Bactrocera papayae Drew & Hancock, Bactrocera philippinensis Drew & Hancock, Bactrocera carambolae Drew & Hancock, and Bactrocera invadens Drew, Tsuruta & White are four horticultural pest tephritid fruit fly species that are highly similar, morphologically and genetically, to the destructive pest, the Oriental fruit fly, Bactrocera dorsalis (Hendel) (Diptera: Tephritidae). This similarity has rendered the discovery of reliable diagnostic characters problematic, which, in view of the economic importance of these taxa and the international trade implications, has resulted in ongoing difficulties for many areas of plant protection and food security. Consequently, a major international collaborative and integrated multidisciplinary research effort was initiated in 2009 to build upon existing literature with the specific aim of resolving biological species limits among B. papayae, B. philippinensis, B. carambolae, B. invadens and B. dorsalis to overcome constraints to pest management and international trade. Bactrocera philippinensis has recently been synonymized with B. papayae as a result of this initiative and this review corroborates that finding; however, the other names remain in use. While consistent characters have been found to reliably distinguish B. carambolae from B. dorsalis, B. invadens and B. papayae, no such characters have been found to differentiate the latter three putative species. We conclude that B. carambolae is a valid species and that the remaining taxa, B. dorsalis, B. invadens and B. papayae, represent the same species. Thus, we consider B. dorsalis (Hendel) as the senior synonym of B. papayae Drew and Hancock syn.n. and B. invadens Drew, Tsuruta & White syn.n. A redescription of B. dorsalis is provided. Given the agricultural importance of B. dorsalis, this taxonomic decision will have significant global plant biosecurity implications, affecting pest management, quarantine, international trade, postharvest treatment and basic research. Throughout the paper, we emphasize the value of independent and multidisciplinary tools in delimiting species, particularly in complicated cases involving morphologically cryptic taxa. Bactrocera (Bactrocera) dorsalis (Hendel)

Two tephritid species namely the oriental fruit fly Bactrocera dorsalis Hendel and the guava fruit fly Bactrocera correcta Bezzi are considered to be the key insect pests of fruit production in Thailand, causing yield loss and quality degradation. This leads to poor commercialization in domestic markets and quarantine restrictions from importing countries. A decade of effective cooperation between Thailand's Department of Agricultural Extension (DOAE), the International Atomic Energy Agency (IAEA), and the Food and Agriculture Organization of the United Nations (FAO) has resulted in the implementation of an area-wide integrated fruit fly management programme which includes a sterile insect technique (SIT) component. The programme consists of two distinctive pilot areas with associations of smallscale mango growers covering 70 square kilometres in the Ratchaburi (western) and Pichit (northern) Provinces. The ongoing programme is aimed at controlling B. dorsalis and B. correcta through monitoring, orchard sanitation, selective application of bait sprays, and the release of sterile flies. Both species are mass-reared and sterilized at a facility located in Pathumthani Province following standard operational procedures described in this paper. The average weekly production during the mango season is 20 million B. dorsalis and 10 million B. correcta. After sterilization the pupae are transported weekly to the pilot areas, reared to the adult stage and ground-released at fixed release sites. Quality of the released sterile flies is monitored through the use of a trapping network to measure their distribution and abundance, whilst the success of the control is monitored using periodic fruit sampling to assess the percentage infestation. The integrated approach has been effective in controlling fruit flies by reducing damage from over 80% before programme implementation to an average of less than 3.6% in Ratchaburi Province in the past five years (2000 to 2004). Meanwhile, in Pichit Province where the control programme has been carried out for only two years (2003 and 2004), the infestation has been reduced from 42.9 to 15.5%. This preharvest suppression, combined with postharvest risk mitigation measures, has opened the possibility for exports of mango produced in these selected pilot areas to some of the most stringent and lucrative markets such as Japan. An economic feasibility study conducted in 2002 clearly shows that fruit fly control in Thailand using an integrated area-wide approach with an SIT component could be expanded to other production areas with significant economic returns.

