(Z)6,(E)8-HENEICOSADIEN-11-ONE - SYNERGISTIC SEX-PHEROMONE COMPONENT OF DOUGLAS-FIR TUSSOCK MOTH, ORGYIA-PSEUDOTSUGATA (MCDUNNOUGH) (LEPIDOPTERA, LYMANTRIIDAE)

Three candidate sex pheromone components, (Z)6,(Z)9-, (Z)6,(E)8-, and (Z)6,(E)9-heneicosadien-11-one (Z6Z9, Z6E8, and Z6E9) were identified in pheromone gland extracts of female Douglas-fir tussock moths (DFTM) , Orgyia pseudotsugata (McDunnough). Their occurrence in subnanogram q uantities in extracts and structural conversion during analytical proc edures and bioassays complicated chemical identifications. Complete id entification required comparative analyses of stereoselectively synthe sized and female-produced dienones by coupled gas chromatographic-elec troantennographic detection (GC-EAD), high-performance liquid chromato graphy (HPLC) and coupled GC-mass spectrometry (MS). Determination of the pheromone component was contingent upon an experimental design tha t minimized structural rearrangement of dienones before and during the field test. In a 40-min field experiment, acetonitrile solutions of e ach of the above dienones were carried on Dry Ice to traps and were sy ringed onto cotton release devices below trap lids. In combination wit h the previously known sex pheromone component of DFTM, (Z)6-heneicose n-11-one (Z6), Z6E8 was the only synergistic dienone and the mixture w as highly attractive. Because Z6 by itself attracts seven species of t ussock moths (two sympatric with DFTM), a blend of Z6 and Z6E8 may imp art specificity to DFTM pheromone communication. In commercial lures, this binary blend may facilitate species-specific, sensitive monitorin g and efficacious control by mating disruption of this important fores t defoliator.