Up to date tsetse control or tsetse eradication programmes have been recorded from 18 African countries, viz. Botswana, Central African Empire, Ivory Coast, Kenya, Malawi, Mali, Mozambique, Niger, Nigeria, Republic of Cameroon, Republic of Chad, Rhodesia, Rwanda, South Africa, Tanzania, Uganda, Upper Volta and Zambia (see Fig. 2.1.).
In general chemical control or eradication is achieved by applying, as selectively as possible, a relatively persistent deposit of an insecticide to the potential resting sites of the flies. So far in the majority of the operations either DDT, dieldrin or endosulfan have been used. Very probably the most discriminative method of application is the groundspray procedure where the pesticide is applied either directly to distinct parts of the vegetation, e.g. tree-trunks up to a certain height, underside of inclined branches, by means of knapsack spraying equipment. For economic reasons and because of the extensiveness of certain flybelts, aerial applications have become widely used during the last decade. Also in aerial spraying many efforts have been made to transfer the insecticide as efficiently as possible to the target organism. The latter may be achieved by a proper selection of type of aircraft, atomizers and spray formulation. In this connection extensive use is made of the vast amount of knowledge which is available at present about the ecology of the tsetsefly species concerned.
Below an account will be given of the chemical control and eradication procedures which have been or are being applied in the various countries listed above. Special attention will be given also to the type of habitat treated and the success obtained. It must be mentioned that the brief summaries only cover the main activities and therefore do not necessarily refer to all the reports and publications which might be available.
In the literature before 1972 only little information is available on tsetse control in Botswana. Graham (1964) refers to dieldrin (Unimog applications of Dieldrex) applications against G. morsitans in an area near Maun, but provides no details on fly distribution, application rates etc. In 1972 eradication operations were started in the Okavango Delta against G. morsitans morsitans Westw. The eradication method consisted of fixed-wing aerial ULV (ultra low volume) aerosol (non persistent) applications of endosulfan (Kendrick and Alsop, 1974). After the experimental trials proved to be successful in 1973, large scale operations were started in 1974. These were continued in 1975 and 1976 (Kendrick, personal communication, 1976).
Annually some 2 000 – 3 000 km2 are treated. It is anticipated that the Okavango swamp will be reclaimed from tsetse within a few years.
|Formulation||:||200 g/l from 350 g/l e.c. (emulsifiable concentrate) (Hoechst A.G.) diluted in Shellsol AB.|
|Dose Rate||:||3.0 1/km2 (0.6 kg a.i. (active ingredient) /km2)|
|Aircraft||:||Piper Pawnee (trials 1973) Piper Aztec (trials 1973; 1974–76)|
|Atomiser||:||Micronair Rotary Atomiser AU 3000|
|VMD (volume median diameter) of spray)||:||24–41 μm|
|Habitat||:||Swamp, characterised by large Papyrus (Cyperus papyrus) communities.|
Central African Empire
Tsetse control operations with dieldrin groundspray started in 1960 in the Baboua Sous-Préfecture at the River Nie and its tributaries. As the results were satisfying is was decided to treat a more important area, viz. the Valley of the river Topia. The actions were directed against G. fuscipes fuscipes Newst. The whole vegetation of the valley was sprayed. Preliminary results were encouraging. (Yvore et al., 1962).
|Formulation||:||2% a.i. solution of Dieldrex 20%|
|Equipment||:||pressure retaining knapsack-sprayers.|
Only one record has appeared about tsetse control viz. the eradication of G. palpalis gambiensis Vand. in the gallery forests near Abengourou and Daloa. DDT and dieldrin were deposited to prevent the spead of human trypanosomiasis (Challier, 1971).
