Release-Recapture of Sterile Male Mediterranean Fruit Flies (Diptera: Tephritidae) in Southern California

A key determinant to the success of the Sterile Insect Technique (SIT) against the Mediterranean fruit fly (medfly), Ceratitis capitata (Wiedemann), is an even spatial distribution of sterile males following their release. While numer- ous studies have measured medfly dispersal, these almost always involve ground releases, whereas large-scale SIT programs release sterile males from small aircraft. The objective of the present study was to describe dispersal of sterile C. capitata males following aerial release in an urban area of southern California included in an ongoing SIT program. At present, adjacent flight paths are spaced 268 m apart (six flight lanes per 1.61 km [1 mi]), but in the face of potential budget cuts, flights may be reduced, which could result in increased distances between adjacent flight paths. We undertook this study to assess whether flight reduction might jeopardize the SIT program’s ability to achieve adequate ground coverage by sterile males. Dispersal of sterile males was monitored following four release flights made along a single 96.6 km east-west path between June 2011 and Febru- ary 2012. Data were gathered using traps located along six transects established perpendicularly to the flight path as well as detection traps routinely monitored as part of the management program. Data showed that (i) most males were captured within 268 m of the release line, although some males traveled > 1 km, (ii) there was a higher number of captures north of the release line, (iii) most males were captured within 3 d of release, although, compared to other studies, a large propor- tion (15%) were captured > 7 d after release. We discuss the implications of these findings and conclude that four flight lanes per 1.61 km would allow adequate coverage in the southern California SIT program