Proceedings of 6th International Fruit Fly Symposium 6–10 May 2002, Stellenbosch, pp. 131–141

South Africa’s fruit fly SIT programme – the Hex River Valley pilot project and beyond

B.N. Barnes1*, D.K. Eyles1 & G. Franz2 1ARC Infruitec-Nietvoorbij, Private Bag X5026, Stellenbosch, South Africa 2Entomology Unit, FAO/IAEA Agriculture and Biotechnology Laboratory, A-2444 Seibersdorf, Austria

Three species of fruit fly of significant economic importance occur in South Africa – Mediterranean fruit fly, Ceratitis capitata (Wiedemann), Natal fruit fly, C. rosa Karsch, and mango (marula) fly, C. cosyra (Walker). The first two infest all deciduous fruit, table grapes and most citrus fruits. C. cosyra occurs only in the subtropical northeastern parts of the country, infesting most subtropical and citrus fruits. South Africa’s deciduous fruit industry is centred in the , and has an annual export turnover exceeding US$450 million. In 1997 a pilot project to control fruit flies using the sterile insect technique (SIT) was implemented over an area of 10 000 ha in and around the Hex River Valley,where C.capitata makes up more than 99,9% of the fruit fly population. The goal was to suppress fruit fly populations in the Hex River valley to below the economic threshold in a cost-effective, ecologically compatible manner. Genetic sexing strains of C. capitata were used in a pilot facility to produce up to eight million sterile males per week. Aerial releases of sterile males started in the Hex River Valley in 1999. Good success was achieved despite many constraints and setbacks. High populations of C. capitata were substantially reduced, and fruit fly control costs, pesticide usage, and rejections of export table grapes due to tephritid fruit flies were also reduced. However, various factors highlighted problems experienced in a small, under-funded pilot rearing facility which resulted in below-normal sterile fly production. At the same time, inadequate ground control of wild fly populations in the release area emphasized the importance of good fruit fly host plant management in an SIT programme. An outbreak of C. capitata larvae in table grapes in the Hex Valley was initially suspected to have arisen from fertile females from the rearing facility, but was proven by DNA analysis to have most likely arisen from uncontrolled hotspots developing in wild host plants. Medium- to long-term goals for SIT are to commercialize sterile fruit fly production of both C. capitata and C. rosa, thereby expanding SIT to other production areas. With minimal government financing for the project, commercialization of SIT is considered to be the best means of sustaining viable SIT programmes in South Africa.

INTRODUCTION annum (Mumford & Tween 1997). The economic The South African export deciduous fruit indus- impact of Tephritid fruit flies country-wide has not try is of great economic importance to the coun- been determined. A third species, the marula fly try. Nearly 90 million cartons are exported annu- (also called mango fly), C.cosyra, occurs only in the ally, earning approximately US$450 million per subtropical northeastern parts of the country annum in foreign exchange. The Western Cape is and is a pest of certain subtropical fruits. the most important region for the production Fruit fly control in deciduous fruit orchards is of deciduous fruit,with about 58 000 ha under cul- based on ground applications of insecticides, tivation (Deciduous Fruit Producers' Trust, pers. either as full-cover organophosphate sprays or comm.). low-volume malathion and protein bait sprays. A The Western Cape is host to two species of fruit grower can make up to 27 applications annually, flies of economic importance, the Mediterranean depending on the programme followed, with fruit fly, Ceratitis capitata, and the Natal fruit fly, varying degrees of success. C. rosa.Between them they attack a wide variety of However, the greatest potential cost of fruit flies subtropical, tropical and deciduous fruits in this lies in the fact that they are internationally area (Annecke & Moran 1982). Further details of proclaimed quarantine pests and can thus restrict their occurrence, behaviour and management in the international trade in fresh fruit. This puts fruit the Western Cape is given by Myburgh (1964) and flies into a higher phytosanitary category than Barnes (1994). It has been estimated that crop other pests. South Africa is the only southern losses and control costs due to fruit flies in the hemispheredeciduousfruitexportingcountrythat Western Cape alone exceed US$3.2 million per is not either fruit fly-free, or does not currently *To whom correspondence should be addressed. have a large-scale area-wide programme to create E-mail: [email protected] †Present address: School Biological Sciences, University of fruit fly-free areas. It is generally accepted that Liverpool, Crown Street, L69 7ZB, U.K. the best method of achieving fruit fly-free status 132 Proceedings of the 6th International Fruit Fly Symposium is afforded by use of the sterile insect technique annum for SIT (Mumford & Tween 1997). Initially, (SIT). All of South Africa’s major competitors on the