In this country tsetse control has been directed mainly to G. fuscipes and G. pallidipes, which are responsible for the transmission of human trypanosomiasis in the Nyanza Province. Some of the preliminary applications of dieldrin groundspray were reported by Thomson et al. (1960). Ever since spraying operations have been carried out both in Central and South Nyanza, whereby part of the shore-line of Lake Victoria and some of the valleys which were formerly heavily infested, were reclaimed from tsetse. In certain places bushclearing was applied to create barriers against re-invasion of reclaimed areas (e.g. Bertram, 1969). In the Lambwe Valley in South Nyanza dieldrin applications by means of fixed-wing aircraft and helicopters were made which gave reductions of 99% for periods up to several months of the local G. pallidipes population (e.g. Willett, 1972).
|Formulation||:||1.8% solution from Dieldrex 15 T (18.2% dieldrin emulsion) in water|
|Equipment||:||Kiekens Dekker portable mist blowers|
|Dose rate||:||4 applications of a 1.8% dieldrin solution (1960), 2 applications of 2,5–5% dieldrin solutions (1967–1970)|
|Aerial spray||:||no details published|
|Habitat||:||relatively moist Savanna Woodland|
There is a record from Steele (1956), in which the use of γBHC against G. brévipalpis Newst. is reported. A 4% solution of γBHC in diesel oil is applied in six applications with intervals of 10 days, by means of a ‘Swingfog’ spraying apparatus.
The need for tsetse control has only occurred in the southern most part of the country, alongside the river Niger and its tributaties. In 1962, riverine forests around Bamako were treated with single applications of residual insecticide, to eradicate G. palpalis gambiensis Vand., h.l. the vector of human trypanosomiasis. To prevent reinvasion, chemical barriers were laid with 4% Dieldrin solutions. The campaign was successfully continued from 1963–68. Approximately 400 km of fringing forests were kept under control with either DDT or dieldrin (Challier, 1962 and 1971).
|Formulation||:||3% solutions in water of dieldrin 20% e.c.|
DDT: no details recorded
The only record of tsetse control operations in Mozambique, which has come to our knowledge, was the eradication of G. morsitans in the Govuro district, south and near the mouth of the Suave River (Silva and Silva, 1960). From 1949 to 1956 an area of approximately 1,200 square miles (3.008 km2) has been reclaimed by means of game eradication, settlement of local people, dipping of cattle with DDT and γBHC, controlled grass fires and deflying of the traffic. Habitat: an undifferentiated, relatively dry Savanna woodland (Sudan type). Considerable areas of Mozambique near the Rhodesian border were treated by knapsack spraying in the early 1970s but this operation was recently discontinued (N.J. Alsop. pers. communication).
Tsetse flies in Niger mainly occur in the gallery forests and the I. Doka woodlands which border the river Niger and its western tributaties, south of Say. The species concerned are G. tachinoides Westw. and G. morsitans submorsitans Newst. In the 1967/68 dry season a groundspray operation was started with several residual insecticides. At the confluence of the river Tapoa and river Niger a cleared barrier was made, to prevent reinvasion of flies from the south in reclaimed areas. Helicopter spraying of approximately 1,200 ha of riverine vegetation was carried out successfully in the 1969/70 dry season, just south of Say (Spielberger, 1971). As major improvements of the helicopter spraying technique were achieved by Spielberger and Abdurrahim in Nigeria (1971), it was decided to spray the remaining tsetse habitats of Niger (approximately 42,000 ha) with endosulfan, by means of aerial helicopter applications. Only an isolated focus in the Dallol Maiori will be treated with groundspray techniques. Spraying should have started in December 1975 but was postponed to 1977.
|Insecticide||:||DDT, γ-BHC and dieldrin mixture|
|Formulation||:||Multanin liquide 3 (DDT 23%, γBHC 9%, diel- drin 9%), 3% watery solution. Multanin (DDT dissolved in Kerosene) pur DDT powder|
|Equipment||:||Solo knapsack sprayer (3% Multanin liq. 3) Swingfog back sprayer (Multanin) Schupze-Eckel duster, mounted on a vehicle (DDT powder)|
|Insecticide||:||1969/70: DDT, γBHC and dieldrin mixture for- mulated as Multanin liquide 3, 12.5% watery solution; 5.0 l/ha; two applications with three-week intervals|
future: Endosulfan 25% ULV (HOE 2958); 6 1/ha (1.5 kg a.i./ha); single application
|Aircraft||:||Bell 47 G4|
|Atomiser||:||electrically driven twin discs|
|Droplet size||:||100–300 μm|
Tsetse control and eradication in Nigeria with chemical means was undertaken since 1954. Different methods were used depending on the vegetation zone and the species of fly present. In the treated areas, three main species of tsetse occur, viz. G. morsitans submorsitans, Newst., G. tachinoides Westw. and G. palpalis palpalis Rob.-Des. Two major vegetation zones had to be considered, the Northern Guinea and the Sudan, which are distinct in some parts and overlap in the Sub-Sudan zone. Until 1970, only groundspray methods with residual insecticides have been used. The various spraying techniques which were developed, are described in detail by Aitchison and Glover (1970).
