IDENTIFICATION AND BIOACTIVITY OF ALARM PHEROMONE IN THE WESTERN FLOWER THRIPS, FRANKLINIELLA-OCCIDENTALIS

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 ny mphs and adults responded to the pheromone by walking away from the so urce. The synthetic pheromone was active at a concentration of 1.0 ng, and the proportions of insects responding to the pheromone, but not t he distances moved, increased with increasing dose. Each component was active alone. although at low doses, the response to decyl acetate wa s less than to either dodecyl acetate or the blend. The pheromone also induced some second instars to drop from leaves and reduced ovipositi on by adult females in both two-choice and no-choice experiments. Beca use the response of western flower thrips to the alarm pheromone is re latively weak, the potential for its use in pest management is limited , unless it is used in conjunction with other control measures.