The united republic of tanzania agricultural sector development program
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- Table 4.46: Major pests of mango and their recommended management practices
4.3 ZANZIBARFood crops It is estimated that food crops cover about 60% of the total cultivated land (130,000 ha) of Zanzibar (ZIDP, 2002). Rice ranks first in the list of important food crops in Zanzibar. Other common food crops include cassava, banana, maize, sweet potatoes, legumes, maize, sorghum and yams. The acreage of the major food crops are shown in Table 4.33 and the production trend of the food crops for the past ten years are shown in Table 4.34. Table 4.33: Acreage of Food crops in Zanzibar
Source: Ali (1995). Table 4.34: Production of the common food crops in Zanzibar in tons, 1990/1991 –1999/2000
Source: MANREC, Zanzibar Tanzania Report on the implementation of the World Food Summit Plan of Action. In: The study on the Zanzibar Irrigation Master Plan in the United Republic of Tanzania, Master Plan Report, 2002, Nippon Koei Co., Ltd Rice Rice is the staple food in Zanzibar. Almost every rural household strives to cultivate some rice land for home consumption in the sense that it alleviates the need to buy rice. At present, about 16,000 tonnes of rice are produced annually and about 80,000 tonnes of rice are imported yearly to meet the domestic demand. Table 4 shows the supply of rice in Zanzibar. Table 4.35: Supply of rice in Zanzibar, 1984/1985 – 1994/1995
Source: Food for Self Sufficiency in Zanzibar, 1996; Status of Irrigation Development in Zanzibar, 2001. In: The study on the Zanzibar Irrigation Master Plan in the United Republic of Tanzania, Master Plan Report, 2002, Nippon Koei Co.
Rainfed rice In Zanzibar, the total cultivated area under rainfed rice is 19,885 ha. Out of these, 11,500 ha in Unguja and 8,385 ha in Pemba. According to ZIDP (2002), on Unguja rainfed rice is concentrated in the few but larger hydromorphic valleys such as Kilombero (1,145 ha), Kisima mchanga (800 ha), Cheju (600 ha), Muyuni (586 ha) and Bumbwisudi (560 ha), whereas in Pemba there are several small valleys such as Maotwe (120 ha), Kwapweza (95ha), Mipopooni (80 ha), Ng’wia (73 ha) and Mgong’ombe (72 ha). Rainfed rice is grown solely dependent on the Masika rainfall. The period of rain fed rice cultivation is December till June or July. Sowing is done on the isolated showers between January and February after ploughing and harrowing by tractor or by hand hoe. Weeding starts soon after planting, by hand pulling or by using a small hoe, or herbicides such as Satunil. The advantage of planting in the dry season is the easy accessibility to the field for weeding, and slow weed growth. Stem elongation and booting takes place in April, about one month after the onset of the Masika rains. The crop is harvested in June or early July. In the usual farmer practice, small amounts of Triple Super Phosphate and Urea fertilizers are used, and insecticides are sometimes used against insect pests. Crop rotation is not practised, but after the rice harvests some farmer’s plant cowpeas, maize or sweet potatoes as off-season crops. The rice beetle (Heteronychus andersoni) is an important pest in rainfed rice in Zanzibar. According to Jaan van Weel (1992), the damage is caused only by the adult beetles that come to the soil surface at night. They crawl on the surface or make shallow tunnels just below the surface. They actually feed on the growing point of the rice plants. The leaves stem and roots are not touched. Damage can easily be recognised by the drying out of the central leaf, and by the fibrous hole in the bottom of the plant. The damage by rice beetle is usually heaviest in the first two weeks after germination and again immediately after the start of the Masika rains. The PPD – Zanzibar has carried out an extensive research to control this insect pest. The control measures of this insect pest and other pest problems are summarised in Table 5. Table 4.36: Major pests of rainfed rice and their recommended management practices
Source: Recommendations of the Plant Protection Division on the major pests and diseases in Zanzibar The average rice yield under rainfed production system is shown in the Table 4.37. Table 4.37: The average rice yield of different varieties under rainfed production system
