Pesticide Residues in Coastal Tropical Ecosystems: Distribution, fate and effects - Chapter 3 pps

Pesticide use in Zimbabwe 21Chapter 3 Pesticide use in Zimbabwe Impact on Lake Kariba, a tropical freshwater ecosystem Mark F. Zaranyika INTRODUCTION Zimbabwe is situated within the African tropics (Lat. 15 ° to 22 ° S and Long. 26 ° to 34 ° E), occupies an area of 390,580 km 2 and has a population of about 11 M. The Zambezi River forms the boundary with Zambia to the north, and the Limpopo River forms the boundary with South Africa to the south. The eastern highlands that form the rim of the African Plateau (before descent to the Mozambique Coastal Plain), constitute the greater part of the border with Mozambique. In the west, the boundary with Botswana follows the eastern limit of the Kalahari Desert. Zimbabwe is a landlocked country. Its GDP for 1990 and 1994 was Z$14,643 M and Z$39,775 M, respectively. The agriculture sector contributes about 13 percent of GDP, while the export of agricultural products contributes 50 percent of the country’s total annual export earnings (Central Statistical Office, 1990). The use of pesticides plays a major role in maintaining these high levels of agri- cultural production. As in most tropical countries in Africa, pesticides are also extensively used in the public health arena to control diseases such as malaria (a nonhemorrhagic fever caused by protozoans of the genus Plasmodium Marchiafava and Celli and vectored by Anopheles Meigen spp. (Diptera: Culicidae) mosquitoes), African trypanosomiasis (African sleeping sickness, a nonhemorrhagic fever caused by protozoans of the genus Trypanosoma Gruby and vectored by tsetse flies, Glossina spp. (Diptera: Glossinidae), and typhoid (a bacterial illness caused by Salmonella typhi spread in contaminated food and water). Of late, there has been concern about the possible effects the use of pesticides has on tropical environments, including tropical marine and fresh water ecosystems. The effect of pesticides on the environment depends on several factors such as climate, in particular tempera- ture and rainfall; soil type and the nature of the vegetative cover; biotic activity; light intensity; agricultural practices; and mode of introduction of the pesticide into a particular environmental compartment. These factors determine the persistence of a pesticide in a specific environment, and in this respect, OC pesticides as a group have been found to be the most persistent. OC pesticides have been used extensively since the early 1960s to control the tsetse fly and malaria vectors in southern east-central Africa, i.e. Zimbabwe, © 2003 Milton D. Taylor, Stephen J. Klaine, Fernando P. Carvalho, Damia Barcelo and Jan Everaarts 22 Mark F. Zaranyika Mozambique, and South Africa (Ford, 1971). DDT has been used for this purpose since 1962, while dieldrin was used during the period 1962 to 1967 (Ford, 1971; Mpofu, 1987; Whitwell et al., 1974). Endosulfan and BHC are currently used, especially for aerial spraying (Chapman, 1976). DDT was used in Zimbabwe for more than four and a half decades, from 1946 to 1983 (Chikuni, 1996). In addition to its use to control the tsetse fly and malaria vectors, DDT was used extensively for the control of agricultural pests such as the maize stalkborer Busseola fusca Fuller (Lepidoptera: Noctuidae), cotton cutworm Agrotis spp. (Lepidoptera: Noctuidae), and cotton bollworm Helicoverpa armigera Habner (Lepidoptera: Noctuidae). DDT was used in agriculture until 1983 when this use was banned. However, it is still registered with the Ministry of Health’s Hazardous Substances Control Board as a ‘hazardous substance class 1’, i.e. a