Components of the sex pheromone of the currant pug moth, Eupithecia assimilata, a re-emergent hop pest in UK

After an absence of 50 years, the currant pug moth, Eupithecia assimilata Doubleday (Lepidoptera: Geometridae), has reappeared as an important pest of hops, Humulus lupulus L. (Cannabaceae), in the UK. Pheromone gland extracts from virgin female E. assimilata moths were shown to contain (3Z,6Z)-cis-9,10-epoxyheneicosadiene (3Z,6Z-cis-9,10-epoxy-21:H) by gas chromatography linked to mass spectrometry. (3Z,6Z,9Z)-heneicosatriene (3Z,6Z,9Z-21:H) was also found as a minor component in one of two extracts. In field experiments, significant numbers of male E. assimilata moths were caught in traps baited with the (9S,10R)-enantiomer of 3Z,6Z-cis-9,10-epoxy-21:H but not in those baited with the (9R,10S)-enantiomer or racemic mixture. Addition of 3Z,6Z,9Z-21:H at the ratio present in gland extracts greatly reduced the attractiveness of the epoxydiene