Identification and bioactivity of alarm pheromone in the western flower thrips,Frankliniella occidentalis

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Abstract
Analysis by gas chromatography (GC) and GC-mass spectroscopy disclosed that droplets of anal fluid produced by second-instar western flower thrips,Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae), contain a two-component alarm pheromone, comprised of decyl acetate and dodecyl acetate, in a molar ratio of approximately 1.5∶1. Both nymphs and adults responded to the pheromone by walking away from the source. The synthetic pheromone was active at a concentration of 1.0 ng, and the proportions of insects responding to the pheromone, but not the distances moved, increased with increasing dose. Each component was active alone, although at low doses, the response to decyl acetate was less than to either dodecyl acetate or the blend. The pheromone also induced some second instars to drop from leaves and reduced oviposition by adult females in both two-choice and nochoice experiments. Because the response of western flower thrips to the alarm pheromone is relatively weak, the potential for its use in pest management is limited, unless it is used in conjunction with other control measures.