Proceedings of 6th International Fruit Symposium 6–10 May 2002, Stellenbosch, South Africa pp. 223–232

The sterile technique for control of the oriental fruit fly, dorsalis (Hendel), in mango orchards in Ratchaburi Province, Thailand

M. Sutantawong1, W. Orankanok2, W.R. Enkerlin3*, V. Wornoayporn4 & C. Caceres4 1Office of Atomic Energy for Peace, Thailand 2Institute of Irradiation for Agricultural Development, Department of Agricultural Extension, Thailand 3Insect Pest Control Section, Joint FAO/IAEA Division in Food and Agriculture, Wagramer Strasse 5, P.O. Box 100, A-1400 Vienna, Austria 4Entomology Unit, FAO/IAEA Agriculture and Biotechnology Laboratory, Seibersdorf, Austria

Fruit are the main constraint to improving production and trade of fruits and vegetables in Thailand. Therefore, since 1987, the Department of Agricultural Extension (DOAE) in cooperation with the Office of Atomic Energy for Peace has run a pilot project for control of the oriental fruit fly (OFF), (Hendel),by integrating the (SIT) with other moni- toring and control methods in the mango-production areas in the Paktor District in the Ratchaburi province. The project includes mass-rearing and sterilization of OFF at the mass-rearing and steril- ization facility of the Irradiation for Agricultural Development Institute, DOAE, located in the Pathumthani Province and field releases of sterile flies complemented by bait sprays and a monitor- ing network of methyl eugenol baited traps. The International Atomic Energy Agency has pro- vided technical assistance since 1991 through a Technical Cooperation Project. The assistance has resulted in improved rearing and field operation activities. In the years 1999 and 2000, weekly ground shipments of 5–10 million sterile pupae were transported from the production facility in Pathumthani to Paktor District for ground release in 1120 ha of small commercial mango orchards. Quality control tests of the released sterile flies were routinely conducted. A trapping network of 25 methyl eugenol traps (2.2 traps/km2) was serviced weekly to monitor the distribution and abun- dance of the sterile flies released. Periodic fruit sampling was carried out to assess the impact of the control measures by determining the percentage fruit infestation. Infestation levels have been reduced from over 50% before the application of the integrated SIT,to an average of less than 4% in the past seven years (1994–2000) with a significant reduction to 1.3% in 2000. The mango growers in the area of the project have been exporting over 50% of their mango production to countries that do not require a fly-free certificate such as Canada, Hong Kong, Malaysia, Singapore, etc.,but discriminate against pesticide residues and fruit quality.Small volumes of mango have also been exported to Japan but only after attaining compliance with a post-harvest treatment and a Federal Phytosanitary Certificate.The economic benefits of SIT for the participating mango growers have been substantial.Farmers claim that mango has become a profitable business since the use of SIT for control of the key pest (i.e.OFF) and that mango growers in the neighbouring areas are eager to join the SIT project.An economic analysis projected over 14 years indicates a benefit to cost ratio of 7.5 to 1 and a net benefit of US$7.5 million for the mango growers of Paktor. This project has reached a stage where it could be scaled up to a national level with proper support from the govern- ment and mango industry. Despite the fact that this project is one of few examples of the rou- tine use of SIT for effective suppression of fruit flies,substantial improvements are needed in order to cost-effectively apply the SIT at a larger scale. The basic requirements for scaling up include: 1) strengthening of the management structure, 2) implementation of SIT on an area-wide basis for effective pest control and to allow economies of scale,3) scaling up the sterile fly rearing capacity to 300 million flies per week, 4) incorporating new and better technologies such as the aerial release of chilled adults, more environmentally friendly insecticide products for population suppression and use of female trapping systems, and 5) improving monitoring systems through the application of GPS/GIS for sterile fly release and operation of trapping networks.

INTRODUCTION yield reduction and market restrictions. Insecti- The oriental fruit fly (OFF), Bactrocera dorsalis cide applications to control fruit flies are done on (Hendel), is a major pest of fruits in Thailand a calendar basis and are widespread. Concerns causing annual losses to the fruit industry esti- about environmental pollution, undesirable mated in millions of dollars as a result of significant chemical residues and the preservation of bio-

