Identification of male produced compounds in the bark beetle Polygraphus subopacus and establishment of (Z)-2-(3,3-dimethylcyclohexylidene)-ethanol as an aggregation pheromone component

Joakim Bång,Martin Schroeder,Lina Viklund,Erik Hedenström

doi:10.1007/s00049-021-00358-0

Joakim Bång, Martin Schroeder + Show 2 more

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https://doi.org/10.1007/s00049-021-00358-0

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Abstract

Bark beetles of the genus Polygraphus have recently been involved in large bark beetle outbreaks in central Sweden, together with the European spruce bark beetle Ips typographus. Three species of Polygraphus can be found in this region; Polygraphus poligraphus, Polygraphus punctifrons and Polygraphus subopacus. Efficient pheromone traps would facilitate further investigations of these species and their role in bark beetle outbreaks. Pheromone compounds have previously been identified in P. poligraphus and P. punctifrons, but not in P. subopacus. Thus, we allowed males and females of P. subopacus to bore in the bark of stem sections of Norway spruce (Picea abies) in the laboratory. Volatile organic compounds from boring insects were sampled with SPME and analysed with GC–MS and several male-specific compounds were observed. The male specific compounds were 3-methyl-3-buten-1-ol, 3-methyl-2-buten-1-ol, 3-methyl-2-butenal, grandisol, fragranol, (Z)-2-(3,3-dimethylcyclohexylidene)-ethanol, (E)-2-(3,3-dimethylcyclohexylidene)-ethanol, (Z)-2-(3,3-dimethylcyclohexylidene)-acetaldehyde, (E)-2-(3,3-dimethylcyclohexylidene)-acetaldehyde, geranial and γ-isogeraniol. (Z)-2-(3,3-dimethylcyclohexylidene)-ethanol, [(Z)-DMCHE], was identified from GC–MS analysis to be the major male-specific compound while the (E)-isomer, [(E)-DMCHE], was found as a minor compound. These two compounds gave positive responses in EAG analyses with antennae from males and females of P. subopacus. Thus, (Z)- and (E)-DMCHE were used in a field experiment in central Sweden but only (Z)-DMCHE was found to be attractive to males and females of P. subopacus. Consequently, (Z)-DMCHE was established to be a component of P. subopacus aggregation pheromone.

Highlights

Some bark beetle species of the genus Polygraphus can cause considerable damage to their host trees
Polygraphus rufipennis is a pest on black spruce in North America (Bowers et al 1991) and Polygraphus proximus is a pest on Siberian fir in Russia (Kerchev 2014)
Polygraphus use aggregation pheromones to coordinate mass attacks on trees, and male-produced pheromone compounds have been identified for P. rufipennis (3-methyl-3-buten-1-ol, Bowers et al 1991), P. poligraphus [( −)-(R)-terpinen-4-ol, Schurig et al 1985, ( −)-(R)- and ( +)-(S)-terpinen-4-ol, Rahmani et al 2015] and for P. punctifrons [( +)-(1R,2S)-grandisol and ( −)-(R)-terpinen-4-ol, 1 3 Vol.:(0123456789)

Summary

Introduction

Some bark beetle species of the genus Polygraphus can cause considerable damage to their host trees. Polygraphus use aggregation pheromones to coordinate mass attacks on trees, and male-produced pheromone compounds have been identified for P. rufipennis (3-methyl-3-buten-1-ol, Bowers et al 1991), P. poligraphus [( −)-(R)-terpinen-4-ol, Schurig et al 1985, ( −)-(R)- and ( +)-(S)-terpinen-4-ol, Rahmani et al 2015] and for P. punctifrons [( +)-(1R,2S)-grandisol and ( −)-(R)-terpinen-4-ol,. Males of P. subopacus have been shown to produce acoustic signals when exposed to others males of the same species. These signals were found to be speciesspecific when compared to acoustic signals from Polygraphus proximus males and Polygraphus nigrielytris males (Kerchev 2020). P. subopacus is thought to occur only locally in the northern parts of Sweden (Ehnström and Axelsson 2002)

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