Sex pheromone of the African armyworm Spodoptera exempta (Lepidoptera: Noctuidae): identification of components of the Okinawan population and formulation for population monitoring
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In 2010, abrupt outbreaks of the African armyworm, Spodoptera exempta (Walker), occured on the Tarama, Iriomote and Kikai Islands in southwestern Japan. Analysis by gas chromatography-electroantennographic detection (GC-EAD) revealed two EAG-active compounds on male antenna in crude extract of virgin females. These compounds were identified as (9Z)-9-tetradecenyl acetate (Z9-14:Ac) and (9Z,12E)-9,12-tetradecadienyl acetate (Z9E12-14:Ac) in ca. 90:10 ratio by subsequent GC-MS analyses. (11Z)-11-Hexadecenyl acetate (Z11-16:Ac), which had previously been identified as a third component in the Kenyan population, was not detected. Binary blends of Z9-14:Ac and Z9E12-14:Ac at ratios between 99:1 and 90:10 showed a potent attractiveness in the field, superior to that of virgin females and comparable to that of the three-component formulation determined in Kenya. For the population survey, a 98:2 blend was used. In Tarama, only a few moths of S. exempta were captured with a light trap during the night when more than 600 males were captured with synthetic sex pheromone; more S. exempta captures with a light trap had been reported than with sex-pheromone traps in Kenya. This indicates that the Okinawan population has different properties from the Kenyan population in pheromone composition and behavioral response to light.
KeywordsSex pheromone Allopatric population Pheromone component Phototaxis
We thank Ayako Yamaguchi of the Miyako Substation of OPPPC and Naoki Haneji of the Tarama Village Office for cooperation in the collection of insects and operation of field experiments. Thanks are also due to Masahiro Taniguchi of Okinawa Prefectural Government, Keiji Yasuda of OPPPC for encouragement throughout the investigations and Serge Glushkoff for editing the manuscript.
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