Anti‐attractant activity of (+)‐<i>trans</i>‐4‐thujanol for Eurasian spruce bark beetle <i><scp>Ips</scp> typographus</i>: Novel potency for females
Anna Jirošová, Blanka Kalinová, Roman Modlinger, Rastislav Jakuš, C. Rikard Unelius, Miroslav Blaženec, Fredrik Schlyter
Abstract
BACKGROUND: Eurasian spruce bark beetles (Ips typographus) use both attractant and anti-attractant semiochemicals to find suitable mature host trees. Trans-4-thujanol is abundant in young, unsuitable spruce trees. Electrophysiological studies have demonstrated its high activity levels, but field data are lacking. RESULTS: Enantioselective GC-MS analysis showed that only (1R,4S)-(+)-trans-4-thujanol was present in Norway spruce bark volatiles. In a factorial design field-trapping experiment, trans-4-thujanol alone was not attractive to Ips typographus. Traps baited with I. typographus' aggregation pheromone and trans-4-thujanol or the known anti-attractant 1,8-cineole caught fewer beetles than those baited with the aggregation pheromone alone. Catches for trans-4-thujanol and 1,8-cineole were dose-dependent. Intermediate doses of trans-4-thujanol and 1,8-cineole had a similar effect. Surprisingly, in contrast to 1,8-cineole and other known Ips anti-attractants, which all inhibit males more strongly than females, the addition of trans-4-thujanol to the aggregation pheromone reduced the attraction of females more. CONCLUSION: The Norway spruce volatile (+)-trans-4-thujanol is a novel I. typographus anti-attractant with potency comparable to the known anti-attractants 1,8-cineole and verbenone, and is more effective for females than for males. Incorporating (+)-trans-4-thujanol into anti-attractant lures could improve protection of trees from mass attack by I. typographus.