Source: Terminal report IPPM Project (TCPURT/0065 [T]), 2002. Irrigated rice For several decades, some farmers in Zanzibar particularly in Pemba have been practising traditional irrigation on rice in the form of water harvesting technique. However, since mid 1970’s the Revolutionary Government of Zanzibar (RGZ) under the support the donor funded projects had started to establish the rice irrigation schemes in both Unguja and Pemba for the purpose of boosting the production of paddy to small holder farmers. Based on ZIDP (2002), currently there are a total of 341.6 ha (Unguja 268 ha and Pemba 73.6 ha) under irrigation. In Unguja, the key irrigation areas are Cheju (42 ha), Mwera (12 ha), Bumbwisudi (136 ha) and Mtwango (78 ha). Whereas in Pemba are Kinyakuzi (8ha), Saninga (16 ha), Tungamaa (6 ha), Mangwena (10 ha), Kwalempona (13.6 ha) and Tibirinzi (6 ha). Under the irrigation system, rice is grown in two seasons, Masika long rain and Vuli short rain. The average rice yield is 4.4 tons/ha under IPPM practices versus 2.2 tons/ha under farmers’ practice (Terminal report IPPM Project TCPURT/0065 [T], 2002). The main pests of irrigated rice in Zanzibar are Hispa beetle (Trichispa sericea), Hydrellia sp, and Maliarpha separatella. Other pests’ occassionally do some minor damage, but are rarely of economic importance. Such pests are Stemborer (Chilo spp) and leaffeeders such as Borbo borbonica (rice skipper), Gryllotalpa africana (mole cricket), Marasmia trapezalis (web worm) and Nymphula depunctalis (rice case worm). The recommended control measures of the major pests of irrigated rice are summarised in Table 7. Table 4.38: Major pests of irrigated rice and their recommended management practices
Source: Recommendations of the Plant Protection Division on the major pests and diseases in Zanzibar (Version 2002). Cassava Cassava is considered to be the second important food crop in Zanzibar. It is widely grown by over 90% of the farmers in the islands (Ali et al, 1995). It has been noted that cassava is an important crop in coral rag areas due partly to its drought resistance (Borsa, 1987). Over 18,000 ha of cassava are estimated to be grown all over the islands due to its adaptation of diverse soil and environmental conditions (Saleh, 2000). In the plantation zones, cassava is commonly grown in pure stand or inter-cropped with sweet potatoes. Whereas in the coral rag zones, it is often planted with pawpaw, pigeon pea, cowpea and green gram (Fowler, 1997). Yields can be as high as 10-15 tons/ha in plantation zones but on poorer soils and “uwanda” soils yields are in the range 5 – 7 tons/ha. In the coral rag zones, yields are even less due to lower plant population and increased severity of pest and diseases (Fowler, 1997). The overall trend in cassava production in Zanzibar has shown to decline (see Table 3). From the results of various Participatory Rural Appraisals (PRA) carried out during the Dutch-funded IPM project (1994–1998) and preceded FAO-funded IPPM project (March 2001–December 2002), it revealed that the problem of low productivity of cassava in Zanzibar is mainly attributed by the followings: Declining soil fertility in the farmers fields, Pests and diseases, particularly Cassava Mosaic Disease (CMD), Cassava Brown Streak Disease (CBSD), Green Mites and Cassava Mealybugs, Shortage of disease free planting materials. According to Saleh (2000), spreading of the cassava viral diseases has been accelerated by selling or exchange of diseases planting materials from one area to another. The recommended control measures of the major pests of cassava are summarised in Table 4.39. Table 4.39: Major pests of cassava and their recommended management practices
Source: Recommendations of the Plant Protection Division on the major pests and diseases in Zanzibar Banana and plantains Bananas and plantains rank third in the list of the most important food crops in Zanzibar. It is estimated that the total area under production of this crop is 6,500 hectares and produces approximately 10.5 tons/ha (MANREC, 2002). There are about twenty two varieties of banana and plantain grown in Zanzibar. These varieties are both cooking and dessert bananas. Smallholder farmers are the main producers of banana and plantains. Their production is geared for home consumption and surplus is sold on local markets. From the results of various Participatory Rural Appraisals (PRA) carried out during the Dutch-funded IPM project (1994–1998) and preceded FAO-funded IPPM project (March 2001 – December 2002), it revealed that the major constraints facing bananas/plantains production on Zanzibar are: declined soil fertility which is caused by continous planting on the same plots pest and diseases, including Black sigatoka (Mycosphaerella fijiensis), Panama disease (Fusarium oxysporium f. sp cubense), nematodes and Banana weevils (Cosmopolites sordidus). inefficient management practices. lack of pest- and -disease free planting materials. low level of agricultural knowledge to farmers. shortage of land for establishment of new plots. The recommended control measures of the major pests of banana are summarised in Table 4.40. Table 4.40: Major pests of banana and their recommended management practices
