Sex pheromone of the fall armyworm, Spodoptera frugiperda: identification of a trace component that enhances attractiveness and specificity

The fall armyworm, Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae), is a polyphagous pest native to the tropical and subtropical Americas, but it has recently invaded the Eastern Hemisphere and spread rapidly. This migratory moth, which can fly long distances, now poses a global threat as a transboundary pest. To establish an efficient management program against this pest, monitoring of its occurrence is essential. Lures impregnated with four synthetic pheromone components of S. frugiperda - (Z)-9-tetradecenyl acetate (Z9-14:Ac), (Z)-11-hexadecenyl acetate, (Z)-7-dodecenyl acetate, and (Z)-9-dodecenyl acetate - are commercially available, and traps baited with them are used for monitoring. However, in Japan, these pheromone traps frequently capture many non-target moths, particularly Mythimna loreyi (Duponchel) (Lepidoptera: Noctuidae). We therefore reexamined the sex pheromone of S. frugiperda in an attempt to improve the monitoring lures and discovered trace amounts of (Z,E)-9,12-tetradecadienyl acetate (Z9E12-14:Ac) in female extracts at ca. 0.2% of the primary component (Z9-14:Ac). We verified its activity in males by field trap bioassays as well as antennal electrophysiology and demonstrated that this fifth component enhances the attractiveness of synthetic pheromones composed of the other four components to S. frugiperda and reduces the bycatch of M. loreyi. As Z9E12-14:Ac is found in pheromones of most Spodoptera species, it may have been a pheromone component in the common ancestor and played a key role in divergence of pheromone systems in the genus Spodoptera.