objective of the Hex River Valley pilot project the international fruit export market reap the was to eradicate Medfly from the area in order for benefits of exporting fruit from fruit fly-free areas the growers to benefit from exporting grapes from after following eradication programmes using SIT. a fruit fly-free area.However,it was realized early on Europe (South Africa’s traditional fruit export in the programme that the relatively small size of market) is scheduled to harmonize phytosanitary the area,together with limited funding,made erad- requirements with countries such as the U.S.A., ication an unrealistic goal.The objective was subse- which impose very rigid import restrictions on quently changed to cost-effective suppression of fruit from fruit fly-endemic countries. It is likely to Medfly using an environmentally compatible tech- become increasingly difficult for South Africa to nique. International experts in various SIT-related maintain its current market share after phyto- fields provided advice to the project management sanitary harmonization. Only with areas of low to team over a number of years. zero fruit fly prevalence will it be possible for Unlike SIT projects in most other countries, this South Africa to export large volumes of fruit to the feasibility project was not significantly supported U.S..A market and other fruit fly-free markets managerially or financially by government, and such as Japan under optimum shipping conditions, relied on funding from growers in the Hex River and to reap the benefits of increased foreign Valley,the deciduous fruit industry,the Agricultural exchange. Research Council, and the IAEA. The Western Cape Provincial Government later provided finan- SIT feasibility study cial assistance through irregular grants. A study to determine the feasibility of eradicat- ing or suppressing fruit flies using SIT was initiated Hex River Valley in 1997. It developed into the Hex River Valley The Hex River Valley (or Hex Valley as it is also SIT pilot project. SIT experts from the Interna- called) is a long narrow valley approximately tional Atomic Energy Agency (IAEA) in Vienna first 20 km × 5 km in extent. It is well isolated by visited the Western Cape in 1996. Owing to the mountains, with a single town () and valley-system of fruit production in the area, the one major national road running through the area was considered to be suitable for one or more valley. Some 90–95% of the cultivated area of SIT programmes. This led to the IAEA’s approval ±6000 ha was planted to table grapes, with the in 1997 of financial support for a project to deter- balance mainly comprising small areas of citrus mine the feasibility of eradicating or suppressing (‘easy peeler’ varieties). The greatest proportion of Medfly in the Western Cape. Management of the crops are exported. About 140 growers farm project was vested in the Pest Management Divi- in the valley. The many farmyards and associated sion of the Agricultural Research Council’s labourers’dwellings, together with the small town, Infruitec-Nietvoorbij Fruit, Vine and Wine Re- harbour a great many fruit fly host plants. It has search Institute in Stellenbosch (ARC Infruitec- been estimated that there are at least 1000 sepa- Nietvoorbij). rate host plant sites in the valley (J. Kriel, pers. The project started with a number of visits to the comm.). Western Cape by various SIT experts. An initial With the original objective of Medfly eradica- cost–benefit study identified areas that were tion in mind, two smaller areas outside the val- financially favourable for SIT (Mumford & Tween ley, each comprising approximately 1 500 ha of 1997). The study indicated that a SIT campaign table grapes farmed by about 20 growers, were covering all 19 fruit production areas in the included in the pilot project. The De Wet area, Western Cape would be cost-effective in the immediately outside the western end of the val- long-term. However, owing to the high cost of ley, was included as a buffer area to reduce the such a programme it was decided to implement likelihood of fertile fruit flies moving into the Hex SIT in a pilot project in the area identified by the Valley from this area. The Brandwag area, approxi- cost–benefit study as most favourable for SIT. The mately 10 km further west, was also included area chosen was the Hex River Valley, site of the because table grapes from this area were routinely largest production of table grapes in South Africa. sent through to the Hex Valley for cooling and sub- The study indicated that fruit fly control in this sequent transport to the docks. All area by conventional means cost US$127/ha per further reference to Hex Valley includes the De Wet annum, versus a projected cost of US$53/ha per and Brandwag areas unless otherwise specified. Barnes et al.: South Africa’s fruit fly SIT programme 133

