Identification of two aggregation pheromone components from female cypress bark beetles and evaluation of their activity in the laboratory and the field

Abstract

The cypress bark beetle, Phloeosinus aubei Perris (Coleoptera: Curculionidae, Scolytinae), is of increased concern in the European market of scale-leafed conifers (Cupressaceae). Surprisingly, its chemical communication has only scarcely been studied and no specific trap-based monitoring system is available for detection of flight of the adults. In order to unravel the pheromone communication channel, hindgut extracts of unmated females were analyzed by gas chromatography coupled to an electroantennographic detector (GC-EAD), using male antennae. The structure assignment of antennally active components was performed by gas chromatography coupled to mass spectrometry (GC/MS). Two antennally active compounds from gut extracts were identified as (–)-myrtenol and (–)-α-pinene by enantioselective GC/MS. Synthetic enantiomers of the identified components were tested separately by electroantennography. The attractiveness of different mixtures of these compounds was compared by a 4-arm olfactometer tests, followed by field trapping tests. To prove that the production of the compounds is related to reproduction, we pre-treated females with juvenile hormone III (JHIII). The gut extracts from these sexually mature individuals showed an elevated content of (–)-α-pinene compared to the control of untreated females. In olfactometer tests, 4:1 mixtures of racemic α-pinene and (–)- or (+)-myrtenol attracted both males and females in significant numbers. In the field tests using multifunnel traps a 5:1 mixture of (–)-α-pinene and (–)-myrtenol caught significantly more males and females than an unbaited control. These results are discussed in the context of the complex chemical communication system of cypress bark beetle.