lower dosage of the compound than males, but both sexes were repelled by it. The bark of 10-year-old spruce trees contained 3 times more trans-4-thujanol than that of 35- 40-year-old trees, 27 times more than that of 70- to 80-year-old trees, and 200 times more than that of 120-year-old trees. Trans-4-thujanol is a bioactive compound in Norway spruce bark that varies in amount with tree age and affects spruce bark beetle behaviour under laboratory conditions. It is suggested that trans-4-thujanol might play a role in both spruce tree defence and tree choice by beetles.
Blažytė-Čereškienė L, Apšegaitė V, Radžiutė S, Mozūraitis R, Būda V, Pečiulytė D 2015. Electrophysiological and behavioural responses of Ips typographus (L.) to trans-4-thujanol—a host tree volatile compound. Ann. For. Sci.: 1-10. 10.1007/s13595-015-0494-5.
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