Before the start of sterile fruit fly releases,the fruit trimedlure was deployed at a density of one trap fly control programme comprised a combination per 25 ha. After the initiation of sterile fruit fly of 2–3 full-cover sprays of organophosphate releases in October 1999, the Jackson traps were insecticide and seven to 15 applications of a mala- replaced with 222 McPhail traps baited with the thion and protein bait,which together cost approx- three-component food lure (Biolure®), at a density imately US$0.5 million per annum (Mumford & of one trap per 49 ha. Tween 1997; W. Botes, pers. comm.). From March 1997 all traps were inspected once a An SIT coordinator, two assistant coordinators, week on the same day and fruit fly species and three trappers and one bait applicator were ini- numbers were recorded. An effort was made to tially appointed to handle all field operations in rotate the traps within each block every 4–6 the Hex Valley. Later, two laboratory staff were weeks, although this was not rigidly adhered to. appointed to assist with fruit fly identification and Trap catches were graphed as the number of wild fruit sampling in a small laboratory. flies per trap per day. This article describes progress with the pilot pro- From 1997 to September 1999 inclusive, an ject, and looks ahead to the future of SIT in South area-wide baiting programme was in operation Africa. throughout the area of the pilot project. Bait applied to vineyards consisted of 700 ml of mala- MATERIALS AND METHODS thion 50% EC and 2 l of Nasiman® protein hydro- Funding and management of the pilot project lysate (48% a.i.) in 100 l of water, at 75 l bait per ha, Unlike SIT projects in most other countries, as permitted by the malathion label. Bait applied the Hex Valley pilot project was neither funded to non-crop fruit fly host plants in backyards and on nor managed by government. Mass-rearing of other non-crop areas comprised2lofmalathion sterile Medflies was carried out at ARC Infruitec- 50% EC and 10 l of Nasiman® in 100 l of water,at 15 l Nietvoorbij in Stellenbosch. Funding for sterile of bait per ha, as registered for non-crop hosts in fly production was provided through the SIT the Hex Valley. The bait was applied weekly as a Partnership–aformalagreement between the coarse droplet application. Applications were Agricultural Research Council and the Deciduous made by each grower individually, and the weekly Fruit Producers’ Trust to share costs on a 50:50 application programme was coordinated by basis.mm means of faxed reminders to each grower from Through intensive lobbying and publicity, the the SIT Coordinator in the Hex Valley. pilot project gained the support of 100% of the The SIT team in the Hex Valley was also advised Hex Valley growers. Funding for the field opera- to remove as many secondary fruit fly host plants tions in the valley was raised through a US$0.016 as possible, concentrating on backyards and trees levy on all export table grape cartons from the in other neglected areas in the town and on farms, area, which raised US$190 000 per annum (W. and to initiate a campaign to remove and destroy Botes, pers. comm.). This provided for all field all unharvested grape bunches in vineyards after operations in the Hex Valley, including the pur- harvest. chase and aerial release of the sterile flies, hiring of personnel, trapping equipment, laboratory Production of sterile fruit flies equipment etc. An old,disused building at the Pest Management Overall management of the pilot project was Division of ARC Infruitec-Nietvoorbij was refur- vested in the Pest Management Division of ARC bished and used as a sterile fruit fly production Infruitec-Nietvoorbij. Nevertheless, by virtue of facility. It was decided to use a genetic sexing the financial contribution made by the Hex Valley strain (GSS) where the females can be eliminated growers, they retained a significant degree of before mass-rearing.This results in greater cost-ef- independence in decisions made on, for exam- fectiveness as only the males are the active agent ple, the number of flies released per hectare per in SIT (Hendrichs et al. 1995). In such strains the week, management of trapping and baiting females carry a temperature sensitive lethal (tsl) programmes, host plant management, etc. mutation that allows them to be killed as embryos by heat treatment (Franz et al. 1994). In addition, Trapping and population reduction the females are homozygous for the mutation From 1997 to September 1999 inclusive, the white pupae (wp). This allows the integrity of the entire area was divided into 25 ha grids, and sexing system and the accuracy of the temperature a network of 360 Jackson traps baited with treatment to be monitored, and is required for a 134 Proceedings of the 6th International Fruit Fly Symposium

