Source: Munthali et al. 1990.
Source: Munthali et al. 1990.
Many other species of grasshoppers and crickets (Order: Orthoptera) occasionally feed on cotton, but do not normally cause extensive damage to the crop - although in certain years they may occur in such large numbers that they inflict local damage that can be quite serious, or even total. These include the following species:
Gryllotalpa africana Gryllus bimaculatus Brachytrypes membranaceus Enyaliopsis petersi Cymatomera sp Homorocoryphus vicinus Pseudorhynchus pungens Nomadacris septemfasciata Acanthacris ruficornis Ornithacris (orientalis) cyanea Ornithacris magnifica Cyrtacanthacris aeruginosa Phymateus viridipes Acrida sulphuripennis Acrotylus patruelis
Harvester Termite, Nthusi (Hodotermes mossambicus) (Family: Hodotermidae). Although Sweeney suggests that there is no local name for this termite, apart from chiswe, it is often described as nthusi or nthedza. It is generally absent from the Shire Highlands, but common in all cotton-growing areas. Other termites might attack cotton, but this species is certainly the most important, causing serious damage to young cotton plants, especially during a dry spell. Damage may be so severe as to warrant, Julian Mchowa informed me, the complete replanting of the cotton crop.
Cotton Stainer, Cham'Matowo (Dysdercus spp.) (Family: Pyrr-hocoridae). There are three forms of cotton stainer that are common in Malawi, which to an ordinary person look very similar. The species involved are Dysdercus intermedius (which I found to be common at Kapalasa), Dysdercus fasciatus and Dysdercus nigrofasciatus. Given their association with the mtowo shrub (Azanza garckeana), they take the common name cham'matowo or kamatowo. But the bugs are found on many other plants, including the boabab, mlambe (Adansonia digitata), the ngoza (Sterculia appendiculata) and many species of Hibiscus. The cotton stainer feeds on the green boll, and thereby introduces a fungus disease (Nematospora) that causes serious yellowish discoloration of the cotton - hence its common name. It is found in the cotton fields near the southern Lakeshore in May. Sweeney recommended many different strategies to control the cotton stainer - encouraging insect predators, such as the assassin bug Phonoctonus nigrofasciatus, which mimics the stainer; keeping cotton away from alternative host plants and destroying these if necessary; making traps for the bugs using ngoza and njale seeds; clean weeding of the crop; hand-picking; and the use of insecticides - at the end of the colonial period DDT was the recommended chemical control (Sweeney 1961-3: 3-10). What was more controversial was the suggestion of destroying mgoza trees in the attempt to control the cotton stainer - in one experimental area near Sorgin, 4,000 trees were destroyed, but the experiment proved to be inconclusive. At the present time spraying the crop with Carbaryl is recommended by the Ministry of Agriculture. Sweeney used the term nkhunguni za thonje (cotton bug) to describe the cotton stainer, but the name seems to have been his own invention - nkhunguni is the common name of the green shield bug (Nezara robusta).
The cotton stainer can also be a pest on Macadamia, especially when these trees are grown at the lower altitudes.
Jassid, Majasidi, (Empoasca fascialis) (Family: Jassidae). The cotton jassid is a 'leaf hopper', a tiny yellowish-green insect that is found on the leaves of the cotton plant, its nymphs often resembling aphids. It feeds on a variety of plants, and like the cotton stainer is particularly associated with the Malvaceae family. It is generally found on the underside of the leaves feeding on the plant juices, and causes the yellowing or slight curling of the leaves. The jassid may do a lot of damage to young cotton, and reaches its peak population around April. Cotton varieties vary in their resistance to jassid attack, but none are completely resistant (Sweeney 1961: 10-12).
Four other bugs are often noted as occasional pests on cotton. These are: the green shield bug (Nezara viridula), which is a cosmopolitan pest occurring on many crops; the bow-legged bug, nandoli (Anoplocnemis curvipes); the iridescent cotton bug Calidea dregii, which is a bright, shiny blue insect; and the cotton aphid, nsabwe zo m 'thonje, ('lice of cotton') (Aphis gossypii), which feeds on the tips of young shoots and the leaves of the plant. When infestation is severe it turns the leaves yellow.
But, as a general rule, these four bugs occur in small numbers, and are of no serious economic importance.
Black Boll Beetle, Bingiza (Diplognatha gagates) (Family: Cetoniidae). This is a large black beetle (HB 24 mm), given the name bingiza by Sweeney, which feeds on the green bolls of the cotton. It often creates a lot of white frash as it feeds its way into the boll. Only a few bolls tend to be damaged in a garden, and it is usually noted only in the months May-June. It feeds on many other kinds of fruit (Sweeney 1964a: 35).