Source: Recommendations of the Plant Protection Division on the major pests and diseases in Zanzibar Sweet potato In Zanzibar, sweet potato is the second most important root crop after cassava. It is one of the important cool season crops and the main time for planting is in June with minor plantings throughout the year. The crop begins to mature after 3 to 4 months. Sweet potatoes are often planted as a catch crop among cassava and as such can yield up to 2 ½ tons per acre (6.250 kg/ha). The young leaves can be used as spinach. Sweet potatoes are mainly intercropped with cassava; only 4.7% is grown as a sole crop (Wirth et al., 1988). When intercropped with cassava, it has little adverse effect on the cassava. In areas they are monocropped only one weeding is required as the crop covers the ground and smothers weeds. Planting material must be maintained between seasons and this can be a problem and leads to a shortage of planting material. (Fox et al., 1994) The recommended control measures of the major pests of sweet potato are summarised in Table 4.41. Table 4.41: Major pests of sweet potato and their recommended management practices
Source: Recommendations of the Plant Protection Division on the major pests and diseases in Zanzibar Maize and Sorghum Maize and sorghum are important cereal crops after rice in Zanzibar particularly in the coral rag zones (Borsa, 1987). Small-scale farmers in both plantation and coral rag zones mainly cultivate these crops during Masika and Vuli seasons. In coral rag zones, these crops are commonly grown early in the cycle after land clearing to take advantage of high soil fertility and low weed infestation. Often, farmers’ plant local varieties and their planting are irregular. At the seed and seedling stage, rats and wild fowls can attack maize and sorghum in the coral rag areas (Borsa, 1987). As the seedlings grow to leaf whorls, they are subjected to the attack of the stemborer larva that mine on leaf sheath and then migrate down to the stems where they make tunnels on the young stems and eventually resulting to destruction of the growing points. It is estimated that yield losses due to stemborers is 30 –40% (Allertz et al., 1988). At cob formation, monkeys and pigs can attack the crop. Moreover, maize rust and maize streak diseases are common problem in the coral rag zones. Also, the parasitic weed, Striga spp, is often found in many areas in the coral rag zones. For several decades, farmers have been controlling the stemborers through cultural practices, such as residue management and manipulation of planting date or mechanical measures. In 1980’s the use of granular insecticides, such Dipterex and Thionex 3G, has been promoted through the selling of these insecticides at high-subsidised price. However, as government subsidies on pesticides were removed in the 1990’s, it has greatly increased the cost of production to farmers and minimised their use. Since 1999 the International Centre of Insect Physiology and Ecology (ICIPE) based in Kenya, with funding from the Directorate General for International Cooperation (DGIS) of the Government of the Netherlands, has been implementing a biological control project on cereal stemborers in Africa. The primary target of the project is the exotic stemborers, Chilo partellus, which evaded eastern Africa sometime after the turn of the century. The efforts of the project resulted into the release of Cotesia flavipes, an exotic parasitoid from Asia, in Kenya, Mozambique, Somalia, Uganda, Zambia and Malawi. There was firm evidence that the parasitoid was established in Kenya and Northern Tanzania, and is expected to establish in many other areas of eastern Africa. In preparation for the release of C. flavipes in Zanzibar, the Plant Protection Division (PPD) conducted surveys of maize and sorghum stemborers and their native parasitoids of the island of Unguja in 1995 and 1996. The results of the survey clearly indicated that 1) C. partellus was the predominant stemborers and 2) parasitism of C. partellus by native parasitoids was very low. Then, several releases of Cotesia flavipes were done in both Unguja and Pemba islands. So far from field assessments, the parasitoids have been found to establishing on the farmers’ fields. This project is still going on. The recommended control measures of the major pests of maize and sorghum are summarised in Table 4.42. Table 4.42: Major pests of maize and sorghum and their recommended management practices
Source: Recommendations of the Plant Protection Division on the major pests and diseases in Zanzibar Grain legumes Grain legumes (include green gram, cowpeas, pigeon peas and groundnut) are widely grown in Zanzibar. However, up to 1992 they had only a minor place in the agricultural research in Zanzibar (Rowland in Smith, 1992a). The MANREC had realised the gap, and nowadays there are number of on-going research activities on these crops. The recommended control measures of the major pests of grain legumes are summarised in Table 4.43. Table 4.43: Major pests of grain legumes and their recommended management practices and their recommended management practices
