Abai, MR

6th International Congress of DipterologyLocal differences in the frequency and temporal pattern ofre-invasion of Bactrocera dorsalis complex (Diptera:Tephritidae) in Okinawa, southwestern Japan: Implicationsfor different invasion pathwaysOhno, S. (1), Y. Tamura (1), D. Haraguchi (1) & T. Kohama (2)(1) Okinawa Prefectural Plant Protection Center, Maji, Naha 902-0072, Japan(2) Okinawa Prefectural Agricultural Research Center, Makabe, Itoman 901-0336, JapanSince the Bactrocera dorsalis complex was eradicated from OkinawaPrefecture in 1986, the fruit flies have frequently re-invaded that area. Reinvasionssometimes caused outbreaks of the fruit flies and we have had toeradicate them again and again (e.g., Matsui, 1991). We compared thefrequency and temporal pattern of re-invasion of the flies between twomajor island groups within Okinawa, i.e., Sakishima Islands (SI) andOkinawa Islands (OI), which are geographically distant (>300km). Adultswere more frequently captured in SI by traps baited with a male-attractant,while outbreaks (detections of larvae infesting fruits) occurred morefrequently in OI. Annual trap catches tended to increase in SI, but not inOI. In SI, adults were captured most frequently in summer (June), whichcorresponds to adult seasonal occurrence in the neighboring countries suchas Taiwan. In contrast, peak catches in OI were observed in autumn(November); this pattern has never been found in other areas. These datademonstrate that the frequency of trap catches is not related to thefrequency of outbreaks, and that the temporal trapping pattern in OI isindependent from that in SI. The results are concordant with thehypothesis that re-invasions of the flies to SI and OI are caused mainly bynatural factor(s) and human-induced factor(s), respectively. Consideringthe proximity of SI to Taiwan (minimum distance 111km), the highertrapping frequency and its summer peak in that area may be explained bylong-range dispersal of adult flies. OI is exposed to higher risk of humaninducedinvasion of the flies because it holds the center of internationaltrade and tourism in Okinawa Prefecture. Such a human-induced invasion,especially via transportation of infested fruits, might have increased the183