The citrus fruit borer (Citripestis sagittiferella) is one of the most destructive pests of pomelo in the Mekong delta of Vietnam. In order to use synthetic sex pheromone as tool for monitoring the population dynamics, from which supplies information for timing control, the sex pheromone component of C. sagittiferella, (9Z,11E)-9,11-tetradecadienyl acetate (Z9,E11-14:OAc) compounds, was successfully synthesized by synthetic routes using Z selective Wittig reaction as key reaction and commercial 9-bromo-1-nonanol compound as starting reagent. Although the Z isomeric purity of the Wittig product [(9Z,11E)-9,11-tetradecadien-1-ol, Z9,E11-14:OH] was just about 94%, further excluding the E,E-isomer by stirring with tetracyanoethylene in THF at 39oC obtained almost pure Z,Z-isomer (>99% by GC-MS check). Consequnenly, the acetylation of the corresponding alcohol gave pure Z9,E11-14:OAc