Filter Rearing System (Fisher & Caceres 2000). cial mass-rearing conditions. Mating compatibil- Mass-rearing started in April 1999 using the ity and competitiveness tests of the local wild Vienna 7-97 GSS obtained from the Entomology population with the GSS VIENNA 7-97 were carried Unit, FAO/IAEA Agriculture and Biotechnology out in Stellenbosch in field cages as well as in a Laboratory, Seibersdorf, Austria (Fisher 1999a). greenhouse at the IAEA laboratories. The experi- This strain was replaced in August/September mental protocol is described by Cayol (1998). 1999 with a refreshed GSS known as Vienna 7/Mix- 99 (Fisher 1999b), and was initially used for sterile Fruit fly sterilization and preparation male releases which started in October 1999. Male pupae were sterilized under anoxia one Owing to lack of space and funding, a Filter day before adult emergence (based on eye col- Rearing System to control the accumulation of our) using 90 Gy of 60Co in the ARC Infruitec- genetic recombinants (Franz 2002) in the tsl strain Nietvoorbij point-source irradiator. Pupae were was not initially set up. In April 2001, a new build- dyed with Day-Glo® fluorescent dye (Radiant Color, ing to house the adult colony and a quality control Houthalen, Belgium) and packed in paper bags in laboratory was erected, alleviating cramped rear- Plastic Adult Release Containers (‘PARC boxes’), ing conditions in the old building.Owing to genetic 110 ml pupae per bag (yielding approximately instability of the Vienna 7/Mix 99 GSS under the 4150 fliers/bag), seven bags per PARC box. Food local rearing conditions, especially in the absence for the flies was provided by means of cakes of of a Filter Rearing System, it became necessary to food grade agar plus sugar, placed onto gauze replace the strain three times between May 2000 vents on top of each box. Four to seven days and December 2001. The strains introduced, all after emergence (depending on the release fre- obtained from the IAEA Laboratory in Seibersdorf, quency) the PARC boxes were placed in a refriger- were Vienna 7/Tol 2000 in May 2000, Vienna 7/Mix ated truck at 4°C and transported approximately 2000 in October 2000,and Vienna 7-D53/Mix 2001 130 km to either the Worcester airfield for aerial in October 2001 (Robinson et al. 1999). In 2000 a releases, or in the case of ground releases, directly Filter Rearing System was set up to maintain to the release areas. genetic stability by eliminating the accumulation of the wrong-sex females in the release stream. Release of sterile fruit flies The target for production of sterile males was The Hex Valley SIT team decided on two release based on the requirements for the Hex Valley pilot rates during the year: 500 sterile males/ha/week project – five million per week (i.e. 500 sterile (five million/week over the whole target area) males/ha/week) during the growing season, and during the growing season period of October to one million per week (100 sterile males/ha/week) May inclusive, and 100 sterile males/ha/week during the winter/early spring.These release levels (one million/week over the whole area) during were set by the Hex Valley SIT team partly due to the winter/early spring months of June to Septem- a necessity to limit expenditure, but were below ber. the level of 1000 sterile males per ha per week From October to May sterile fruit flies were advised by SIT experts. released usually twice a week by air over the The rearing facility experienced a series of Hex Valley, on Tuesdays and Thursdays weather production problems during the period 1999 to permitting. A Cessna 207 was used, equipped the end of 2002, when the production targets of with a USDA chilled-fly release machine con- sterile flies were often not met. During many of trolled from the cockpit, and flying at 700 m these periods shipments of sterile Medfly pupae above ground level. A camera mounted under were imported from the El Pino Medfly Facility in the fuselage and focussed on the outlet tubes Guatemala, and some from the IAEA’s Seibersdorf enabled the release of flies to be monitored Laboratories, in an attempt to maintain in-season from the cockpit. The flight paths over all three releases at the required rate of five million sterile release areas were predetermined by GPS. Differ- flies per week. ent flight paths separated laterally by 1.4 km, were flown for the two release days each week,to ensure Mating performance of genetic sexing strain vs wild better distribution of sterile flies over time. The fruit flies starting point for releases was also varied each time The GSS of Medfly to be used in the pilot project for the same reason. was genetically different to the local wild strain in During the winter months from June to Septem- the Western Cape, and would be subject to artifi- ber, all releases were conducted on the ground, Barnes et al.: South Africa’s fruit fly SIT programme 135 as the smaller number of sterile flies did not jus- presence or absence of known genetic markers tify aerial releases. The paper bags of sterile flies present in the GSS flies in the Stellenbosch rear- were transported to the Hex Valley twice a week ing facility. on Tuesdays and Thursdays, where they were • Females exposed to the normal sterilizing dose distributed between the approximately 240 farms of 90 Gy were mated with fertile males and eggs in the three release zones, and in the town, con- collected for hatchability tests. centrating on the fruit fly ‘hotspots’, i.e. all back- • Malesandfemalesfromabatchofirradiated yards and around any neglected fruit fly host and (90 Gy) Medflies that was due to be sent to the shelter trees. Hex Valley were sent to an expert in the U.S.A. to determine their sterility status. Sterile/wild fly identification • Sexually mature and mated female Medflies All fruit flies found in the McPhail