Anti‐attractant activity of (+)‐trans‐4‐thujanol for Eurasian spruce bark beetleIpstypographus: Novel potency for females

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.

Field effects of oxygenated monoterpenes and estragole combined with pheromone on attraction of Ips typographus and its natural enemies

“…In many cases, the beetles exhibited weak differences in response to the tested compounds in combination with the pheromone compared to the pheromone alone, and the observed effects were only marginally significant. However, there was a noticeable anti-attractive effect observed with 1,8-cineole, a compound for which similar findings and similar trends have been reported previously (Andersson et al, 2010;Binyameen et al, 2014;Jirošová et al, 2022b).…”

“…We used the pure enantiomers of (-)-carvone, (-)-terpinen-4-ol, (+)-pinocamphone, and (+)-isopinocamphone, which triggered a higher response on the I. typographus antennae (Schiebe et al, 2012;Hou et al, 2021;Kandasamy et al, 2023) and were commercially available or synthesized in the laboratory (Ganji et al, 2020). Experimental dispensers were designed in the laboratory, and their exact laboratory and field release rates were established using the gravimetric method and measured six times (Jirošová et al, 2022b) in a laboratory fume hood (temperature 25 • C and airflow 0.5 m/s) and in the field under the same weather conditions as the experiments (Table 1).…”

“…However, according to the primary attraction theory proposed by Lehmanski et al (2023), these compounds may play a role in helping male bark beetles detect weakened host trees, thereby facilitating successful colonization. Other compounds, e.g., 1,8-cineole and trans-4-thujanol, have proved to be potent anti-attractive compounds inhibiting beetle attraction to their pheromone (Jirošová et al, 2022b). 1,8-cineole has been identified as a potential predictor of bark beetle-resistant trees, along with several other specialized metabolites (Schiebe et al, 2012).…”

“…The activity of 1,8-cineole and trans-4-thujanol for I. typographus has been evaluated in a field trapping experiment using different doses in combination with pheromones. Both compounds demonstrated a similar level of dose-dependent anti-attractant activity, with trans-4-thujanol inhibiting more the captures of females than males (Jirošová et al, 2022b). These compounds have been tested in combination with other anti-attractants for the protection of spruce trees in various forest environments, such as fresh forest edges or fragmented forests (Jakuš et al, 2022;Jirošová et al, 2022a).…”

Ophiostomatoid fungi synergize attraction of the Eurasian spruce bark beetle, Ips typographus to its aggregation pheromone in field traps

“…However, in nature, fungi colonize the bark phloem and sapwood with a distinct nutrient profile containing high amounts of defense chemicals such as terpenes and phenolics. Recent studies showed that I. typographus —symbiont fungi metabolize the terpenes and phenolics and release a suite of VOCs that function as semiochemicals for I. typographus ( Kandasamy et al, 2021 ; Jirošová et al, 2022 ). Future studies should investigate the synergistic effect of the fungal VOCs on pheromone attraction by inoculating the fungal cultures on natural substrates, such as spruce bark phloem and sapwood.…”