Attraction of Male Pine Sawflies, Diprion jingyuanensis, to Synthetic Pheromone Candidates: Synergism between Two Stereoisomers

The pine sawfly Diprion jingyuanensis Xiao and Zhang (Hymenoptera: Diprionidae) is a serious pest of Pinus tabulaeformis Carr. in the Shanxi, Gansu, Inner Mongolia provinces P. R. China. sex pheromone D. was shown to be propionate ester 3,7-dimethyl-2-tridecanol. Virgin females contained an approximate 1:3 blend precursors erythro-(2S,3S,7R/S 2R,3R,7R/S)-3,7-dimethyl-2-tridecanol threo-(2S,3R,7R/S 2R,3S,7R/S)-3,7-dimethyl-2-tridecanol, but exact stereoisomers were not determined. Males responded strongest two threo-isomers, (2S,3R,7R) (2S,3R,7S), electroantennogram (EAG) recordings, followed by significant EAG response diprionol (pheromone component similis), whereas remaining isomers (2S,3S,7S 2S,3S,7R) 3,7-dimethyl-2-tridecanol acetate isomer (one components pini) did elicit any increase antennal response. In field, strongly EAG-active (2S,3R,7R)-isomer alone only weakly (but significantly) attractive males at 100 µg, while equally EAG- active (2S,3R,7S)-isomer same loading 8–14 times more than alone. Traps baited with amounts threo-isomers ((2S,3R,7R) µg + µg) caught significantly traps other isomers, either or proportions isomers. Thus, considered as strong essential sex-attractant for males, weak synergistic sex-attractant. This one few examples responding stronger binary fashion single stereoisomer