cis‐Verbenol and verbenone as male‐produced pheromone components of the cypress bark beetle, Phloeosinus aubei: Identification and behavioural tests in combination with the female‐produced pheromone components
Gábor Bozsik, Armin Tröger, Stefan Schulz, Gábor Szőcs Abstract
The need for monitoring the spread of the invasive cypress bark beetle, Phloeosinus aubei, a pest of scale‐leaved conifers across Europe, is urgent. The aggregation pheromone of females was reported earlier; however, an effective trapping method has not yet been developed.
Therefore, this study aimed to unravel the males' pheromonal communication system.
Volatiles produced by P. aubei males, as well as sex‐ and mating status‐specific extracts from mid‐ and hindguts of unmated and mated males and females were analysed by GC‐EAD, and compounds eliciting antennal responses were identified by GC–MS.
Two male‐specific pheromone components, cis‐verbenol and verbenone, were identified in the extracts from mated males. α‐Pinene, known to be a kairomone component, as well as the female‐produced pheromone (in a combination with (−)‐myrtenol), was also found in extracts of mated males. None of these components were found in unmated males.
Four‐arm olfactometer tests showed that females were attracted to the combination of (−)‐myrtenol, (−)‐α‐pinene and (−)‐cis‐verbenol, rather than to either (−)‐myrtenol or (−)‐α‐pinene alone. When this ternary blend was combined with (−)‐verbenone, the attractiveness for both males and females was reduced.
Female and male P. aubei spent significantly more time in the olfactometer arm containing (−)‐α‐pinene and (−)‐cis‐verbenol than in the control arms.
The ternary mixture of (−)‐myrtenol, (−)‐α‐pinene and (−)‐cis‐verbenol proved to be the most effective trap bait in the field, which could serve as a potent attractant for monitoring of P. aubei.