During the years 1954–70 a total of 10,644 square miles (27,570 km2) of tsetse infested country in north-eastern Nigeria has been reclaimed, making 26,540 square miles (68,740 km2) safe for grazing of cattle (Davies, 1964 and 1971). Insecticide barriers have been successfull in protecting sprayed areas from fly reinvestation between spraying seasons. It is reported that cleared barriers have, so far, succeeded in providing permanent protection to completed projects. Periodic checks indicate that all the country reclaimed is free of fly.
In 1970 insecticide spraying by means of helicopter was introduced when a small area was treated with 4% dieldrin with success against G. morsitans. Since then (1971) helicopter applications of both dieldrin and endosulfan have become a regular means of tsetse eradication in Nigeria, together with groundspraying of DDT and dieldrin.
In the period 1970–75 another 44,172 square miles (117,711 km2) have been covered by the Nigerian Tsetse and Trypanosomiasis Division, which makes a total of 71,712 square miles (186,451 km2) made safe for grazing since 1956 (Annual Report of TTD, 1973–75). Following a recommendation of the 1975–80 Development Plan of Nigeria, an experiment with fixed-wing aircraft in tsetse control was started in March 1976. An area of approximately 2,000 km2 was chosen in the Southern Guinea Savanna zone, viz. the Doma Forest Reserve. Methods and materials were used as known from Botswana. A difference was that in Nigeria the dose rate of endosulfan was 14 g a.i./ha instead of 6 g a.i./ha. It was reported that, so far, no complete success has been achieved (reductions of 85% were recorded, N.J. Alsop, pers. communication), but it is anticipated that in the years 1976/77 and 1978/79 the method will be tried out again on an experimental scale. In the forthcoming years tsetse control in Nigeria will again cover large areas. Chemical control by groundspray and aerial spray (helicopter and fixed-wing) will be continued whilst biological control methods with sterile-male techniques will be introduced (Na'isa, 1974).
|Insecticide||:||DDT (drier areas) and dieldrin (wetter areas)|
|Formulation||:||2,5–5% DDT WP (70% DDT)|
2% dieldrin (from Dieldrex 15 T) in water
|Equipment||:||knapsack, motorized mistblower|
|Habitat||:||Sudan and Northern Guinea Savanna|
|Formulation||180 g/l in Shellsol R/Dutrex (Ensodil EF 4220)||250 g/l (Thiodan 25% ULV HOE 2958)||200 g/l (Thiodan 20% e.c.)||250 g/l (Thiodan 25% ULV HOE 2958)|
|Dose rate||800–900 g a.i./ha one application only 10% of habitat||1000 g a.i./ha one application only 10% of habitat||14 g a.i./ha, five applications with 12-day intervals blanket spraying||15 g a.i./ha, 5 applications with 12-day intervals blanket spraying (in this case aerosol) drift using 225 m lane separations|
|Aircraft||Bell helicopter||47 G - 4 A||Piper Aztec PA|
electrically driven twin discs
|VMD of spray||150 μm||150 μm||27 – 30 μm (e.c.)||32 – 37 μm (ULV)|
|Habitat||Sudan and Northern Guinea|
Republic of Cameroon
Results of the use of dieldrin groundspray in the Chari River basin are discussed under: Republic of Chad
Recently a tsetse control programme for the years 1976–78 was launched in which it is aimed to reclaim 8,200 km2 of the western Adamaoua Highlands from tsetse by means of ULV pesticide applications. Pesticides will be sprayed by helicopter to the dry season concentration areas of G. morsitans and G. palpalis, in single application, viz. the riverine fringing forests and comparable habitats. This means that 8–15% of the total area will actually be sprayed. Based on previous experiences in Nigeria, it was decided that approximately two thirds of the tsetse habitats will be sprayed with dieldrin and one third with endosulfan (the drier parts of the habitat).
