Use of the Sterile Insect Technique in an Area-Wide Approach to Establish a Fruit Fly-Low Prevalence Area in Thailand

The Mangosteen of Trok Nong subdistrict, Khlung district, Chanthaburi province in Thailand, represents a marketable production area of tropical fruits that has been faced with an exportation trade barrier because of the presence of and infestation by Bactrocera dorsalis , among other fruit fly species. Awareness of the degree of damage caused by fruit flies resulted in the creation of the fruit fly control group. After applications of the male annihilation technique (MAT), the aim of this group was to implement an area-wide integrated pest management (AW-IPM) program using the sterile insect technique (SIT) to establish a low-prevalence area of fruit flys. The control group was developed in Trok Nong in 2005. A MAT fruit fly management initiative was applied in 2006, followed by a SIT-AW-IPM research project during 2007–2012. A geographical information system (GIS) was used to map and delineate the action area, guide the release of sterile flies, and design a trapping network system. The white-striped strain of B. dorsalis was developed by the Thailand Institute of Nuclear Technology (TINT) in 2007, and sterile flies were released every 28 weeks over 2,590 hectares of tropical fruit plantations during 2008–2013. Quality control of sterile flies and trap inspections were 326 carried out weekly, and fruit sampling was conducted twice a month. In addition, orchard sanitation was carried out, alternative and wild hosts were regularly removed, and mass trapping and interception traps were applied as recommended. In 2013, four organizations supported the establishment of the low prevalence area under a SIT-AW-IPM program, which is a requirement for fruit export. A participatory action plan for fruit fly control was designed and supported financially, and technical backstopping was tasked to the relevant stakeholders. The wild strain of sterile B. dorsalis was then continuously released for 20 weeks each year. From 2015 to 2017, the action site was put under an International Atomic Energy Agency (IAEA) technical cooperation program to enhance agricultural productivity by supporting the production of commodities free of fruit flies that meet international standards. The genetic sexing strain (GSS) of B. dorsalis is currently under developing process by three collaborators: the Department of Agricultural Extension (DOAE), the TINT, and the International Atomic Energy Agency. The development of this strain will improve the efficiency of the SIT-AW-IPM program. The SIT, integrated with other environmental-friendly control techniques in an AW-IPM approach, has the potential to suppress B. dorsalis populations, while increasing the S/N ratio. Further efforts following the International Standards for Phytosanitary Measures could lead the area to reach the goal of obtaining a low prevalence status of fruit flies under National Plant Protection Organization certification.