Trade-off between attraction to aggregation pheromones and repellent effects of spike lavender essential oil and its main constituent linalool in the flour beetle Tribolium confusum

Essential oils of aromatic plants and their individual volatile components have been tested in pest management strategies for their toxic and often repellent effects on target insects. When evaluating their possible effects on crucial behaviours of the pest insects, the olfactory environment including intraspecific communication cues has to be considered. We used the flour beetle Tribolium confusum du Val (Coleoptera: Tenebrionidae), a common stored-product pest, to investigate the influence of oil of spike lavender, Lavandula spica Medik. (Labiaceae), and its main component, linalool, at various doses on olfactory-guided behaviour. Using four-way olfactometers, a dose-dependent repellent effect of L. spica oil and linalool alone was revealed. On the other hand, we confirmed that T. confusum is attracted by conspecifics, by means of an aggregation pheromone and by 10 ng of one of its components, 1-tetradecene. Twenty-four hour pre-exposure to 10 mu l of L. spica oil abolished subsequent attraction to 1-tetradecene and reduced attraction to five conspecifics. Simultaneous exposure to L. spica oil or linalool and five conspecifics reduced the repellent effect of the volatiles in a dose-dependent manner, whereas simultaneous exposure to 1-tetradecene at 10 ng abolished the repellent effect of L. spica oil only at a dose of 0.01 mg. These results indicate a dose-dependent trade-off between attractive and plant-derived repellent volatiles, which may influence the effectiveness of such volatiles in their potential use in alternative pest management strategies.