Keele Research Repository

Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae) is an invasive worldwide pest of many agricultural, horticultural and ornamental crops. They are difficult to control because of their small size and high resistance to chemical insecticides. The aggregation pheromone of this species is currently used for monitoring, but the full potential for use of this and other pheromones has not yet been explored. Two male-specific headspace volatiles have been previously identified: neryl (S)-2-methylbutanoate which acts as an aggregation pheromone and (R)-lavandulyl acetate, for which the role is unclear. The roles of these compounds were studied to understand how they can be used in pest management. Laboratory bioassays showed that the aggregation pheromone, apart from being an attractant, also increased the activity level of adult F. occidentalis. This could be utilized to activate the thrips out of their concealed spaces within the crop and enhance pickup of chemical insecticides. (R)-lavandulyl acetate reduced the walking and take-off activity of adult females but increased the activity level of adult males. The possible role of this compound as a mating pheromone is discussed. The chemical analysis of male-exposed filter paper discs showed the presence of another compound, 7-methyltricosane, which was shown to act as a contact pheromone for species recognition. Adult females respond by raising their abdomen showing mating rejection towards adult males while abdominal wagging sideways was observed in adult males, a behaviour used in aggressive male-male interactions. This is the first identification of a contact pheromone in the order Thysanoptera.