*To whom correspondence should be addressed. diversity, demand new insecticide-independent E-mail: [email protected] strategies and technologies for combating fruit 224 Proceedings of the 6th International Fruit Fly Symposium flies. The sterile insect technique (SIT) is one such MATERIALS AND METHODS environmentally friendly technology. This technique has been highly successful in pest management Release area programmes in various parts of the world for The release area is situated in Paktor District, control and eradication of harmful insect pests, Ratchaburi Province, southwestern Thailand. It is a such as fruit flies, tsetse flies, screwworms and lowland area surrounded by areas under cultiva- certain caterpillars (IAEA 1999). The Department tion of field crops. Releases were made over of Agricultural Extension (DOAE) in cooperation 1120 ha of mango and other fruit crops. Subtropi- with the Office of Atomic Energy for Peace (OAEP) cal climatic conditions allow for a high diversity has the mango-production areas of Ratcha- and continuity of fruit hosts,making isolation virtu- buri Province since 1987. This pilot project in ally impossible. Ratchaburi has been assisted with technical cooperation from the International Atomic Energy Mass-rearing Agency (IAEA) of the United Nations since 1991. The mass-rearing and sterilization facility of the The SIT technology, including field activities and Agricultural Development Institute (IAD), DOAE, mass-rearing, sterilization and release of flies has located in Pathumthani Province has recently been been transferred through IAEA expert missions, upgraded to a production capacity of 30 million fellowships and scientific visits. In 1987 the govern- sterile OFF pupae per week. Current production is ment of Thailand decided to adapt some facilities 10 million per week. Adult flies are housed in sixty of the Centre for Irradiation of the DOAE into an rectangular cages constructed of an aluminum OFF mass-rearing and sterilization facility. Since sheet or plywood and covered with an insect that date the facility has been producing an screen (Vargas 1984), each cage containing average of 10 million sterile flies per week for the approximately 56 000 adults. The temperature of project. The IAEA Board of Governors recently ap- the adult rearing room is maintained at 26 ± 2°C proved an extension of the SIT Pilot Project for and relative humidity at 65–70%. The adult flies three more years (2001–2003). The technology are fed an artificial diet consisting of a 4/1 volumet- transfer has not been an easy task; however, after ric mixture of granulated sugar and ICN® yeast years of effort, it has paid good dividends to a hydrolysate (ICN Pharmaceutical, Cleveland, Ohio). small number of mango growers in the District of Water is supplied to the cages by a PVC tube with a Paktor, in the Ratchaburi Province. filter paper. Females start to produce eggs 10 days According to the information provided by the after emergence. Adults of the breeding colony DOAE and confirmed by one of the farmer associa- are kept for 28 days producing eggs, then the tions in Paktor District,the OFF damage decreased cages are replaced with newly emerged mass- from over 80% in 1987, before the implementa- reared adults. Female flies lay eggs during the day tion of the SIT project,to 30,26,21,18,17 and 9% in into perforated bottles, which are removed from the following six years (i.e. 1988 to 1993), respec- the cages for egg collection (Tanaka,1965; Steiner tively (Changjaroen et al.1996;Sri-arunothai 1998). & Mitchell 1966; Tanaka et al. 1970; Vargas 1989). From 1994 to 2001 the damage has been reduced The eggs collected are directly seeded into a wheat further to an average of less than 4%. bran-based diet (Tanaka et al. 1969). The composi- The economic benefits of SIT for the mango tion of the larval diet is presented in Table 1 and is growers of Paktor has been substantial. Farmers expressed in percentage of the total weight. The claim that mango has become a profitable business larval diet is prepared using a 250-l capacity since the use of SIT for control of the key pest (i.e. industrial mixer. Approximately 93 000 eggs are OFF) and that other mango growers are eager to seeded on the fibreglass tray (Model Fiber Glass®) join the SIT project. containing 6 l diet per tray. The trays are placed in The paper describes the project activities during a trolley and transferred to the initiation room with the 1999 and 2000 season and presents an a temperature of 27 ± 2°C and 90% RH. On the economic analysis of SIT use for suppression sixth day, after the transfer into the initiation purposes in the pilot area. This assessment is room, the diet trays are transferred to a lower unique in the sense that the economic returns of temperature room at 22 ± 2°C and held there the SIT project in Paktor, which started in 1988, are until the larvae are fully developed. The mature estimated and compared against the economic larvae pop out of the diet and fall into a metal returns of conventional control options and an tray filled with sawdust. The larvae pupate in the improved SIT control option. dry substrate. The pupae are separated from the Sutantawong et al.: SIT for control of oriental fruit fly in mango orchards in Thailand 225

