Dispersal ability of marked, irradiated olive fruit flies [Bactrocera oleae (Rossi) (Diptera: Tephritidae)] in arid regions

The dispersal of marked, irradiated olive fruit flies originating from a hybrid laboratory strain was studied in an olive groove located in the arid regions of southern Israel. Release-recapture experiments (eight in total) were conducted throughout a period of 5months (July-December 2008). In each experiment, ca. 5000 flies were released. Recapture of flies was conducted using a grid of 30 yellow sticky traps set in expanding semicircles from the centre of release. Service of traps was conducted 3 and 15days after the release. Fly quality and adult food type (only sucrose and protein + sucrose) before release was also investigated. Results point at an average dispersal distance of marked, irradiated olive flies of ca. 50m. Pre-release adult diet did not affect dispersal ability. Fly recovery averaged ca. 3.5% during summer and ca. 1.5% during autumn. Most of the recovery concentrated during the first 3days after releases, suggesting low survival of the released flies afterwards. As inferred from circular statistics, direction of dispersal was non-random with a significant directionality to the north-west. Results are discussed in view of environmental temperatures and wind direction.