Spraying will start in December 1976 with one helicopter, whilst in the 1977/78 and 1978/79 dry seasons two helicopters will be used. The northern boundary of the project area will be cleared from bush, in order to prevent tsetse infestation from the northern lowlands (G.T.Z. personal information).
see Nigeria: Technical details of aerial helicopter applications.
Republic of Chad
The results of a small-scale control campaign with dieldrin in the Logone and Chari river systems of Chad and North Cameroon are discussed by Mouchet (1962). Suggestions have been made for large-scale operations of chemical spraying. However, according to Cuisance and Itard (1975) in 1972/73 the same river basins have been used for experiments with sterile males of G. tachinoides Westw.
Technical details (chemical spraying only):
|Formulation:||1.8% watery solution of dieldrin 50% WP single application, discriminative spraying.|
Bushclearing and game eradication have been widely adopted in tsetse control in this country (Lovemore, 1961). Residual insecticides are applied since 1959. In that year the vegetation of the Lundi River system was sprayed with a 3.6% dieldrin solution. The extension of the south-eastern flybelt has been stopped with success after one application only (Farrell, 1960). Thereafter dieldrin and DDT have been used widely for tsetsecontrol, applied either with aircraft (Cockbill et al., 1963) or groundspray equipment (Vale, 1968; Casewell, 1969). In 1966 it was decided to spray part of the 1,900 square miles (4,919 km2) flybelt of Inyanga North and south-eastern Mtoko as bushclearing did not arrest the advance of the tsetse flies. These operations were continued in 1967. However the use of dieldrin and DDT applied either alone or in combination, did not result in complete eradication of the fly population of G. morsitans (Casewell, 1969). In the 1968-spraying operations only 5% DDT WP suspensions were used because of lower insecticide costs (Value, 1968). Following the successfull ULV aerial applications of endosulfan in Zambia (Park et al., 1973) and Botswana (Kendrick and Alsop, 1974), 494 km2 of bush infested with G. morsitans morsitans Westw. and G. Pallidipes Aust. were sprayed in 1974/75 in Rhodesia with methods as developed in the above-mentioned countries (Chapman, 1976). Around the endosulfan area a groundspray barrier was made with a suspension of 5% DDT WP. Although a marked decrease of the fly population was observed, a total eradication has not been achieved. The reoccurrence of flies is said to be caused by reinvasion of vehicle-carried flies. Experiments with biological control have been carried out in the Lake Kariba region. The first results were reported to be promising (Dean et al., 1969).
|Formulation:||3.1 and 3.6% dieldrin emulsion in water from Dieldrex 15T (containing 18.6% dieldrin e.c.) 5% solution in water of DDT 75% WP|
|Equipment:||motorised, shoulder mounted mist-blowers.|
Aerial spray: (1974/75 operations only)
|Formulation:||Endosulfan 20% e.c. in Shellsol AB and|
Endosulfan 25% e.c. in Shellsol AB
|Dose rate:||6 or 7 1/km2 (14 g a.i./ha)|
5 applications with intervals of 12 to 18 days.
|Aircraft:||Piper Aztec (1974)|
Piper Pawnee (1975)
|Atomiser:||Micronair AU 3000|
|Habitat:||Miombo woodland (comparable to Guinea Savanna of W. Africa)|
In this country tsetse control by chemical means took place for the first time in the Bugesera region (S.E. Rwanda) in 1960. From August 1976 till March 1961 an area of 19.000 ha (3,568 ha tsetse biotope) was reclaimed by discriminative aerial spraying of dieldrin (Buyckx, 1961).
As Telodrin is 2.5 times as toxic to the Rwanda species of tsetse (G. morsitans centralis Machado) than dieldrin costs of the campaign were supposed to be reduced by replacing dieldrin by Telodrin. In the season 1961/62 trials were made with both insecticides in two different areas. Tsetse elimination was reached over 43,000 ha (5,321 ha biotope).