Fig. 1. Sketch showing the oriental fruit fly release area in Paktor District, Ratchaburi Province. sawdust with a mechanical sifting device. The bags with pupae were packed into polystyrene sifted pupae are placed into the pupal trays, held containers and kept cool with ice packs.The pupae on racks and stored in the pupal storage room at were sterilized with 90 Gy of gamma radiation from 20 ± 1 or 27 ± 1°C. Quality control tests are con- a 60Co source before being shipped to Paktor Dis- ducted every time on fly ability and emergence, trict, Ratchaburi Province. Weekly shipments of sex ratio, egg hatch, and pupae weight following approximately 5–10 million pupae of both sexes the International Fruit Fly Quality Control Manual were transported by ground in a refrigerated (Anon. 1998; Wornoayporn 1999). truck and delivered directly to the SIT-treated area. Upon arrival at the release area, the bags with Sterile fly release pupae were taken out of the container and pupae Before irradiation, the pupae were marked with were placed in a wooden container (50 × 50 × 2 g of blaze orange fluorescent dye powder 2.5 cm), with 90 000 pupae per container. Six con- (Day-Glo®) per litre of pupae) two days before tainers were placed into a release hut. Twenty-two emergence. The marked pupae were packed into release sites were uniformly distributed in the 500-ml polyethylene bags, which were then release area (Fig. 1). A small sample of pupae was closed with rubber bands to induce anoxia. The systematically taken for quality control testing. Weekly releases were carried out at a density of Table 1. Formulation of the diet used for oriental fruit 10 700 pupae per hectare. fly at the Pathumthani mass-rearing facility (per 100 kg diet). Monitoring of populations Monitoring was based on trapping techniques Ingredient % (weight) and on fruit surveillance. Twenty-five monitoring Steiner’s traps baited with methyl eugenol and Wheat bran 26.0 insecticide were placed throughout the release Granulated sugar 12.0 area (Fig. 1). All the traps were inspected weekly. Brewer’s yeast 3.6 The flies were removed from the trap, identified Sodium benzoate 0.1 and recorded. Marked sterile flies in traps were Nipagin (methyl-p-hydroxybenzonate) 0.1 separated from unmarked flies using a microscope HCl 0.2 with a UV light source. Examination of trapped Water 58 flies consisted of identifying dye particles in the 226 Proceedings of the 6th International Fruit Fly Symposium

Table 2. Description of the different control options for oriental fruit fly in this study.

Option Description Damage level (%)

Conventional control Minimum orchard management is carried out by farmers. 50–80 (low input) Irregular pest control is done. Conventional control Moderate orchard management is carried out including 20–30 (high input) pruning, orchard sanitation and a conventional pest con- trol programme at orchard level. OFF control includes from 7–10 calendar insecticide cover sprays per season. SIT suppression on an Moderate orchard management is carried out including 1.5–6 orchard-by-orchard basis pruning, orchard sanitation, minimum level of population (status quo) monitoring, 1–2 insecticide sprays against OFF and permanent ground releases of sterile flies at orchard level. SIT suppression areawide Intensive orchard management is carried out including <1 (improved option) pruning, orchard sanitation, optimum level of population monitoring, permanent aerial releases of sterile flies in orchards and marginal areas. A government centralized management structure is in place where farmers actively participate in monitoring and control activities in the orchards and the government takes responsibility for activities in the marginal areas. body sutures, on the cuticle and on the ptilinum based on Thailand’s current inflation and interest in the head. Fruit surveillance was done through- rates. out the release area. A total of 500 mangos in Cost estimates.Three main sources of direct costs 1999 and 1700 in 2000 were collected and main- were identified as follows:1) production loss due to tained in plastic boxes to observe the emergence direct damage from pest, 2) costs of conventional, of OFF adults. current and improved control programmes and 3) market losses due to lack of comparative advan- Economic assessment tages to access the export market.For each control Methodology.Four control options were analysed: option the cost due to direct damage from pest 1) conventional control (low input),2) conventional was computed by multiplying the yield loss in control (high input), 3) SIT suppression on an tonnes per hectare by the farm gate price. A price orchard-by-orchard basis (status quo) and 4) SIT differential was used based on the current mango suppression area-wide (improved option). A brief prices for domestic market and for export markets description of the four control options is presented not discriminating against fruit flies such as the in Table 2. ones currently importing substantial amounts of For each option costs, benefits and economic mango from the pilot SIT project area (Singapore, indices were estimated using basic information on Hong Kong, Malaysia, Canada, etc.). The total current control practices, pest damage, produc- amount of mango lost due to direct damage was tion volumes and values, market shares, farm multiplied by 0.4 (40%) and by the average price gate prices in domestic and export markets and for domestic market (US$0.18/kg) to compute the macroeconomic indicators (i.e. inflation rates, value of the production lost that would have been interest rates). The information was provided by sold in the domestic market. The same procedure DOAE officials from the Ratchaburi Province and was followed for the share of the production lost by one of the mango associations in the Paktor Dis- that would have been sold in the export market trict where the SIT pilot project has been carried (60%). So in this case the amount lost was multi- out since 1988. For the control options analysed plied by 0.6 (60%) and by the average price for the flow of costs and benefits was estimated for a the export market (US$0.49/kg). Both figures time horizon of 14 years, which is the amount of were added to estimate the total value of the time that has passed since the project started back mango loss due to direct damage by the OFF. The in 1988.The total costs and benefits across 14 years total cost per year for the conventional control were discounted using a discount rate of 8% programmes included costs of insecticide treat- Sutantawong et al.: SIT for control of oriental fruit fly in mango orchards in Thailand 227