chemical that can endanger humans and domestic and wild animals, and its procurement and use are restricted to cover tsetse and mosquito control only (Chikuni, 1996). Other OC pesticides registered for use in agriculture in Zimbabwe include dieldrin, endosulfan, BHC, aldrin, chlordane, dicofol, and chlorthal- dimethyl. This chapter discusses the use of pesticides in Zimbabwe and how this has impacted on Lake Kariba, a tropical freshwater ecosystem. Lake Kariba is one of the world’s largest man-made lakes. It was constructed in the mid-1950s, started to fill in 1958, and reached full capacity in 1963. Situated in south-central Africa (between Lat. 16 ° 30' to 18 ° S, and Long. 27 ° to 39 ° E), the lake is politically shared by Zambia and Zimbabwe, with the international border bisecting the lake longitudinally (Figure 3.1). Its physical dimensions are given in Table 3.1. Geographically Lake Kariba is part of the middle Zambezi region and lies in a rift valley (the Gwembe Valley), overlooked on both sides by steep escarpments. The mean maximum temperature is 30.4 ° C, while the minimum annual mean temperature is 18.2 ° C. Rainfall around the lake region is generally low; the annual mean for the period 1951 to 1986 was 734 mm (Leggett et al., 1991). Generally the wet season occurs in the months of December to March, with occasional storms Table 3.1 The physical dimensions of Lake Kariba, Zimbabwe at the normal operating water level (see Figure 3.1) a Water level (above sea level) 485 m Length 277 km Mean breadth 19.4 km Mean depth 29.18 m Maximum depth b 93 m Surface area 5364 km 2 Volume 156.5 km 3 Theoretical renewal time of the water mass 3 years approx. Notes: a Source Balon and Coche (1974). b Occasional deeper ‘holes’ not considered. © 2003 Milton D. Taylor, Stephen J. Klaine, Fernando P. Carvalho, Damia Barcelo and Jan Everaarts Pesticide use in Zimbabwe 23 in October, April, and May. There is no rainfall from June to September. Evidence of a pesticide residue build-up in Lake Kariba has been reported by several workers (Billings and Phelps, 1972; Whitwell et al., 1974; Greichus et al., 1978; Wessels et al., 1980). Thus, in 1980, Wessels et al. were prompted to warn that ‘in view of the extensive fishery development taking place on the lake, the problem of residues in human food may become a serious matter’. The background and extent of the problem are the subject of this chapter. IMPORTATION, MANUFACTURE, AND REGULATION OF PESTICIDES IN ZIMBABWE The use of pesticides in agriculture: importation and regulation of pesticides in Zimbabwe The use of pesticides in Zimbabwe is regulated in terms of the Pesticide Regulations of 1977, under the Fertilizer, Farm Feeds and Remedies Act (Chapter 111) of 1952 (Government of Zimbabwe, 1952) and the Hazardous Substances and Articles Act (Chapter 322) of 1972 (Government of Zimbabwe, 1972). The Fertilizer, Farm Feeds and Remedies Act (Chapter 111) is administered by the Ministry of Lands, Agriculture and Rural Resettlement. This act prohibits the sale or distribution of Figure 3.1 Lake Kariba with inflows from Zimbabwean rivers Source: Wessels et al. (1972). © 2003 Milton D. Taylor, Stephen J. Klaine, Fernando P. Carvalho, Damia Barcelo and Jan Everaarts 24 Mark F. Zaranyika pesticides unless they have been registered with the Plant Protection Research Institute. Registration is carried out under the Hazardous Substances and Articles Act (Chapter 322) which is administered by the Ministry of Health and Child Welfare. Before registration, pesticides are classified on the basis of their acute oral lethal dose (LD 50 ) and persistence after application. The classification (poison group) is indicated by a green, amber, red, or purple triangle on the label for LD 50 values of greater than 2,001, 501 to 2,000, 101 to 500, or 0.1 to 100 mg kg –1 , respectively. Pesticides can only be imported into the country after they have been registered. It is also a requirement that all imported pesticides be registered in the country of origin. The complete list of registered pesticide products in Zimbabwe is very long (approximately 600), but compared to the total number of pesticides available worldwide (>40,000), this number is small. Several companies are involved in the formulation and marketing of pesticides in Zimbabwe. The major formulators are (with the number of formulations registered by each company shown in brackets): Agricura (99), Zimbabwe Fertilizer Co. (ZFC) (71), Windmill (66), Bayer (62), Shell (48), Ciba-Geigy (34), Spray-quip (26), Hoechst (16), Omnichem (15), and Wellcome Environmental (17) (Mathuthu, 1993). There are several minor pesticide formulating companies including Rhone Poulenc (11), Technical Services (6), Fercochem. (4), Oxyco (4) and T.S.A. (2). Some formulations of Agricura and ZFC are made totally from local raw materials. The other companies, to a large extent, merely import the active ingredients from which they make their formulations. A list of pesticides commonly used for crop pests in Zimbabwe is given in Tables 3.2 and 3.3. The formulations commonly marketed in Zimbabwe were selected following a market survey, which involved visits to major outlets that sell pesticides, e.g. the Farmers Cooperation, Agricultural Buying and Veterinary Services, whole- sale centers, and supermarkets, in addition to interviews with farmers (Mathuthu, 1993). The pesticides listed in Tables 3.2 and 3.3 are those formulations that are most commonly used around the country. The tables show the brand name and a.i. of the pesticide, its poison group, and the chemical class of the compound. The poison group indicates the degree of toxicity of the pesticide and is indicated by the symbols P (Purple), R (Red), A (Amber), and G (Green), with P indicating the most toxic pesticides and G the least toxic. The Agricultural Chemicals Industry Association (ACIA) represents all manufacturers and distributors of agrochemical and animal health products in Zimbabwe. The ACIA is a member of the International Group of National Associa- tions of Agrochemical Manufacturers (GIFAP). Through GIFAP, the ACIA has endorsed the FAO’s code of conduct on the distribution and use of agrochemicals (Mbanga, 1996). © 2003 Milton D. Taylor, Stephen J. Klaine, Fernando P. Carvalho, Damia Barcelo and Jan Everaarts Pesticide use in Zimbabwe 25 Table 3.2 Pesticides used in Zimbabwe: grouped according to chemical classes of the compounds a Brand name Active Poison Type of ingredient group b compound Alfacron 50 W.P. azamethiphos 50% R OP Kaptasan F captan 31.35% + G OP fenitrothion 1% Steladon chlorfenvinphos 30% P OP Dursban 4E chlorpyrifos 40.8% R OP Fly Bait dichlorvos 0.5% A OP Diazinon DFF diazinon 86.88% P OP Diaz 30 diazinon 30% R OP Rogor C.E. dimethoate 36% R OP Dimethoate 40 E.C. dimethoate 40% R OP Disystem 5% granule disulfoton 5% P OP Altomix 7.75G disulfoton 7.5% + P OP cyproconazole 0.25% Lebaycide 50% fenthion 50% R OP Folithion 60 E.C. fenitrothion 55.49% R OP Kontakil fenitrothion 60% R OP Ant-Killer fenitrothion 17.5% A OP Anthio 33 E.C. formothion 33% R OP Fyfanon 1000 E.C. malathion 86% A OP Kilathion 100 E.C. malathion 83.5% A OP A.B.C. powder (dust) malathion and other G OP Damfin 2P methacrifos 2% G OP Kudzivirira Mbesa malathion 1 G OP Malathion 1% Dust malathion 1% G OP Malathion 5% Dust malathion 