Female sex pheromone of Ostrinia orientalis – throwing a light onthe relationship between O. orientalis and the European corn borer, O. nubilalis

Summary. The sex pheromone of Ostrinia orientalis(Lepidoptera: Crambidae) was analyzed by gas chromatography–electroantennographic detection (GC–EAD), GC–mass spectrometry and a series of bioassays. Three EAD-activecompounds were detected in the female sex pheromonegland extract, and identified as tetradecyl acetate (14:OAc),(Z)-11-tetradecenyl acetate (Z11-14:OAc) and (E)-11-tetradecenyl acetate (E11-14:OAc). The titers (ratio) of 14:OAc, Z11-14:OAc and E11-14:OAc in 3-day-old virginfemales were 0.49 ng (10), 4.86 ng (98) and 0.10 ng (2),respectively. In a wind-tunnel bioassay, the 98:2 blend ofZ11- and E11-14:OAc, but not Z11-14:OAc alone, elicitedthe same male behavioral responses as virgin females andcrude gland extracts. 14:OAc was inactive by itself, and didnot show any synergistic effect on the binary blend.Field trapping experiments also confirmed the attractivenessof the binary blend to O. orientalis males. Based onthese results, we concluded that the sex pheromone ofO. orientalis is a 98:2 mixture of Z11-14:OAc andE11-14:OAc. This sex pheromone is very similar to that of the Z-type European corn borer, O. nubilalis. The presentfinding raises the question of whether O. orientalis, which is indistinguishable from O. nubilalis based on external morphology,is a biologically distinct species independent fromO. nubilalis.