Table 3. Revenues obtained from the use of SIT against the oriental fruit fly in mango orchards (on an orchard-by-orchard basis) in the Paktor District in Thailand.

Year Damage Maximum yield Yield after damage Total area Price* Value (%) (tons/ha) (tons) (ha) (US$/ton) (US$ million)

1987 82 5 0.9 726 370 0.24 1988 30 5 3.50 726 370 0.94 1989 26 5 3.7 726 370 0.99 1990 21 5 3.9 726 370 1.05 1991 18 5 4.1 726 370 1.1 1992 17 5 4.2 726 370 1.1 1993 8 5 4.6 726 370 1.2 1994 1.7 5 4.9 726 370 1.3 1995 0.7 5 4.96 726 370 1.3 1996 1.6 5 4.9 726 370 1.3 1997 5.9 5 4.7 726 370 1.3 1998 5 5 4.75 726 370 1.3 1999 5.9 5 4.7 726 370 1.3 2000 1.3 5 4.9 726 370 1.3 Total – – – – – 15.6

*Weighted average for domestic and export prices based on 40% sales in domestic market and 60% sales in export market. ment against OFF (1–2 for the low input and 7 –10 Benefit estimates. For the conventional control for the high input per season), orchard sanitation options (low and high input) the only source of and pruning. For the status quo (SIT used on an benefits is the revenues obtained from the mango orchard-by-orchard basis) and improved option produced and sold in the domestic market as a (SIT used on an areawide basis) the costs included result of control actions against the OFF. In the costs of insecticide treatment against OFF (1–2 per case of the low-input control only 20% of the season), orchard sanitation, pruning, monitoring mango potential production is actually produced with methyl eugenol traps, fruit sampling and (i.e. a loss of 80%) and 70% in the case of the high- sterile fly release. In the case of the status quo input control option (i.e. a loss of 30%). This source only limited trapping and fruit sampling is carried of benefit also applies to the status quo and the out and sterile flies are ground released in orchards. improved control options. In the case of the sta- In the case of the improved option optimum tus quo option substantial revenues are obtained trapping,fruit sampling and aerial release of sterile from reducing OFF damage to less than an average flies on an areawide basis (inside and outside the 4% and to less than 1% for the improved option. orchard) was assumed. Market loss was computed In the case of the status quo SIT control option (i.e. by assuming that the conventional control options only used in orchards) which has been imple- do not have access to the more high-value export mented in Thailand since 1988 it is clear that OFF market compared to the status quo and the damage was gradually reduced;however,it took six improved option. There is a substantial loss in years before the damage was reduced from the potential revenues from not being able to export initial 80% to less than an average 4% per year. the fruit. For example, the mango growers in the The gradual reduction in damage levels and area where the SIT is being used are exporting 60% consequent increase in gross revenues is clearly of the production. This generates an annual gross shown in Table 3. For the improved control option revenue of US$1.2 million compared to US$0.6 (i.e.area-wide SIT), it was assumed that the project million if all the production was sold in the starts in year 2001 and that it would take three domestic market. No information on indirect costs years to reduce the current 4% damage levels to (i.e. environmental impact) including cost of less than 1%. It is also assumed that once the insecticide poisoning treatment for field workers, damage levels have been reduced below 1% (in secondary pest outbreaks due to natural enemy year 5) and insecticide sprays against OFF have mortality and reduction in honey production and been fully eliminated the price increases from pollination due to honey bee mortality was a weighted average of US$370/ton to US$540/ton included in the assessment. (i.e. a projected arbitrary increase of 45% in price) 228 Proceedings of the 6th International Fruit Fly Symposium

Table 4. Projected revenues from the use of SIT against the oriental fruit fly in mango orchards (on an area-wide basis) in the Paktor District in Thailand.