5% G OP Malathion 25% W.P. malathion 25% G OP Malathion 50% E.C. malathion 50% G OP Pythion 21 malathion 2.2% G OP Metasystox R 25% E.C. oxydemeton-methyl 25% R OP Wellcome grainguard pirimiphos-methyl 48.8% G OP Shumba 2% dust pirimiphos-methyl 2% G OP Bolstar 720 E.C. sulprofos 72% R OP Sprayquip stalkborer 2% granules trichlorfon 2.5% G OP Aldrin 40% W.P. aldrin 40% P OC Anti-Kil chlordane 30% A OC Razor chlorthal-dimethyl 36% G OC Dicofol 40 E.D. dicofol 40% A OC Kelthane dicofol 18.5% G OC Dieldrex 50 W.P. dieldrin 50% P OC Thionex 1% granules endosulfan 1% G OC Thiodan 1% granules endosulfan 1% G OC Thiodan 20 E.C. endosulfan 20% P OC Multi Benhex γ-BHC 12% + total R OC BHC 75% Gamatox house spray γ-BHC 5.0% A OC Bexadust (L) γ-BHC 0.6% G OC Agri seed dress 75% lindane 1% R OC Temik 15G aldicarb 15% P carbamate Carbaryl 85 S carbaryl 85% A carbamate Carbaryl 85 W.P. carbaryl 85% A carbamate Harakiri carbaryl 0.3% G carbamate continued… © 2003 Milton D. Taylor, Stephen J. Klaine, Fernando P. Carvalho, Damia Barcelo and Jan Everaarts 26 Mark F. Zaranyika Table 3.2 continued Brand name Active Poison Type of ingredient group b compound Cypam E.P.T.C. 77% G carbamate Baygon residual spray propoxur 2.0% + dichlorvos 0.5% G carbamate Decis 2.5 E.C. deltamethrin 2.5% R pyrethroid Agrithrin Super 5 E.C. esfenvalerate 5% R pyrethroid ICON 10 W.P. λ-cyhalothrin G pyrethroid Bymo insect killer pyrethrins 0.125% G pyrethrin Wellcome permethrin 25% G pyrethroid G-17 pyrethrins 2.25% G pyrethroid Dusting powder pyrethrins 0.20% G pyrethroid Garden insecticide concentrate pyrethrins 1.5% G pyrethroid Killem insect aerosol tetramethrin 0.2% + ∆-phenothrin 0.08% G pyrethroid Gramoxone paraquat 24.75% P heterocyclic Fungazil 75% S.P. imazalil 75% R heterocyclic Thiram 80% W.P. thiram 80% (disulphide) R carbamate (fungicide) Tritifix MCPA/amine 41.5% A phenoxy acid Copper fungicide copper oxychloride 88% A inorganic compound Copper oxychloride 50 E.C. copper oxychloride 50% A inorganic Dormex cyanamide 49% A inorganic amide Agri Dust dusting sulphur 65% + A inorganic compound copper oxychloride 6.5% inorganic salt +malathion 5% A OP Arsenal imazapyr G heterocyclic Cosan wettable sulphur sulphur 80% G inorganic compound Lime sulphur polysulphide sulphur 24.8% G inorganic compound Racumin rat poison coumatetralyl Na + R heterocyclic Basagran bentazone 48% A heterocyclic Bladex 5 S.C. cyanazine 50% A heterocyclic Citrocyclin 90 tetracycline + hydrochloride 90% A heterocyclic Funginex triforine 18.7% G heterocyclic Fumigas 10 ethylene oxide 10% P organic compound Agrifume EDB 4.5 ethylene dibromide 42.2% P organohalide Agrithrin 20 E.C. fenvalerate 20% A organic acid derivative Daconate 6 MSMA 48% A organic acid derivative MSMA MSMA 48.4% A organic acid derivative Snail and slug killer metaldehyde 2% G organic acid derivative Norax ready mixed warfarin 0.0375% A organic compound NABU sethoxydim 20% G organic compound Alachlor alachlor 48% P acetanilide Ronstar FLO oxadiazon 240 g/l A organic amine Weedkiller M M.C.P.A. 400 g/l potassium salt A organic salt Atrazine 5 G atrazine 6.25% G organic acid derivative Bayer Diuron 80 W.P. diuron 80% G dimethylurea Bayleton 5% W.P. triadimefon 5% G organic derivative Bayton 15% triadimenol 15% G alcohol Benlate benomyl 50% G carboxylic acid derivative Mitac amitraz 20% A organic acid derivative continued… © 2003 Milton D. Taylor, Stephen J. Klaine, Fernando P. Carvalho, Damia Barcelo and Jan Everaarts Pesticide use in Zimbabwe 27 Table 3.2 continued Brand name Active Poison Type of ingredient group b compound Cotogard 500 F.W. fluometuron 25% + prometryn 25% G urea derivative triazine Gesagra 