traps each from the same irradiated batch that was due to week were taken to the SIT laboratory in the be sent to the Hex Valley were placed in a large Hex Valley for identification. Two technicians, field cage containing some ripe peaches and trained by experts, identified the flies according to bunches of ripe table grapes. After several days species (C. capitata or C. rosa) and determined the fruit was inspected under a stereo-micro- whether the flies were sterile or wild on the basis scope and all eggs recovered kept to determine of the presence or absence of fluorescent dye hatchability. detected under a high intensity ultra-violet lamp • The dosimetry of the irradiator was checked by (UVP, Cambridge, U.K.). Where the dye was not an independent consultant from the National immediately evident, the heads of suspect flies Accelerator Centre (iThemba Labs) at Faure, were crushed, slide-mounted, and checked for the Western Cape. presence of dye under a compound microscope • Irradiation procedures for all suspect batches of equipped with an ultra-violet light. All flies deter- Medflies irradiated at the Infruitec irradiator mined not to have dye present were classified as from early November to end December 2001 wild flies. were audited for possible irregularities.

Infestation outbreak in 2001/2002 RESULTS AND DISCUSSION During the latter part of 2001 up to 30% of the weekly consignments of sterile Medflies sent to Funding and management of the pilot project the Hex Valley were females,due to genetic recom- The fact that project management and decision- bination of the GSS resulting in ‘wrong sex’ pu- making was decentralized between ARC Infruitec- pae (i.e. females in brown pupae). In December Nietvoorbij, the SIT Partnership, and the Hex Val- 2001, an outbreak of Medfly larval infestation in ley SIT team,and that project funding was effected table grapes in the SIT area was reported by the through various agencies (including growers in Hex Valley SIT team. The infestation was ascribed the Hex Valley), compromised the success of the by both Hex Valley growers and the Hex Valley project. Some decisions made by the Hex Valley team to unsterilized Medfly females included in team were prompted by economic considerations deliveries from the rearing facility. The Hex Valley rather than on what was best for the technology. team further alleged that females showing traces An example was the decision to release 500 sterile of the fluorescent dye (i.e. originating from the males per ha per week instead of the recom- rearing facility) had been dissected and consid- mended 1000 per ha per week, and to reduce ered to be fertile. releases in winter to 100 per ha per week. In an attempt to determine the origin of the A further compromising factor was the decision female flies that resulted in the infestation, the that baiting operations and vineyard sanitation following investigations were undertaken: would not be centrally coordinated, but left up • Infested grapes were collected from seven to individual growers. With approximately 240 different sites in the three main areas in the Hex growers involved, effective coordination and Valley, brought to ARC Infruitec-Nietvoorbij in supervision of field activities was seriously com- Stellenbosch, and placed on vermiculite in a promised. As a result, wild host plant manage- breeding room. All fruit fly pupae recovered ment, so critical in an SIT programme, was inade- from the grapes were couriered to the Entomol- quately addressed. This is partly reflected by the ogy Unit at the IAEA Laboratories in Seibersdorf high Medfly populations prior to sterile releases, for mitochondrial DNA analysis to determine the and the increasing wild fly populations and fruit 136 Proceedings of the 6th International Fruit Fly Symposium

Fig. 1. Numbers of wild Medflies caught in the Hex Valley during the baiting campaign before (a) and after (b) releases of sterile flies. infestation after releases. The latter was, however, sterile releases (Fig. 1b). exacerbated by inadequate numbers of sterile flies During the period 1997 to 1999, before sterile being produced by the facility. releases, wild Medfly populations were highest in The overall success of the project would almost late summer/autumn (from March to end-May) certainly have been greater had the project been when peaks of between four and six flies per adequately funded and managed by a single trap per day (FTD) occurred (Fig. 1a, Table 1). agency. During this period the mean annual FTD varied from 0.9 to 1.0. It was evident that the baiting Trapping and population reduction programme was unsuccessful in reducing the Figure 1 shows the numbers of wild Medflies populations prior to releases of sterile males in caught in the Hex Valley during the baiting cam- October 1999. This is ascribed to i) the relatively paign before sterile releases started in October weak protein component of the legally-permitted 1999 (week 40) (Fig. 1a), and for three years after bait solutions which did not adequately attract

Table 1. Peak and annual mean flies per trap per day (FTD) in the Hex River Valley before and after the releases of sterile Medflies.