Year Damage Maximum yield Yield after damage Total area Price* Value (%) (tons/ha) (tons) (ha) (US$/ton) (US$ million)

2001 4 5 4.8 726 370 1.28 2002 3 5 4.85 726 370 1.30 2003 2 5 4.9 726 370 1.32 2004 1 5 4.95 726 370 1.33 2005 0.5 5 4.97 726 370 1.33 2006 0.5 5 4.97 726 370 1.33 2007 0.5 5 4.97 726 370 1.33 2008 0.5 5 4.97 726 370 1.33 2009 0.5 5 4.97 726 540 1.9 2010 0.5 5 4.97 726 540 1.9 2011 0.5 5 4.97 726 540 1.9 2012 0.5 5 4.97 726 540 1.9 2013 0.5 5 4.97 726 540 1.9 2014 0.5 5 4.97 726 540 1.9 Total – – – – – 22.0

*Weighted average for domestic and export prices based on 40% sales in domestic market and 60% sales in export market. In this case from year 9 (1995) due to a more effective application of the SIT which results in the complete elimination of insecticide use and assuming that the mango growers have managed to effectively negotiate a premium for the better quality fruit, the weighted average price increases from US$370/ton to US$540/ton. due to a premium paid by the clients.Table 4 pres- A value equal to 1 indicates that the control option ents the projected gross revenues for this control breaks even in the projected time frame and a option. Apart from this benefit (i.e. revenues from value greater than 1 indicates that the control increase in mango yields due to effective OFF con- option is economically viable and that for each trol) the status quo and improved options also monetary unit invested a profit margin is obtained. benefit from savings in insecticide use from the The net benefit is computed by subtracting the conventional control options and from being able total costs from the gross revenues.A value smaller to sell the fruit at a better price in the export than 0 indicates that the control option is not eco- markets. These more environmentally friendly nomically viable. A value equal to zero indicates control options also benefit from savings in envi- that the control option breaks even and a value ronmental cost. Unfortunately no information was greater than zero indicates that the option is viable available to estimate the value of this important and that a profit margin is being produced. The indirect benefit. The gross revenues (in US dollars pay-back period is the time required to pay for the million) were estimated for each control option by initial investment of the control option. For the adding the different sources of benefits. Having investment to be economically feasible the estimated the costs and benefits (gross revenues) pay-back period has to be obtained before the time for each control option the economic returns were frame of the project has expired (Enkerlin 2001). computed. Economic indices. To measure the economic RESULTS AND DISCUSSION feasibility of the four control options analysed three economic indices were calculated: 1) the Mass-rearing benefit to cost ratio, 2) net benefits (net present In 1999 and 2000,112.5 and 129 tons of larval diet value) and 3) pay-back period. Other important was used yielding c.959 and 872 millions of pupae, indices such as the internal rate of return (IRR) and respectively, resulting in an average production of thereturnonequity(N/K)werenotcalculatedsince 18 million pupae per week in 1999 and 16.7 million for all control options analysed the economic pupae per week in 2000. The average yield of returns are positive from year 1.The benefit to cost pupae and percentage pupal recovery in 2000 is ratio is computed by dividing the gross revenues lower than that in 1999. The high variability in by the total cost. A value smaller than 1 indicates pupal recovery is a result of not being able to that the control option is not economically viable. maintain stable conditions throughout the rearing Sutantawong et al.: SIT for control of oriental fruit fly in mango orchards in Thailand 229

Table 5. Average parameters of quality control tests for the oriental fruit fly at the Pathumthani production facility in 1999.

Year Egg hatch Pupal weight Pupal recovery Adult eclosion (%) (mg) (%) (%)

1999 78.6 ± 3.8 10.9 ± 1.3 47.1 ± 8.9 88.7 ± 3.8 2000 80.0 + 2.9 11.1 ± 0.5 46.7 ± 6.7 89.8 ± 1.9

Fig. 2. Average number (millions) of sterilized oriental fruit fly pupae released and estimated number of flies emerged during 1999–2000 (–•– pupae, — adults 1999; –¢– pupae, - - - adults 2000). process. Table 5 show the average of the results of tion to the Paktor District during 1999 and 2000. oriental fruit fly quality control test in 1999 and Adult eclosion and flight ability in the shipments 2000, respectively. arriving at Paktor was variable between shipments. The data from Pathumthani suggested that the Release shipment and handling contributed most to de- Figure 2 presents the number of sterilized pupae crease in adult eclosion and flight ability released during 1999–2000, and number of adults that emerged. Figure 3 show adult eclosion and Monitoring flight ability of flies after irradiation at the The ratio between released and native males was Pathumthani production facility and transporta- calculated from the captured flies from the traps.