Finally, in 1963/64 dieldrin was applied during the first half of the campaign and later replaced by Telodrin within the same area. Thus 50,000 ha of flybelt (13,240 ha biotope) were reclaimed of tsetse eventually (Buyckx, 1964). In the first season series of 8 successive applications with 28 day intervals were usual, but the latter were changed to 24 day intervals in the 61/62 and 63/64 campaigns due to shorter duration of pupal life.
|Insecticide:||Dieldrin FL 20% or|
Telodrin 15% EC
|Dose rate:||Dieldrin 44 g a.i./ha discriminative 8 applications|
Telodrin 16.5 g a.i./ha discriminative 8 applications
|Formulation:||1 l dieldrin FL 20% dissolved in 6.5 l illuminating Kerosene|
Telodrin 15% e.c. dissolved to 1.5% with one part
Diesoline and eight parts illuminating Kerosene, later changed to one part Telodrin 10% with six parts illuminating Kerosene
|Atomiser:||Micronair A 100|
|Habitat:||Relatively moist Savanna Woodland|
An elaborate description of the use of organichlorine insecticides in tsetse control operations is given by DuToit (1954) extensively. From 1945 to 1953 aerial spraying of γ-BHC in smoke form (described as Thermal exhaust aerosol method) against G. brevipalpis and G. pallidipes took place in Zululand, at that time the only tsetse infested area in South Africa. As this happened in the early phase of aerial spraying in tsetse control, trials were made with helicopter and fixed-wing aircraft. Eventually sprayings with a Piper Super-Cub gave the best results.
Areas inaccessible to fixed-wing aircraft were initially treated with groundspray methods, whilst ultimately these were replaced by aerial spraying with helicopter. The groundspray teams were applying 5% DDT in dust from.
Outside the tsetse habitats, cattle were treated with a solution consisting of 0.16% As2O3 and 0.1% of DDT in water by means of dipping once weekly. This was only done in those areas where cattle outnumbered the natural game populations. To prevent tsetse from extending its territory, a tsetse border was established by bush clearing an area of approximately 2 miles wide and 94 miles in total length. No further literature about anti-tsetse operations in South Africa has come to our knowledge.
|Formulation:||5% DDT dust powder|
|Dose rate:||7,9 kg/ha|
|Aircraft and dose rate:||- twin-engined Anson 100 g a.i./ha, emitted through the exhaust stacks by gravity; 8 applications|
- single-engined Piper Cruiser 40 g a.i./ha, emitted through the exhaust stacks by fuelline pump; 8 applications
- Sikorsky S 51 helicopter 80 g a.i./ha, emitted through the single exhaust stack by gravity; 8 applications.
|Habitat:||Dry woodland savanna|
Apart from South Africa, early research on the use of aircraft in tsetse control has been reported from Tanzania (Yeo and Thompson, 1954). Initially the aircraft were equipped with gravity-fed exhaust injection systems which used the hot gases from the aircraft exhaust to automise the insecticide formulation. Extensive research with different types of aircraft have led to the development of the Micronair Rotary Atomisers, as are now being used in Botswana, Nigeria and Rhodesia (Lee, 1969; Lee et al., 1969). At the Tropical Pesticide Research Institute (TPRI) in Arusha many different pesticides have been tested experimentally for tsetse control, mostly in small pilot projects (Burnett, 1962 a,b; Burnett et al., 1964; Hocking et al., 1966; Irving et al., 1969; Irving and Beesley, 1969; Tarimo et al., 1971). However, according to our knowledge there has never been a large-scale programme of tsetse control with chemical means in Tanzania. Although in the early fifties game eradication was applied on a large scale in Shinyanga-North, it is no longer considered an important method of tsetse control anymore (Potts, 1952).
A total area of 39,583 km2 has been successfully reclaimed from tsetse infestation between 1947 and 1973. Various methods have been used: bushclearing was carried out to establish barrier-zones, whilst game-eradication was applied in two schemes. Today the latter is not considered to be a significant method anymore, and is only used occasionally. The eradication method most widely used is the discriminative spraying of 3% dieldrin emulsion in single applications. Only groundspraying methods have been used so far. As human trypanosomiasis is no longer a serious problem in Uganda, control methods are mainly directed to the elimination of trypanosomiasis from cattle. An area of approximately 48,000 km2 remains still under tsetse occupation (Wooff, 1969; Kanwagye, 1975).