Before releases After releases 1997 1998 1999 2000 2001 2002

Peak FTD 4.14 5.91 3.97 1.20 1.76 2.76 Mean FTD 0.85 1.03 1.03 0.14 0.20 0.38 Barnes et al.: South Africa’s fruit fly SIT programme 137

Fig. 2. Production of sterile male Medflies at the Infruitec-Nietvoorbij mass-rearing facility between October 1999 and December 2002 (two-week moving average). fruit flies, and ii) inadequate area-wide coordina- did not heed the request to remove backyard tion of bait applications in the release area. hosts and unharvested grape bunches (W. Botes, After the start of sterile releases in October 1999, pers. comm.). Baiting of host plants was also the peak wild fly population levels decreased ineffective, resulting in a many suitable sites for substantially in 2000 (Fig. 1b, Table 1), to 0.14 FTD, fruit fly survival, especially during the summer/ representing a six- to seven-fold decrease in the autumn period when fruit fly populations nor- wild fly population. During the next two years, mally reach a peak. however, wild fly populations steadily increased, but still remained well below levels prior to re- Production of sterile fruit flies leases. Fruit fly larval infestation of table grapes Sterile Medfly production fluctuated widely, in the release area during the main harvest period seldom exceeding one million sterile males per (December to March) was also reported during week for the first 16 months of operation. It was 2001 and 2002 (W. Botes, pers. comm..n). Most only after November 2001 that production started infestation was reported from the two smaller SIT approaching target levels (Fig. 2). areas outside the Hex River Valley, namely De Wet A number of factors were responsible for the and Brandwag. poor production, the most significant being This increasing population trend and fruit infes- problems with equipment and raw material, and tation after sterile releases, against expectation, is also the genetic stability of the GSS under the lo- ascribed to i) fewer than the required five million cal rearing conditions. In January and February (spring to autumn) and one million (winter) sterile 2000, a rapid decline in production was ulti- Medflies per week being released, especially from mately ascribed to contamination of bran used in October 1999 to May 2001 (Fig. 3), ii) too low a the larval diet with an insecticide, probably target (one million/week) being set for winter re- chlorpyriphos. A change of bran supplier solved leases,and iii) inadequate host plant management this problem. The genetic recombination in the in the target area. From June 2001 to December various GSSs between May 2000 and October 2002, 2002 the numbers of sterile flies released were and the subsequent colony replacements, also very close to the set targets (Fig. 3), and yet the reduced production to zero during these periods. numbers wild flies in 2002 reached an all-time This seriously compromised the delivery of sterile high (Fig. 1b). This suggests that the inadequate males to the Hex Valley. The frequent equipment host plant management programme in the Hex breakdowns up until about mid-2002, due largely Valley continued through 2002. Many growers to inadequate equipment being installed as a 138 Proceedings of the 6th International Fruit Fly Symposium

Fig. 3. Average weekly releases per month of sterile male Medflies in the Hex River Valley from project inception to the end of 2002, and the origin of these flies. result of budget restrictions, severely compro- regular audits of all procedures. By the end of mised the facility’s ability to produce the required December 2002 the positive effect of the QMS on levels of sterile males. production was evident, and for the first time the During these periods of inadequate production, production of sterile males reached and even sterile Medfly pupae were imported from the El exceeded requirement levels for any length of Pino Facility in Guatemala and the IAEA’s Seibers- time. dorf Laboratories in Austria in an attempt to meet the sterile release targets. Mating performance of reared vs wild fruit A number of other factors also compromised flies sterile male production: Owing to the prevailing weather conditions, no • Lack of initial expertise in rearing a genetic reliable data could be obtained from the VIENNA sexing strain of fruit fly. 7-97 flies in the cages placed outside the Infruitec • Shortage of space in the facility.Cramped condi- facility. However, results were obtained from the tions negatively affected air movement in the two cages inside breeding rooms at Infruitec, and egging rooms and therefore egg collection, as from the greenhouse in Seibersdorf. well as causing uneven temperature distribution Results showed a relative sterility index of in critical larval rearing rooms. 