Female sex pheromone of the Yunnan pine caterpillar moth Dendrolimus houi: first (E,Z)-isomers in pheromone components of Dendrolimus spp.

The Yunnan pine caterpillar Dendrolimus houi Lajonquière is a serious defoliator of coniferous forests in southwestern China. Gas chromatography-electroantennography (GC-EAG) analyses of extracts of female sex pheromone glands of D. houi moths revealed the presence of three compounds eliciting antennal responses. These were identified as (5E,7Z)-5,7-dodecadien-1-ol (E5,Z7-12:OH), (5E,7Z)-5,7-dodecadien-1-yl acetate (E5,Z7-12:OAc), and (5E,7Z)-5,7-dodecadienal (E5,Z7-12:Ald) by comparison of their GC retention indices, mass spectra, and EAG activities with those of synthetic standards. Average amounts of E5,Z7-12:OH, E5,Z7-12:OAc, and E5,Z7-12:Ald per calling virgin D. houi female were 14.7 +/- 12.9 ng (+/- SD), 5.8 +/- 5.4 ng, and 0.8+1.4 ng, respectively, in a ratio of 100:39.7:5.6. These three components were also collected from the headspace of calling virgin female moths by solid-phase microextraction (SPME). In addition, trace quantities of (Z)-5-dodecen-1-ol (Z5-12:OH), (5Z,7E)-5,7-dodecadien-1-ol (Z5,E7-12:OH), (5E,7E)-5, 7-dodecadien-1-ol (E5,E7-12:OH), (5Z,7E)-5,7-dodecadien-1-yl acetate (Z5,E7-12:OAc), (5Z,7Z)-5,7-dodecadien-1-yl acetate (Z5,Z7-12:OAc), and (5E,7E)-5,7-dodecadien-1-yl acetate (E5,E7-12:OAc) were tentatively identified in female pheromone gland extracts by selected ion monitoring GC-MS. Field trapping experiments showed that E5,Z7-12:OH, E5,Z7-12:OAc, and E5,Z7-12:Ald were essential for attraction of male D. houi moths. Traps baited with a 20:1:1 blend (alcohol/acetate/aldehyde) loaded on gray rubber septa were as effective as traps baited with virgin female moths. The optimum ratio of acetate to aldehyde was 1:1, and this ratio was more critical than the ratio of either compound to the alcohol. This represents the first example of (E,Z)-isomers in pheromone blends of Dendrolimus species.