500 F.W. metolachlor 25% + triazine 23.5% G acetamide Gibberellic acid gibberellic acid 32% G organic acid Karathane 2% dust dinocap 2% G nitrophenol Dithane M-45 W.P. mancozeb 80% G organic acid derivative Dithane M-45 mancozeb 80% G organic acid derivative Orchard oil mineral oil 99.7% G petroleum oil Orchex oil 695 mineral oil 99.25% G petroleum oil Pilot S.C. quizalofop-ethyl G organic compound Ronstar Flo oxadiazon 36% G organic amine Roundup glyphosate 41% G phosphoglycine Rovral 250 S.C. iprodione 25% G carboxamide Rovral iprodione 50% G carboxamide Sprayquip tak n-decanol 79% G petroleum oil Stomp 500E pendimethalin 50% G nitrobenzamine TCA 90 grass killer sodium trichloro- acetate 90% G organic salt Tordon 101 mixture 2,4-D amine salt 39.6% P phenoxy acid + picloram 10.2% carboxcylic acid derivative Gesaprim 500 F.W. atrazine 47.0% G atrazine Gesagard 500 F.W. prometryn 50% G triazine Gardomil 500 F.W. terbuthylazine 36.7% + metolachlor 12.5% G triazine acetamide Tetradifon 8 E.C. tetradifon 8% G sulfone Notes: a Reproduced with permission, Table 23 in SADC ELMS Report Series 35 (1993). b Poison group (see text for LC 50 s corresponding to each group): A (amber) = toxic; G (green) = non-toxic; R (red) = highly toxic; P (purple) = extremely toxic. Table 3.3 List of commonly used dipping chemicals in Zimbabwe a Brand name Active ingredient Poison group % a.i. Class of compound Fendona alphacypermethrin G 5 pyrethroid Paracide alphacypermethrin G 7 pyrethroid Triatix D amitraz G 12.5 amidine Barricade cypermethrin A 15 pyrethroid Ectopor cypermethrin G 2 pyrethroid Grenade cyhalothrin G 5 pyrethroid Ektoban cypermethrin G 2.5 pyrethroid Decatix deltamethrin G 5 pyrethroid Sumitik fenvalerate A 20 pyrethroid Bayticol flumethrin G 20g/L pyrethroid Drastic Deadline flumethrin G l0g/L pyrethroid Note: a Adapted from SADC ELMS Report Series 35 (1993). © 2003 Milton D. Taylor, Stephen J. Klaine, Fernando P. Carvalho, Damia Barcelo and Jan Everaarts 28 Mark F. Zaranyika Pesticide pollution from agriculture Zimbabwe is a landlocked country where elevation and rainfall are highly correlated. Rainfall varies from below 300 mm annually in the low-lying areas in the south and southeast, to more than 1,500 mm in the mountains bordering Mozambique. Rain falls from November to March, and only about one-third of the country is suitable for intensive agriculture. Figure 3.2 shows the agro-ecological regions of Zimbabwe (ENDA, 1991). Traditionally tobacco has been the primary agricultural commodity, although cotton, tea, citrus, livestock, wheat, sugar, and maize are also important. Figure 3.3 shows that all rivers within Zimbabwe originate from the high veld – veld or veldt is the extensive grassland region of eastern and southern Africa – where most of the intensive agriculture is practiced. These rivers drain to the Zambezi River and Lake Kariba in the north, and to the Limpopo River in the south. The Zambezi and Limpopo rivers are the two major rivers flowing to the Indian Ocean. A major climatic factor in the dispersal of pesticides from agricultural use in Zimbabwe is the fact that rain is usually in the form of short, heavy tropical storms which result in high erosive runoff during the periods that most pesticides are applied in agriculture, i.e. between November and January. This high erosive runoff leads to silting behind dams, so that much of the applied pesticides find their way directly into river and lake sediments (Zaranyika and Makhubalo, 1996). Evidence of a build-up of OC pesticide residues in Lake Kariba sediments has been reported (Zaranyika et al., 1994). Recently, smallholder vegetable production has rapidly