0.299, indicating that approximately 30% (out of a • Periodic shortages of adequately trained labour. possible 50%) of the matings of VIENNA 7-97 • Inadequate supervision of labour. males were with wild females. This is within the • The inclusion of up to 30% females in the steril- expected range of any mass-reared strain of ized flies sent to the Hex Valley. This was primar- Medfly. An isolation index of 0.259 was obtained, ily due to the absence of, or an ineffectual, Filter indicating a slight tendency towards homologous Rearing System. pairing between VIENNA 7-97 males and wild In mid-2002 a Quality Management System females, but no evidence of sexual isolation. (QMS) was developed and introduced in the rear- These results confirm that the VIENNA 7-97 tsl ing facility. This system comprised a comprehen- GSS is sexually compatible with the wild South sive set of Instructions and Procedures for each African Medfly population (Cayol 1998). step in the rearing, sterilization and delivery pro- cesses, together with a set of Specifications for Sterile fruit fly releases all consumable items. The QMS included non- The numbers of sterile males released per week conformance reporting and corrective actions,and over the Hex Valley between October 1999 and Barnes et al.: South Africa’s fruit fly SIT programme 139

December 2002 are shown in Fig. 3. The target an accidental release of fertile females from the level of five million (spring to autumn) and one rearing facility as a cause for the high infestation million (winter) sterile males per week was seldom rate in the Hex Valley can be excluded. achieved during the first 20 months up to May Results from the egg hatch test,sterility determi- 2001, despite supplementary imports of sterile nation and cage test with irradiated females pupae from Guatemala. During the following 19 showed no indication that females were fertile. months from June 2001 to December 2002 the Dosimetry in the irradiator was determined to be target production levels were more frequently correct, and no irregular irradiation procedures achieved, though there was still a heavy reliance were detected during the irradiation procedure on imported sterile pupae. Nevertheless, the audit. numbers of sterile flies released during this period Taking all the above evidence into consideration were very close to the set targets, and on a few it was therefore concluded that the Medfly infesta- occasions exceeding them (Fig. 3). tion in the Hex Valley in 2001/2002 did not arise Since the main objective of the Hex Valley pilot from fertile females from the rearing facility. The project had changed from eradication to cost- most probable source of infestation was consid- effective suppression of Medfly, the need for ered to be from wild fruit flies breeding on treating the two areas outside the Hex River Valley unmanagedalternatefruitflyhostplantsintheHex (the De Wet buffer area and Brandwag,comprising Valley. This situation was exacerbated by the fact approximately 4000 ha) with sterile flies had that the number of sterile males released per week diminished. As a result it was proposed by the was below the target level.The SIT team in the Hex ARC Infruitec-Nietvoorbij pilot project manage- Valley was advised to embark on an aggressive ment team that the sterile flies destined for these host plant management campaign, including the two areas would be better used if they were rather removal of unwanted fruit trees and other host diverted to the Hex River Valley itself, especially plants that could be dispensed with, fruit strip- in the light of sub-optimal sterile fly production ping, aggressive baiting of host plants which could and the host plant problem in the Hex Valley. This not be removed, and sound orchard and vineyard proposal was rejected by the Hex Valley SIT team sanitation throughout the SIT area. on the basis of SIT expectations that had been created amongst the growers in the De Wet and Success indicators in the Hex Valley Brandwag areas (W. Botes, pers. comm.). Despite the many problems experienced on all fronts in the Hex Valley project, it was widely Infestation outbreak in 2001/2002 agreed that the project had achieved a signifi- Mitochondrial DNA analysis. The GSS of Medfly cant degree of success and that the objective of used in the Infruitec-Nietvoorbij rearing facility cost-effective Medfly control had been realized. contain two types of genetic fingerprint (and only The following success indicators illustrate this: these fingerprints) – either the mitochondrial DNA Wild fly population levels. In the three years be- (mtDNA) haplotype AAAA or AAAB. These finger- fore the release of sterile flies, the mean popula- prints are a constant feature of this GSS, and do tion levels ranged from 0.9 to 1.0 FTD. In the not change over time or even during genetic three years following the release of sterile flies, breakdown. They are