Fig. 3. Adult eclosion and flight ability of oriental fruit fly after irradiation at the Pathumthani production facility and transportation to the Paktor District during 1999 and 2000 (–•– Pathumthani, — Paktor 1999; –¢–Pathumthani, - - - Paktor 2000). 230 Proceedings of the 6th International Fruit Fly Symposium

Table 6. The monthly ratio of oriental fruit fly sterile males to wild males captured in methyl eugenol traps in the Paktor District in 1999 and 2000.

Year Ratio of sterile males to wild males J FMAM J J A SO N D

1999 2.4/1 5.3/1 12.8/1 8.1/1 4.4/1 1.2/1 2.0/1 1.4/1 3.6/1 6.8/1 9.5/1 31.8/1 2000 33.7/1 9.6/1 2.2/1 1.1/1 1.1/1 1.6/1 3.0/1 3.5/1 6.8/1 10.0/1 45.2/1 112.3/1

The ratio of sterile males to wild males during Table 7. Percentage of mangos infested by the the critical months (September to March) was oriental fruit fly after releasing sterile flies in the Paktor acceptable considering that the aim of the District in 1999 and 2000. programme is population suppression and not eradication. The sterile to wild ratios were more Year No. of sampled % Infested fruits favourable in 2000 compared to 1999 (Table 6). fruits This resulted in a 5.9 and 1.3% fruit damage for 1999 and 2000 compared to over 50% before the 1999 559 5.9 use of SIT. 2000 1727 1.3 In total, 559 mangos were checked in the SIT area at Paktor from March–May 1999. Of these, around 2 ha of mango. So the total income for an 33 were found with live OFF maggots. During average farmer would be of only US$192/year, March–May 2000, 1727 mangos were inspected which is well below the annual minimum wage in for OFF damage. Of these, 23 were found with Thailand. live OFF maggots. The infestation rates in 1999 Conventional control (high input). Mango cultiva- and 2000 are presented in Table 7. tion under a high-input production scheme is done only on 4% (12 000 ha) of the total mango planted Economic assessment area in Thailand. Pest control, including the OFF, is Conventional control (low input). Mango produc- carried out through repeated insecticide treatments tion in Thailand under a low-input production in the form of calendar cover sprays during the scheme with minimum pest control activities is crops fruiting season. In the case of OFF, 7–10 common. As the economic figures indicate this is insecticide treatments are done to protect the basically a subsistence mango-production system crop throughout the season. This is an expensive where farmers operate at low costs and obtain a and ineffective control method that does not very low profit margin. If the mango orchards in provide farmers with any comparative market Ratchaburi where the SIT is currently being applied advantage. According to a group of farmers in would go back to a low-input production scheme, Thailand,mango growers that use this pest control in 14 years (i.e. time frame of the analysis), the scheme lose 30% of the crop despite the heavy total production cost would be US$0.79 million insecticide applications and have no chance to (US $78/ha/year), the gross revenues would be export their fruit because of insecticide residues US$0.98 million (US$96/ha/year), the benefit to and low quality of the fruit. cost ratio would be 1.2 and the net benefits If the farmers currently using the SIT to protect US$0.12 million equivalent to US$11.8/ha/year their orchards were forced to shift to a conven- (Table 8). The average farmer in Thailand has tional high-input pest control scheme based on

Table 8. Economic indices for the different control options for oriental fruit fly in this study.

Option B/C ratio Net benefits Gross revenues Cost NPV Pay-back NPV (US$ million) (US$ million) (US$ million)

Conventional control (low input) 1.2 0.12 0.98 0.79 NA Conventional control (high input) 2.3 1.9 5.9 2.6 NA SIT suppression: orchard-by-orchard 7.5 7.5 14.6 1.8 NA SIT suppression: area-wide 10.5 11.3 20.7 1.7 1 Sutantawong et al.: SIT for control of oriental fruit fly in mango orchards in Thailand 231