expanded in Zimbabwe. Sibanda et al. (2000) found these small farmers use some cultural control methods and occasionally botanical pesticides but for the most part they rely on conventional synthetic pesticides for controlling the range of serious pests and diseases that affects nonindigenous vegetables. Synthetic pesticides are usually applied using lever-operated knapsack sprayers, although occasionally less orthodox application methods are employed. The primary concerns based on these practices are due to shortcomings in protective clothing for applicators, large deviations from recom- mended doses (based on the adage that if a little is good, then more is better), and excessive runoff to the soil. Both of the latter concerns can lead to a build-up of pesticide residues in streams and lakes. PESTICIDE USE IN THE CONTROL OF DISEASE VECTORS Tsetse fly infestation in eastern central Africa Tsetse fly infestation in Africa was reviewed by Ford (1971). In southern east-central Africa, infestation is mainly by Glossina morsitans Westwood (Diptera: Glossinidae) and G. pallidipes Austen. Figure 3.4 shows the areas infested. G. morsitans infests the Brachystegia-Fulbernardia woodlands of Mozambique and Zimbabwe below © 2003 Milton D. Taylor, Stephen J. Klaine, Fernando P. Carvalho, Damia Barcelo and Jan Everaarts Pesticide use in Zimbabwe 29 1,200 m above sea level, and the Colophospernum Mopane woodlands in the Zambezi valley. G. pallidipes is also found throughout these areas inhabiting thicket or forest-edge areas. Until eliminated by insecticides from Zululand (du Toit, 1959), it extended further south in Africa than any other species. Figure 3.5 shows the distribution of G. morsitans and G. pallidipes in Zimbabwe, southern Mozambique and South Africa in 1959. Tsetse fly in Zimbabwe Zimbabwe forms a single natural geographical system, centered upon the watershed that separates the Zambezi from the Limpopo and Sabi-Lundi river systems (see Figure 3.2 Agro-ecological regions of Zimbabwe (from ENDA-Zimbabwe, 1991) © 2003 Milton D. Taylor, Stephen J. Klaine, Fernando P. Carvalho, Damia Barcelo and Jan Everaarts 30 Mark F. Zaranyika Figure 3.3 Zimbabwe with its major drainage systems Source: Billings and Phelps (1972). Figure 3.4 Distribution of G. morsitans and G. pallidipes in S.E. central Africa (adapted from Ford, 1971). With permission of Oxford University Press. © 2003 Milton D. Taylor, Stephen J. Klaine, Fernando P. Carvalho, Damia Barcelo and Jan Everaarts [...]... 2 .31 0.42 0. 73 0. 93 6. 43 1.84 7.25 5.87 11.62 1.10 1. 63 1.49 2.28 13. 50 4.95 3. 91 3. 13 1.24 0.58 1.02 1.86 p,p´-DDT ∑ DDT d 3. 15 21. 93 4.24 12.52 5.02 75.09 53. 31 67.71 64.26 83. 71 17 .32 38 .51 23. 62 30 .48 88.71 31 .28 45.40 21.41 19.17 5.04 9.19 38 .39 – 2.26 0.09 1.65 0 .30 20 .31 5.94 10.26 9 .31 18.90 1.49 2.04 1.62 4.12 12.47 4 .37 3. 94 3. 03 1 .30 0 .39 0.68 2.20 Notes: a Fat samples extracted using hexane... 1 .35 1 1 .35 1 0.004 0.0 03 0.004 0.005 0.006 0.004 0.005 0.045 0.061 0.154 0.202 0. 538 0.280 0.2 13 3.08 3. 76 3. 13 3 .38 8.01 4.46 8.95 0.69 0.90 0.66 0.64 1.85 0.78 2.69 0.51 0.60 0.48 0.52 1. 53 0.68 2.72 4.28 6.26 4.27 4.54 11 .39 5.92 14 .36 0.0 53 0. 038 0.248 0.270 0.185 0.1 43 0.1 43 0.007 0.0 03 0.004 0.148 0.092 0.0 43 3.26 4.25 3. 07 0.71 0.70 0. 23 0.52 0. 53 0 .34 4.49 5.48 3. 64 0.221 0.1 53 0.110 p,p´-DDE 0.029... 16 .30 8.62 5.66 55 .32 58.04 35 .82 17.69 82.99 6.80 14.51 4.99 7.26 o,p-DDE 0.28 0.28 0.08 0.27 0.15 2. 23 0.97 2.66 2.50 3. 86 0 .32 0.65 0.20 0.69 8. 23 0.66 0.90 0.52 0.24 0.15 0.16 0.51 p,p´-DDE 1.91 17.08 3. 65 9.87 3. 08 46.12 44.58 47.54 45.26 49 .33 14.41 34 .19 20 .31 23. 39 21.97 20.04 36 .65 14. 