The oriental fruit fly, Bactrocera dorsalis (Hendel), is a key pest that causes reduction of the crop yield within the international fruit market. Fruit flies have been suppressed by two Area-Wide Integrated Pest Management programs in Thailand using Sterile Insect Technique (AW-IPM-SIT) since the late 1980s and the early 2000s. The projects' planning and evaluation usually rely on information from pest status, distribution, and fruit infestation. However, the collected data sometimes does not provide enough detail to answer management queries and public concerns, such as the long term sterilization efficacy of the released fruit fly, skepticism about insect migration or gene flow across the buffer zone, and the re-colonisation possibility of the fruit fly population within the core area. Established microsatellite DNA markers were used to generate population genetic data for the analysis of the fruit fly sampling from several control areas, and non-target areas, as well as the mass-rearing facility. The results suggested limited gene flow (m < 0.100) across the buffer zones between the flies in the control areas and flies captured outside. In addition, no genetic admixture was revealed from the mass-reared colony flies from the flies within the control area, which supports the effectiveness of SIT. The control pests were suppressed to low density and showed weak bottleneck footprints although they still acquired a high degree of genetic variation. Potential pest resurgence from fragmented micro-habitats in mixed fruit orchards rather than pest incursion across the buffer zone has been proposed. Therefore, a suitable pest control effort, such as the SIT program, should concentrate on the hidden refuges within the target area.

The objective of this extensive series of experiments, involving more than 2800 field cage tests with potted mango trees, was to assess pre‐release supplements to enhance the mating success of sterile male Bactrocera dorsalis and Bactrocera correcta. We examined the effects of different pre‐release diets and methyl eugenol (ME), both independently and in combination. Tests were carried out more than 15 and 18 days for B. dorsalis and B. correcta, respectively, each day increasing the age of sterile flies. To evaluate the effect of different pre‐release diets on males, no‐choice mating tests were conducted with sterile males of increasing age and mature sterile females. Sterile males fed up to 2 days of age on sugar–yeast hydrolysate combinations achieved significantly more matings than males fed only water in B. dorsalis and more matings than males fed only sugar, only yeast hydrolysate or only water in B. correcta. To examine the effect of ME on mating performance, 2‐, 3‐, 4‐ or 5‐day‐old sterile males were given or not given access to ME for 1 h, followed by the sugar–protein diet until the day of the mating test. Mating performance tests were carried out with ME‐exposed and non‐exposed sterile males competing with mature wild males for wild females. Results showed a significant mating advantage of ME‐exposed over non‐exposed sterile males, although at younger ages they were still less competitive than wild males. The interaction of sugar–yeast hydrolysate diet and ME as pre‐release treatments for 2‐ and 3‐day‐old sterile males was assessed in terms of male sexual competitiveness. Overall, the combination showed an additive effect on increased mating success in B. dorsalis sterile males when competing a wild males for wild females, while in B. correcta males the drastic improvement in mating success was mainly linked to the ME exposure.

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Mating compatibility among recently colonized (wildish) populations of Bactrocera dorsalis (Hendel) from different geographic origins in Thailand was assessed through inter-regional mating tests. Outdoor octagonal nylon screen field cages containing single potted mango trees (Mangifera indica L.) were used. Sexual compatibility was determined using the index of sexual isolation (ISI), the male relative performance index (MRPI), and the female relative performance index (FRPI). The ISI values indicated that the northern population of Bactrocera dorsalis from Chiang Mai province was sexually compatible with the southern population of Bactrocera dorsalis (previously Bactrocera papayae) from Nakhon Si Thammarat province. The MRPI values showed that the northern males had a slightly higher tendency to mate than southern males, while the FRPI data reflected that females of both origins participated equally in matings. In all combinations there were no differences between homotypic and heterotypic couples in mating latency. Southern males tended to mate first with southern females, followed by northern males mating with northern females, while the latest matings involved heterotypic couples, in particular northern males mating with southern females. Overall, more couples were collected from higher parts of the field cage and the upper tree canopy, while there were no differences between the origins of flies in terms of elevation of couples within the cage. Laboratory assessments of fecundity showed no differences in the average number of eggs resulting from inter-regional crosses. Development of immature stages was also equal in the two hybrid crosses, with no differences found in the number of pupae produced, percentage pupal recovery, and percent adult emergence. The practical implication of this study is that colony of Bactrocera dorsalis derived from any northern or southern region of Thailand can potentially be used in sterile insect technique programs against this pest.

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