7–10 would be US$2.6 million (US$256/ha/year), tion areas of Paktor the economic analysis pro- the annual gross revenues US$5.9 million jected over 14 years indicates a benefit to cost (US$580/ha/year), the benefit to cost ratio 2.3 and ratio of 7.5 to 1 and a net benefit of US$7.5 million. the net benefits US$1.9 million equivalent to This is equivalent to an annual net benefit of US$187 per hectare per year. These economic US$738/ha, which is almost four times greater indices are favourable compared to the low-input than the net benefits obtained through the high- conventional control method described above. input conventional control options (Table 8). However, if compared against the status quo (i.e. Area-wide SIT (improved option). The proper use orchard-by-orchard SIT) and against the improved of the SIT for OFF control in the mango-production option (i.e. area-wide SIT) the economic indices areas of Paktor could further improve profits of are much less favourable, apart from the fact that mango production as the economic analysis this option would imply the need for intensive use shows. By using an area-wide approach the sterile of insecticides which would have adverse impact fly density currently used in the orchards of 10 000 on the environment and on food quality and most sterile pupae per hectare (c. 8000 adult flies/ha) likelynotbesustainableinthelongterm(Table8). could be reduced 8 times (to 1,000 sterile flies/ha). Orchard-by-orchard SIT (status quo). Only a very Part of the remaining sterile flies (another 1000 small fraction of the total farmers producing sterile flies/ha) would be released in the marginal mango in Thailand are currently benefiting from areas around the orchards to create an OFF buffer controlling the OFF through the SIT. The total zone. Still around 6000 flies per hectare would be mango area under SIT suppression is 1120 ha (7000 available to expand the SIT use to other mango- Rai) which is only 0.2% of the total cultivated area production areas in Paktor or elsewhere. Owing to in Thailand. The pilot SIT project in the Ratchaburi the more effective use of the sterile flies the cost Province started in the year 1987. It took six years of an area-wide SIT project would be practically before the OFF populations were effectively con- the same compared to the status quo. The cost of trolled. For example, in six years (1988–1993), in the current project has been estimated to be the mango-production area in the Paktor District in around 1.8 million dollars in 14 years compared to the Ratchaburi Province, damage was reduced US $1.7 million for an area-wide approach. The ef- from 80% before the project started to 8.5%. In fective use of SIT would reduce OFF damage to less the following seven years (1994–2000) the average than 1% greatly improving the gross revenues damage was reduced to less than 4%. The current compared to the status quo. An additional benefit pilot project in Paktor can be considered an eco- of the area-wide approach would be the complete nomic success for the mango growers despite the elimination of insecticide use (under the status fact that the SIT is not fully applied following the quo two insecticide treatments are applied per recommended technical procedures. For exam- season) and, apart from the savings from insecti- ple, field operations are not carried out following cide use, the mangos could be sold at a higher the area-wide approach, thus trapping and sterile price through a premium paid by the clients for fly release are done only at the orchards, sterile low insecticide residues and high quality fruit. flies are release by ground and in the pupal stage According to the economic analysis, for a 14-year instead of releasing by air and using the chilled time frame,the benefits to cost ratio for this control adult release method, the sterile fly densities are option is 10.5 compared to 7.5 under the status 10 times greater than the recommended rate quo, the net benefit US$11.3 million and the ini- (10 000 sterile flies/ha instead of 1000/ha), the tial investment would be paid in the first year trapping network does not include female traps (Table 8). The pay-back period in year 1 is possible and the densities are below the recommended basically because the major capital investment, levels and no systematic fruit sampling is carried which is the fruit fly factory, is already in place and out. This non-optimal use of the SIT makes the producing enough flies for the mango-production technology expensive and reduces its effective- areas in the Paktor District and because the major ness. However, even when the SIT technology is benefit, which is reduction of the current 4% not being properly used,OFF damage has dropped damage (average of the past seven years) to less to less than an average of 4% in the past seven than 1% and savings in insecticide treatments, years and farmers, by using an environmentally would be obtained in the first year considering the friendly technology, have found better prices for more than 10-year experience in the use of SIT their mangos in the export market. For the or- technology. Some capital will have to be invested chard-by-orchard SIT