2015 Volume 24 Issue 2 Pages 23-34
The oriental fruit fly and its relatives, Bactrocera dorsalis complex Hendel (Diptera: Tephritidae), were eradicated in Okinawa Prefecture in February 1986. No fruit flies were caught in monitoring traps in the next 7 months, but some have been caught every year since then. There are two possible routes of reinvasion: windborne immigration and accidental importation in infested fruits. To assess the risk of reinvasion by windborne immigration, we developed software that calculates forward trajectories from possible sources in Taiwan and the Philippines daily and their intersection with the islands of Okinawa. The reinvasion risk index on a particular day for an island is defined as the number of days when any trajectory from the possible sources passes over the island during that day or the previous 13 days. The trend of the risk index and the number of fruit flies caught in all the monitoring traps are graphed. Windborne immigration is considered possible when any oriental fruit fly is caught and the risk index is >0. The risk index is also mapped to show which islands face the risk. The index is automatically updated daily, making the software easy to use by plant protection officers in the field. At present, the system is used in Okinawa Prefecture and the Naha Plant Protection Office.