Endosulfan (only 351 km2 in 1971)
|Formulation:||3% dieldrin from Dieldrex 15T 18% e.c.|
2,5% endosulfan from Thiodan 35% e.c.
|Dose rate:||Dieldrin: 90–180 g a.i./ha|
Endosulfan: no detailed information
|Equipment:||leo-colibri CP 201 and CP148 pneumatic knapsack sprayers and CP40 knapsack mistblowers|
N.B. Trials to control tree regeneration in tsetse barrier zones with Tordon 101 arboricide are being investigated. Results are reported to be encouraging (Oliaka, 1975).
In the dry season of 1962/63 (Jan-April 1963) trials with γ-BHC fogging have been carried out near the village Sénoufo de Kankalaba, Western Upper Volta, to exterminate G. palpalis gambiensis Vand. Only riverine forests were sprayed six times (solutions of 3% γ BHC in diesel oil). Intervals between applications amounted to 20 days but were reduced to 15 days because of the shorter ovarian cycle in the dry season (Challier, 1964).
The author concludes that the fly population has markedly been reduced but not fully eradicated as two months after the last application the fly density was 2% of that of the pre-spray figures. In August 1962 a barrier zone with a length of 1500 metres was made downstreams the experimental area by means of DDT (3% DDT wp. sprayed daily for three weeks)
|Insecticide:||γBHC (from ‘Procidacri 100’)|
|Habitat:||Northern Guinea Savanna|
The Zambian Veterinary and Tsetse Control Services have extensively used bush-clearing as a means of tsetse control in various parts of the country. As for chemical control: groundspraying has been carried out with vehicle-mounted mechanical equipment and with knapsack sprayers. It is intended to intensify the last method. (R.S. Hacizenge, personal communication, 1976.)
Large scale aerial ULV application of endosulfan takes place in Zambia since 1968. G. morsitans morsitans Westw. is the target organism. In 1968 an area of 1,600 km2 was sprayed from aircraft with coarse aerosol of endosulfan. Postspray flyrounds showed that tsetse eradication was apparently achieved except near an unsatisfactory isolation barrier (Park, Gledhill, Alsop and Lee, 1972). In 1970, 1971 and 1972 areas of 1,500 km2 yearly were sprayed in the same manner (Kendrick and Alsop, 1974). It is reported that future aerial spraying will be carried out with the same techniques as is now being used in Botswana (Hadaway, personal communication).
|Insecticide:||DDT 38g/1 from DDT 75% W.P. Dieldrin 18 g/1 from Dieldrex 15T 20% e.c. (added to the DDT solution during the last 3 months of spraying season)|
|Equipment:||Unimog (Mercedez Benz) tractors carrying 750 l spray tanks connected with pump and atomizers|
|Insecticide:||Endosulfan 35% e.c.|
|Formulation:||200 g/1 in SHELLSOL AB|
|Dose rate:||15 g/ha, 4–5 applications|
|Aircraft:||1968: Cessna 180 and Piper Pawnee|
1970–1972: Beechcraft Baron
|Droplet size:||20–100 microm. vmd 20 microm. '68|
vmd 70 microm. '70
|Habitat:||dry deciduous forest and savanna on the Kalchari Sands|
Only a few pesticides have been used succesfully so far. It concerns especially those pesticides which form relatively persistent deposits on the leaves and branches, e.g. dieldrin, DDT and endosulfan. Trials with ultra-low volume low-dose rate applications of endosulfan (knock-down method) appeared to be successful in Botswana.
In the former periods most control operations were carried out by ground spray units. At present there is a strong tendency to replace groundspraying, at least partly, by aerial spraying. In connection to the latter both helicopters and fixed-wing aircraft are being used. One of the advantages of aerial spraying is that larger areas can be treated during one season than is possible by groundspraying.
Most operations carried out sofar were directed to dry savannas (e.g. the Sudan savanna in West Africa and the Miombo woodland in East and South-east Africa (see Fig. 2). It is to be expected that as soon as most of the dry areas have been reclaimed in certain countries the spraying activities will be extended to the moister savanna areas (e.g. the Guinea savanna zone in West and North-central Africa). In this connection it should also be remarked that in most areas one cannot distinguish easily between dry and moist savannas because most types of habitat occur together e.g. Doka woodland with G. morsitans submorsitans and riverine forest with G. tachinoides and G. palpalis).
Fig. 2.1. Political Map of Africa
Figure 2.2. Map showing relationship between tsetse distribution and moist and dry savanna areas