used in the mango-produc- in a packing and release centre.Equipment such as 232 Proceedings of the 6th International Fruit Fly Symposium vehicles,chilled adult release machine and GPS/GIS from the Insect Pest Control Section staff of the devices will have to be purchased, nevertheless, FAO/IAEA Joint Division, especially to Dr Jorge net benefits are positive from year 1 and increase Hendrichs and all recruited experts is much appre- gradually as the level of damage is reduced,insecti- ciated. We thank Mr Naicheng Xu, Project Officer, cide sprays are eliminated and the mango is sold at Technical Cooperation Department, for his effec- a better price in the export market. tive support. Finally, the programme could not have gone forward without the cooperation and CONCLUSIONS enthusiasm of the many growers and SIT program- The current SIT pilot project in the mango me staff who actively embraced the concept and orchards in the Paktor District has had a positive who have supported the activities of the many economic impact for the farmers despite the fact duties involved. that SIT has mainly been applied at orchard level rather than on an area-wide basis. Mango yields REFERENCES have substantially increased, insecticide spraying ANON. 1998. FAO/IAEA/USDA. A Manual of Quality Con- has been reduced by five fold and the export trol for Fruit Flies. IAEA Vienna, Austria. market to countries not discriminating against OFF CHANGJAROEN, P., DOKMAIHOM, R., FUNGVITTAYA, P., CHOORNPHURAT, C. & STAFF 1996. Fruit fly control has been opened due to the improved quality of by the sterile insect technique (abstract). In: 6th the fruit. Nuclear Science and Technology Conference, Bangkok, The profitability of the pilot project can further Thailand. 43. Ministry of Science Technology and improve if the project shifts from an orchard-by- Environment, Bangkok, Thailand. . orchard management approach to an area-wide ENKERLIN, W.R. 2001. An economic assessment for Oriental fruit fly control using the Sterile Insect approach and if the techniques used are updated Technique (SIT) in Thailand: a case study for the and optimized. mango production areas of Paktor District. IAEA, The positive economic impact of SIT technology Technical Cooperation Project THA5046. Vienna, on the mango producers of Paktor should be used Austria. to promote SIT at a national level. IAEA 1999. Entomology. In: The International Atomic The pilot project in Paktor should be converted Energy Agency’s Laboratories Seibersdorf. 18–20. IAEA, Vienna, Austria. into a model project and the SIT technology SRI-ARUNOTHAI, S. 1998. Area wide control of fruit fly transferred to the rest of the mango-production by the sterile insect technique. In: 7th Nuclear Science areas in Ratchaburi and rest of Thailand. and Technology Conference, Bangkok, Thailand. 47– The technology transfer should be done through 51. Ministry of Science Technology and Environment, a Government National SIT Suppression Programme Bangkok, Thailand. [In Thai.] with active participation of the mango industry. STEINER, L.F. & MITCHELL, S. 1966. Tephritid fruit flies. In: Smith, C.N. (Ed.) Insect Colonization and Mass Produc- tion. 555–583. Academic Press, New York. ACKNOWLEDGEMENTS TANAKA, N., STEINER, L.F., OHINATA, K. & OKAMOTO, R. The use of the sterile insect technique (SIT) for 1969. Low-cost larval rearing medium for mass control of the oriental fruit fly, Bactrocera dorsalis production of Oriental and Mediterranean fruit flies. (Hendel) in mango orchards in Ratchaburi Journal of Economic Entomology 62: 967–968. Province, Thailand, would not have been possible TANAKA, N. 1965. Artificial egging receptacles for the species of tephritid flies. Journal of Economic without the immense support of numerous organi- Entomology 58: 177–178. zations and individuals. Although we cannot list TANAKA, N., OKAMOTO, R. & CHAMBERS, D.L. 1970. all cooperators as authors, the authors wish to Methods of mass rearing the Mediterranean fruit fly gratefully acknowledge the following organiza- currently used by the U.S. Department of Agriculture: tions: International Atomic Energy Agency (IAEA), In: Proceedings of a Panel on Sterile-male Technique for Office of Atomic Energy for Peace (OAEP), Depart- Control of Fruit Flies. 19–23. IAEA, Vienna. WORNOAYPORN, V. 1999. Report on duty travel to ment of Agricultural Extension (DOAE), Office of Thailand, 26 March – 12 April, 1999. IAEA, Vienna, Agricultural Extension Ratchaburi Province, Office Austria. of Agricultural Extension Pichit Province, Office of VARGAS, R.I. 1984. Alternative egg collection system for Agricultural Extension Western Region. We are mass production of Mediterranean fruit fly (Diptera: also grateful to Mr Pramoed Raksarat, Mr Prarop ). Journal of Economic Entomology 77: Changjaroen, Dr Cherdchai Banditsingha, and Ms 1064–1069. VARGAS, R. 1989. Mass production of tephritid fruit flies. Renu Dokmaihom, for their commitment to and In: Robinson, A.S. & Hooper, G. (Eds) World Crop Pests, strong support of the project. Additionally, the 3B; Fruit Flies – Their Biology, Natural Enemies and technical support beyond what was expected Control. 141–151. Elsevier, Amsterdam.