Identification of minor components of the pine caterpillar moth, Dendrolimus spectabilis sex pheromone: components, electrophysiological activity and field effects

Extracts from the sex pheromone gland of Dendrolimus spectabilis (Lepidoptera: Lasiocampidae) were analyzed by gas chromatography (GC) using polar and non-polar capillary columns. Apart from the identified sex pheromone, (Z,E)-5,7-dodecadien-1-ol (Z5,E7-12∶OH), the compounds (Z,E)-5,7-dodecadien-1-yl acetate (Z5,E7-12∶OAc) and (Z,E)-5,7-dodecadienal (Z5,E7-12∶Ald) were also found, the ratio of the three compounds being 100∶5.6±5.4∶3.2±1.8. Small amounts of Z5,E7-12∶OAc, Z5,E7-12∶Ald and trace amounts of Z5,E7-12∶OPr were also detected by gas chromatography analyses coupled with mass spectrometer (GC-MS) analysis in selected ion monitoring mode (SIM). Analyses of the gland extracts by means of GC with simultaneous flame ionization and electroantennographic detection (GC-EAD) showed that only Z5,E7-12∶OH elicited the antennal response. However, analyses of relatively higher doses of standard compounds by GC-EAD demonstrated that male antennae responded to Z5,E7-12∶OH, Z5,E7-12∶OAc and Z5,E7-12∶OPr, but not to Z5,E7-12∶Ald. Study of the relationship between dosage and electroantennographic (EAG) response showed that for dosages between 0.01 and 1 μg male antennae were most sensitive to Z5,E7-12∶OH followed by Z5,E7-12∶OAc and Z5,E7-12∶OPr. Field trials showed that a triple blend of Z5,E7-12∶OH, Z5,E7-12∶OAc and Z5,E7-12∶OPr attracted significantly more male moths than a single blend with alcohol, or a binary blend of alcohol and acetate or propionate. A blend of Z5,E7-12∶OH, Z5,E7-12∶OAc and Z5,E7-12∶OPr at a ratio of 100∶3∶25 was found to be the best attractant for capturing male moths. Addition of a certain amount of Z5,E7-12∶Ald had a repellent effect. These results suggest that Z,E7-12∶OAc and Z5,E7-12∶OPr are minor components of the sex pheromone of D. spectabilis while Z5,E7-12∶Ald is an antagonist to male D. spectabilis.