Source: Recommendations of the Plant Protection Division on the major pests and diseases in Zanzibar CASH CROPS Currently, clove is the major cash and export crop of Zanzibar. Since last decade, coconuts are no longer an important export crop as used to be in the past. This is mainly due to dumping effect of imported oils in Zanzibar. Nowadays the importance of coconuts is confined to the domestic market. In early 1990’s, mango was identified as one of the candidate crop that could supplement clove. The export of mango has then increased from 16 tons in 1992 to 100 tons in 1995 (PPD – record data of export certification). The major export variety is ‘Boribo Muyuni’ and is well popular in the Gulf countries markets particularly in between October – March, when it’s an off-season for the major mango suppliers such as India and Pakistan. However, since 1996/97 mango season, an outbreak of mango fruitfully (Ceratitis cosyra) occurred in Zanzibar and caused yield losses of 50-80%. Subsequently, this led to collapse of mango industry, both internal and external. 2.2.1 Cloves In Zanzibar, clove industry was introduced in mid-19th century and for more than 100 years it has been the most important foreign exchange earning crop (Martin, 1989). Besides the falling of price of clove in the World Market, the clove is still the major source of Government revenue. Moreover, cloves provide a source of income to clove farmers as well as to thousands of clove pickers who are employed each year for harvesting. The most important diseases of the clove trees are Sudden Death and Acute Dieback. There are relatively few insect pests of cloves in Zanzibar but one of the most serious problems is caused by termites (Macrotermes spp). The recommended control measures of the major pests of clove are summarised in Table 4.44. Table 4.44: Major pests of cloves and their recommended management practices
Source: Recommendations of the Plant Protection Division on the major pests and diseases in Zanzibar Coconuts According to Gajian (1987), there are 60,000ha under coconut on Unguja and 18,000ha on Pemba. Most coconut trees are found in the plantation zone. With an average yield of 28.3 nuts per palm and a total palm population of 4.7 million trees, the total coconut production per year is estimated to be 132.6 million nuts (Heydon, 1987). Of these, 84.7 million (64%) are consumed fresh, 47.3 million nut (36%) may be processed into copra (Oswald and Rashid, 1992). Coconut is the main source of plant oil to the majority of households of Zanzibar and is used for cooking of variety of foods. Besides that the tree also supplies roofing material, beverage, fibres used for rope production, firewood for cooking and oil for soap production. The by-product of coconut oil processing, the coconut cake, may be used as animal feed (Gajian, 1987). Declines in coconut production and yield losses are due to overawed trees, poor maintenance because of low producer prices and coconut pests (Gajian, 1987). There are 21 species of pests observed in Zanzibar (Feijen et al., 1988). Among these, the most important pests of coconut are the coconut bug (Pseudotheraptus wayi), the rhinoceros beetles (Oryctes monoceros Ol.) and termites (Macrotermes spp). The recommended control measures of the major pests of coconuts are summarised in Table 4.45. Table 4.45: Major pests of coconuts and their recommended management practices
Source: Recommendations of the Plant Protection Division on the major pests and diseases in Zanzibar Mango Mango ranks first in the list of fruits preferred by Zanzibaris. It’s a good source of nutrients and plays a big role in the rural food security as well. Generally, mango is planted in plantation zone both in Unguja and Pemba islands. But due to good market prospects that were noticed in early 1990s, many farmers within the area of coral zone have started to grow mango. Shortage of land within plantation area is also a reason to plant mango within coral rag zone. The 1989 crop survey revealed that there are 90,000 mango trees which covering about 750 hectares of land. Most of the farmers own few to several mango trees. In an effort to revive the economy of Zanzibar, in early 1990’s mango was identified as one of the candidate crop which could supplement clove. In 1995, RGZ with assistance of the British-funded ‘Zanzibar Cash Crops Farming Systems Project’ launched ‘The Mango Strategy Plan’ that aimed at increasing the export of mango from 100 ton to 1,500 – 2,000 tons within the next ten years. Many farmers in rural areas have shown a great interest in mango production for the hope of improving their standard of living. The government responded positively to this situation by raising a number of seedlings in its nurseries as well as training and promoting individual farmers to establish their own nurseries. Also, a lot of ‘top works’ were done on old mango trees to improve the quality of seedlings and meet the farmers’ demand of planting materials. According to Ajali (2,000), the mango fruitfly (Ceratitis cosyra) had been reported to exist in Zanzibar for quite a long time, but no cases of heavy infestation have been experienced before until the 1996/97 mango season when a long spell of drought hit the islands. Since then, farmers have witnessed very big yield losses ranging from 25-50% due to an outbreak of mango fruitfully. There are other species responsible for the damage, such as Ceratitis rosa and Bastocera spp. But the major and most destructive