transmitted to the offspring mean FTDs ranged from 0.1 to 0.4 (Table 1). only through the females. Therefore, all male and Cost savings. The cost of controlling fruit flies in female Medflies released in the Hex Valley project the Hex Valley decreased from US$500 000 per area, as well as any potential offspring from un- year to approximately US$200 000 per year (W. sterilized females, must carry either of these two Botes, pers. comm.), a cost saving of some 67%. fingerprints. Reduction in export rejections. Following the re- A total of 137 pupae was recovered from infested lease of sterile Medflies, rejections due to fruit grapes collected from three different locations in flies of cartons of export table grapes destined for the Hex Valley area. In the IAEA’s Entomology Unit the U.S.A. were reduced by up to 50% (W. Botes, in Seibersdorf, 88 adults emerged from these pers. comm.). pupae and were subjected to mtDNA analysis. Reduction in pesticide use. Pesticide usage for None of the analysed flies showed the AAAA or the fruit fly control was reduced from routine applica- AAAB genetic fingerprints present in the GSS in the tions of 2–3 full-cover sprays and 7–15 bait sprays Infruitec rearing facility. The released flies clearly applied to all vineyards, to bait sprays applied differed from the field samples and, therefore, only to problem host plants. No routine fruit fly 140 Proceedings of the 6th International Fruit Fly Symposium sprays are applied to vineyards. the Western Cape is being focussed on a number of Integrated pest management benefits. Grapevine areas where Medfly predominates. mealybug (Planococcus ficus) and pear leafroller (Epichoristides acerbella) are key pests on table CONCLUSION grapes, and each has a complex of natural ene- Many fruit production areas in the Western Cape mies. The reduction in the use of fruit fly pesti- are suitable for the use of SIT for fruit fly suppres- cides on table grapes affords significant benefits sion and, under certain circumstances, eradication. for the integrated management of these pests, The Hex Valley SIT pilot project, conducted over although these benefits are difficult to quantify. 10 000 ha of predominantly table grapes, showed that SIT afforded cost-effective suppression of The future of SIT in South Africa Medfly, resulting in significant reductions in pesti- There is a growing understanding in the fruit cide usage and export carton rejections, and pro- industry of the benefits of an SIT programme for viding significant integrated pest management fruit fly, and that in the long term the industry benefits. needs SIT to remain economically viable in a com- However, the pilot project also highlighted a petitive international market. However, a lack of number of other facts: the rearing facility needs adequate funding remains the overriding con- adequate space and high-specification, well- straint. In the absence of significant government maintained equipment, with highly trained and involvement it is evident that to maintain an dedicated staff; Quality Management Systems SIT programme in South Africa,SIT should be com- for the rearing facility and field operations are mercialized. A cost–benefit study conducted on essential; the proper management of alternate the economic viability of a commercialized SIT fruit fly host plants in the target area is crucial to programme shows a potential demand for the success of an SIT programme; management between 69 and 76 million sterile fruit flies per and funding of the SIT programme should ideally week for the fruit industries of South Africa not be decentralized or fragmented between (Badenhorst 2001). different groups; an SIT programme is a manage- Negotiations for local and foreign investment in a ment and cost-intensive technology which ideally commercial enterprise have started. The initial needs to be wholly or largely administered by a goals are to prepare other fruit production areas single agent such as government. for SIT, and to construct a modular 50–100 million SIT is increasingly regarded as an indispens- sterile fly per week facility, which would provide able component of the export-orientated fruit improved economies of scale over the existing industry in South Africa. In the absence of signifi- pilot facility, and in which production could be cant government involvement in SIT in South scaled up in stages as demand from an expanding Africa, commercialization of the SIT programme is SIT programme increases. The potential to export likely be the best route to the sustainable and sterile Medflies to other SIT programmes should long-term use of SIT. also be investigated. The second species of fruit fly occurring in some REFERENCES areas of the Western Cape, the Natal fruit fly, has ANNECKE, D.P. & MORAN, V.C. 1982. 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