Seasonal variation in males' response to female sex pheromone in the olive fruit fly, Bactrocera oleae (Gmel.) (Diptera: Tephritidae) in northern California

The olive fruit fly is an invasive pest of olives in California. A female produced sex pheromone has been identified and has been used for monitoring male population density. Trapping studies began in late May 2007. In spring and summer we caught no males in pheromone traps. In November 2007, the experiment was slightly modified by using white pheromone-baited sticky traps instead of yellow traps to control for trap color as an attractant. In April 2008 we added Torula yeast-baited McPhail-type traps to confirm that flies are present in the orchard even when none are found in the pheromone traps. Males responded to female sex pheromone from April 10^th to May 15^th and were non-responsive later in the spring and summer. Peaks in male catches in pheromone-baited traps are not synchronized with peaks in male catches in yeast-baited traps. These surprising results led us to hypothesize that the male response to sex pheromone may vary seasonally. Laboratory studies of olive fruit fly courtship and mating behavior will increase knowledge of the sexual activity of the olive fruit fly and help us understand the results of our field trials. We will continue trapping through the year. Results may provide a foundation that could be used to develop mating disruption techniques, which have been studied to a very limited degree in Europe, but not in the US for this species.