one is Ceratitis cosyra. This species seems to be well established in Zanzibar as it has a number of alternative hosts, such as guava, Durian, soursop and rubber vine fruits. Since this outbreak, the export of mango has declined sharply and threatening the income and food security of many rural households. Since then, the Plant Protection Division of the Ministry of Agriculture, Natural Resources, Environment and Cooperatives – Zanzibar, have been collaborating with the International Center of Insect Physiology and Ecology (ICIPE) based in Kenya, through the African Fruit Fly Initiatives program in acquiring and updating technology of fruit fly management. With this program, some accomplishments have been attained, such as: Assessment of the damage of fruitfully and its alternative hosts. Use of traps for monitoring purposes. Testing of different types of the attractants and lures. The recommended control measures of the major pests of mango are summarised in Table 4.46. Table 4.46: Major pests of mango and their recommended management practices
Source: Recommendations of the Plant Protection Division on the major pests and diseases in HORTICULTURAL CROPS History shows that Zanzibar has been well known as a home of many tropical fruits such as citrus, mango jack-fruit, roseapple, pineapples, papaya, banana, tamarind, guava, custard apple, grapes and mulberries (Rowland in Smith, 1992b). Since early 1930’s Kizimbani research station has been the front liner in doing research on a number horticultural crops as well as for multiplication and distribution of planting materials to the farmers in Zanzibar. Citrus Citrus is one of the important fruits in Zanzibar and is commonly consumed for improvement of the nutritional status of the households. Small-scale farmers in both plantation and coral rag zones mainly grow it. Since 1970’s many small-scale farmers have shown interest in citrus production due to its potentiality of generating high income which help them in solving their households’ problems. In 1999, the PPD in collaboration with GTZ conducted an extensive survey in Unguja and Pemba to assess the incidence of citrus woolly whitefly (Aleuronthrixus floccosus) and other insect pests of citrus. From this survey, the major pests of citrus were leaf miners (Phyllocnistis citrella) and black flies. The citrus woolly whitefly was not found to be an important pest of citrus. The recommended control measures of the major pests of citrus are summarised in Table 4.47. Table 4.47: Major pests of citrus and their recommended management practices
Source: Recommendations of the Plant Protection Division on the major pests and diseases in Zanzibar Pineapples Pineapple is one of the important fruits that is grown by small scale farmers in Zanzibar. Since late 1990’s, many farmers especially in the plantation zones have been prompted to grow this crop due to high price offered at the market as the result of expansion of tourism industry. The major pineapple growing areas on Unguja are Machui, Bumbwisudi, Mahonda and Donge. Pineapple mealybug (Dysmicoccus brevipes) is an endemic pest in Zanzibar and is a vector of the wilting disease on pineapples. Moreover, it is believed that movement of infested planting materials from one location to another has contributed to the spreading of this disease. According to the results of the pineapple mealybug survey which was carried out in 1994 by PPD, it showed that the majority of the fields surveyed did not show the effect of mealybug in plant but the overall result shows significant effect of mealybugs to pineapple wilting. It was noticed that the spread of this disease is accelerated by the lack of knowledge of farmers on the relationship of mealybug and the disease. The recommended control measures of the major pests of pineapples are summarised in Table 4.49. Table 4.49: Major pests of pineapples and their recommended management practices
Source: Recommendations of the Plant Protection Division on the major pests and diseases in Zanzibar Vegetables Vegetable crops such as tomato, eggplant, amaranths, cucumber and radish are traditionally grown in Zanzibar. The production of vegetable crops, especially those of temperate type such as cabbages, sweet peppers, carrots and onions, are also increasingly grown since the last decade. This is largely attributed to the expansion on tourism industry; where by the domestic market for some vegetables has grown. The availability of a reliable market together with good prices that some vegetables fetch in the market prompted farmers to engage in commercial production. The best season for vegetable production is between June- September where the weather is relatively dry and cool. However, nowadays off-season production is becoming more important because farmers have realized that they can earn more income on a small plot. Therefore the area under vegetable production has been extended in the last few years. Similarly, the farmers now produce more than five varieties of vegetable crops per season. It has been estimated by Bruin and Meerman (2001) that the total acreage on Zanzibar under vegetable production is 1,200 ha (9% of the total cultivated land [130,000 ha]). Out of these, tomato occupies 586 ha, amaranthus 334 ha and eggplant 307 ha. From the results of various Participatory Rural Appraisals (PRA) carried out during the Dutch-funded IPM project (1994–1998) and preceded the FAO-funded IPPM project (March 2001–December 2002), it was revealed the pests are among the overriding constraints of vegetables in Zanzibar. Specific pest problems on the major vegetables are shown in Table 4.50. Table 4.50: Pests problems on the major vegetables