73 16.69 4. 73 6.87 33 .81 o,p-TDE 0.46 – – – 0.56 – – – 1 .32 – – – – – – 1.26 – – – – 0.46 – p,p´-TDE 0.50 2 .31 ... 0.69 3. 24 3. 14 ND 0.002 0.210 0.218 5.02 3. 11 0.72 0.72 0.74 0.66 6.48 4.49 0.0 03 0.044 0.0 13 0.0 83 4.60 5. 43 0.51 2. 63 0.61 1.97 5.72 10. 03 0.046 0.250 16.29 5.68 3. 94 25.91 0.0 63 0.011 0.018 0.010 0.011 0.009 0.011 1.262 1.548 1 .39 8 1.211 1.664 1.506 6.22 10 .31 6.21 5.99 5.89 6.49 1.29 2.05 1.40 1.21 1.21 1.49 1.24 1.89 1.14 1.11 1.22 1 .33 8.75 14.25 8.75 8 .31 8 .32 9.28 1. 530 1 .35 6 1.0 23 1.220 1 .35 1... insecticide residues in 15 crocodile eggs (µg g–1 dw) from Lake Kariba, Zimbabwea Nest and egg number α-BHC β-BHC Dieldrin p,p´-DDE p,p´-DDD p,p´-DDT ∑ DDT Mwenda River mouth M6 i M7 i M7 ii i Is.c7 Is. 13 i Is.27 i Is.27 ii Is .34 i Is .35 i K1 i K3(1) i K3(4) i i i i –b – – – – – – – – 0.18 0.07 0.22 0.01 – 5. 63 – – – – – – – – – 9. 63 1.01 6 .38 – – 24.5 – – – – – – – – – 1.19 – – – – – 1 .33 1.97 1.98 2.09 0. 53. .. al., 1980 b En dash (–) indicates residue not detected c Is represents island © 20 03 Milton D Taylor, Stephen J Klaine, Fernando P Carvalho, Damia Barcelo and Jan Everaarts Mark F Zaranyika Collection site Pesticide use in Zimbabwe 43 Table 3. 10 OC insecticide and PCB residues in crocodile eggs from Zimbabwe (µg g–dw)a α-BHC β-BHC 0.0 03 0.0 03 NDb 0.005 0.004 0.002 0.002 0.0 03 0.0 03 0.002 0.002 Mpalangena... whose diet includes aquatic animals, contained pesticide residues At Lake Kariba, pesticide residues were found in fish-eating birds taken from basins that receive drainage from agricultural areas Similar findings were reported by Wessels et al (1980) following a study involving analysis of crocodile eggs from Lake Kariba, see Table 3. 9 This study found increased residue levels in one basin of the lake,... Zimbabwe 37 The surveys by Billings and Phelps (1972) and Whitwell et al (1974) were carried out following the tsetse fly control campaigns in 1962 to 1967 with dieldrin, and in 1968 to 1972 with DDT The surveys were conducted by analyzing birds’ eggs and other biological samples collected from various part of the country (see Tables 3. 7 and 3. 8 and Figure 3. 2) The pesticides tested for in the studies included... dieldrin, aldrin, and endosulfan Although the surveys did not find evidence of a heavy build-up of pesticides in the terrestrial environment as a result of the anti tsetse spraying, it did find evidence of a build-up of pesticides in the terrestrial and aquatic environments from agriculture The study by Billings and Phelps (1972), involving analyses of eggs, embryos, and body fat of crocodiles, and livers... using 3. 1 percent dieldrin emulsion in the south-east Zimbabwe–Mozambique border region 1962–67 Year No of teams Quantity used (L) Approx area sprayed (km2) 1962 19 63 1964 1965 1966 1967 2 2 3 5 6 9 46,2 73 45,569 75,645 174,907 219,026 1,6 13, 80 900 1,160 1 ,30 0 2,070 1, 530 2, 130 a Note: a 830 km2 in Zimbabwe and 1 ,30 0 km2 in Mozambique Table 3. 5 Spraying operations in the south-east Zimbabwe–Mozambique . 1,160 1964 3 75,645 1 ,30 0 1965 5 174,907 2,070 1966 6 219,026 1, 530 1967 9 1,6 13, 80 2, 130 a Note: a 830 km 2 in Zimbabwe and 1 ,30 0 km 2 in Mozambique. Table 3. 5 Spraying operations in the south-east. TTL d 0.79 3. 68 2.10 6.57 1 .33 Barbel abd. fat Chipinda 3. 41 11.4 1.88 16.64 ND e Darter liver Chipinda ND 6. 43 ND 6. 43 ND Darter abd. fat Chipinda ND 23. 2 ND 23. 2 ND Flycatcher liver Harare 1. 53 29.6. largest man-made lakes. It was constructed in the mid-1950s, started to fill in 1958, and reached full capacity in 19 63. Situated in south-central Africa (between Lat. 16 ° 30 ' to 18 ° S, and Long.