Wind-borne immigration analysis of the 2015 re-invasion of Bactrocera dorsalis complex(Diptera: Tephritidae) on Amamioshima Island in Kagoshima Prefecture

Abstract

A re-invasion of the oriental fruit fly, Bactrocera dorsalis complex(Diptera: Tephritidae), occurred on Amamioshima Island, Kagoshima Prefecture, Japan in 2015, 35 years after the eradication of this pest in the prefecture was confirmed in 1980. To investigate the sources of possible wind-borne immigrations, trajectory analysis was performed. Based on monitoring data, a sample of the first trapping on the island was collected on June 30, 2015. Backward trajectories beginning over the trap location starting on June 29 reached over the northwestern part of Taiwan within 24 h. Forward trajectories from the northwestern part of Taiwan arrived over Amamioshima Island continuously throughout the period from June 25 to 29. Backward trajectories from Kumejima Island, an island near Amamioshima Island, where a male adult was caught on July 3, also passed over Taiwan. Backward trajectory analysis for Amamioshima Island from July to September was conducted to search for other possible immigrations, and the analysis suggested that air currents from Taiwan and the Philippines arrived over the island on August 15 and 25, respectively. These results, therefore, suggest that Taiwan is a possible source for wind-borne immigrations occurring before mid-August.