Source: Bruin and Meerman, 2001. The recommended control measures of the major pests of vegetables are summarised in Table 4.51. Table 4.51: Major pests of vegetables and their recommended management practices
Source: Recommendations of the Plant Protection Division on the major pests and diseases in Zanzibar MIGRATORY AND OUTBREAK PESTS The key migratory and outbreak pests of economic importance in Zanzibar are armyworms (Spodoptera exempta), birds (notably India crow) and rodents (particularly the field rats). The elegant grasshoppers (Zonocerus elegans) are of less economic importance. The control management of all these migratory and outbreaks (with exception of the Indian crows which is controlled by the Department of Environment [DoE]) is co-ordinated by the Plant Protection Division - Zanzibar. Armyworms Although army worm (Spodoptera exempta) is not as great a problem on the islands as it is on Tanzania Mainland, there are from time to time reports of outbreaks damaging rice (particularly at Cheju, Kibokea, Kilombero, Muanda and Muyuni), and sometimes in maize and sorghum fields in the coral rag areas. According to Mallya (1991) its likely that there is a permanent population of the army worm which persist at low density in the solitarious phase, but occasionally conditions arise that allow numbers to increase to a level at which outbreaks of the gregarious phase can occur. Spraying campaigns Normally, either farmers or MANREC staff at the Regional/District level reports the outbreaks of the armyworms to PPD. More often, the outbreaks are not reported in time (2-4 days later). Immediately after an outbreak is reported, the Field Service (FS) staffs of PPD in collaboration with Research staff of PPD have to survey the attacked areas. The decision of spraying is taken when the threshold level is reached (i.e. average population of the armyworms per square meter is greater than 15). PPD has then to provide the spraying equipment and free pesticides to the farmers. The spraying team of PPD and some Kilimo staff (in case of those areas that are under the Rice irrigation project and Rainfed Rice Development Authority) are involved in the spraying exercise. FS staff supervises the whole spraying exercise. In addition to that, Block Extension Officers and Shehas are supposed to mobilize the farmers to co-operate fully in the spraying campaigns. Armyworm monitoring system During the period of March- April 1991, outbreaks of the armyworms were reported from a number of places on both Unguja and Pemba Island. As a result, the Plant Protection Division -Zanzibar approached then the Ministry of Agriculture and Food Security in Tanzania Mainland and asked for the assistance of Pest Control Services (PCS) -Tengeru in establishing a system for monitoring and control in Zanzibar. In response to that, the Armyworm Co-odinator from PCS–Tengeru visited Zanzibar in July 1991. Following this, a number of steps were taken aimed at establishing the armywom monitoring system, which include appointment of a national co-odinator based at Kizimbani Agricultural Research and set up a network of pheromone traps. This system worked well in the early years of its establishment. Currently the monitoring system of armyworm is non-functional due to a number of logistic constraints. Therefore there is an urgent need for improvement of the system. Rodents In Zanzibar, rodent infestation is restricted and universal problem of coral rag areas. This is mainly contributed by farming patterns being practised on the coral rag zone. According to Borsa (1987), the cultivation of coral rag plots is normally done in a shifting system, whereby a piece a land is cultivated after the bush is cleared and burnt. The main infestation occurs during Masika and Vuli seasons, and the rodents affect the planted seeds. This kind of damage forced farmers to replant several times. Rodents also cause damage before and after harvest in crops like cassava, sweet potatoes, maize and pigeon peas. Very often rodent infestation is found in the homes. The most common species which cause damage in agriculture activity are: Rattus norvegicus (Norway rat) Mus musculus (House mouse) Rattus exulans (Polynesian rat) Cricetomys gambianus (Giant rat, in Swahili known as Panya Buku) There are two methods of controlling rodents. Physical or mechanical methods. Chemical methods.
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