(E)-Dodecen-3-yl-1 acetate – the main component of the sex pheromones of Scrobipalpa Ocelatella Boid – has been obtained by a three-stage synthesis from decanal and malonic acid. The overal yield of pheromone was 35% calculated on the initial aldehide. The decanol in methylene chloride with pyridinium chlorine chromate is oxidized to decenaldehyde (1), which further condenses with malonic acid in trans-3-dodecene (2) acid, by Knoevenagel mechanism. Reduction of the trans-acid (2) with lithium aluminum hydride results in trans-3dodecen-1-ol (3), which in acetylation with acetyl chloride in benzene converts it into the desired acetate trans-3-dodecenylacetate - the main component of the sexual pheromone of sugar beet mining moth. Testing preparative forms with the preparation obtained under field conditions showed that the substance synthesized in laboratory in the above scheme exhibits high biological activity for male beetle moths.