As was noted above, 141 species of beetles have been recorded as causing some damage to cotton, but only two other species have been noted as particularly troublesome, both of them weevils (family: Curculionidae). These are:
• Alcidodes brevirocostris, a small black snouted beetles (HB 9 mm), which feeds on the bark of the cotton plant, leaving a typical ring of frayed fibres around the stem. The plant may then die, or become susceptible to attacks by termites.
• Microcerus spiniger is a dark brown, warty, terrestrial weevil lacking wings (HB 27 mm), the larva of which feeds on the root stems of the cotton just below the soil surface. The adults feed on the leaves of the cotton. Along with termites, this was a major pest of cotton recorded by the soil pests project (1990-2), some 4-9 per cent of plants in the Lower Shire, it was noted, being attacked by this weevil (Munthali et al. 1992: 94). As this weevil feigns death, it is often described as kafadala.
Red Bollworm, Mbozi Yo Fiira (Diparopsis castanea) (Family: Noctuidae). The red bollworm, the larva of a small moth, is greyish with characteristic rose-red markings and a black head (HB 27 mm). Sweeney (1964a: 38) described it as the 'worst enemy' that the cotton farmer has in Malawi - although the red bollworm feeds only on the cotton plant. Indeed, in the first annual report of the government entomologist (1913) it was suggested that it was 'undoubtedly the most destructive insect' in the country. After hatching, the larva bores into the boll of the cotton, and seems to spend all its life right inside the boll, feeding on the flowers. The larva pupates in the ground. Although the larva damages a minimum number of bolls, it is thus difficult to control with insecticides. Even so, the ministry of agriculture recommends control by spraying with Carbaryl. The most important control measure, however, was that first suggested by Colin Smee, and practised - indeed, attempts were made to enforce the practice - throughout the colonial period, namely to have a closed season of two months, involving the uprooting and burning of all cotton plants by the end of July. In the years prior to the Second World War there was considerable debate and dispute as to whether the enforced close season and the uprooting and burning of the cotton was indeed having any real effect in controlling the red bollworm as a pest (MNA/51/189/38). Smee also noted the potential importance of two parasitic wasps that are associated with the red bollworm as control agents (1940: 13).
What was evident, however, is that, throughout the colonial period, losses of cotton crop due to the red bollworm were extremely high, often around 40 per cent of the potential crop. Smee noted that the 1922-3 season was exceptionally bad for bollworm, and on many estates crops were 'practically ruined by this pest' (MNA/Ann. Rept. Dept. Agr. 1924).
Even today, bollworm attacks continue to be the most important constraints on cotton production, and applications of pyrethroid insecti-cids to control the bollworms seems to have led to an increase in white fly (Ritchie and Muyaso 2000: 48)
Spiny Bollworm, Mbozi ya Minga-Minga (Earias biplaga) (Family: Noctuidae). Along with those of the related species Earias insulana, the larvae have varying colours, mainly brown or greyish, and are characterized by long spine-like hairs on the body. Although not as troublesome as the red bollworm, they are always present in the cotton crop to some extent. The larvae attack the flower buds and the bolls, but unlike the red bollworm they move about a great deal, and may feed on many buds and bolls. They are also associated with many plants of the Malvaceae family, to which of course the cotton plant belongs.
Pink Bollworm, Mbozi ya Pinki (Pectinophora gossypiella) (Family: Noctuidae). As its common name suggests, the larva of this moth when fully grown (HB 13 mm) is of a pinkish coloration. First recorded in Malawi in 1925, it was not until the outbreak of the Second World War that it was noted as common in the Southern region, but even then it was not considered as serious a pest as the red bollworm. It attacks flower buds and the green bolls of the cotton, and is mostly in evidence in May and June, when most of the damage is done. It has been suggested that the uprooting and burning of the cotton at the end of the season tended to keep this pest in check during the colonial period; but it is still considered a serious pest of cotton. As it tends to keep within the boll, spraying with insecticides such as Carbaryl is said to be only slightly effective against it (Sweeney 1962: 26-7).
In the years immediately after independence, pink bollworm became a serious pest in the Lower Shire Valley, and efforts were made to curb the outbreak. Two strategies were employed: a close season of 2-3 months and a re-emphasis on the uprooting and burning of the previous year's cotton plants; and the fumigation of all cotton seed with methyl bromide (BRS/A17A).
African Bollworm, Mbozi ya Chifilika, (Helicoverpa armigera) (Family: Noctuidae)
Originally placed in the genus Heliothis, the larva of this moth, the largest of the bollworms, goes under several common names - American boll-worm, cobworm (on maize), or budworm (on tobacco). Although it is one of the worst pests of cotton in the United States, it is in fact a cosmopolitan species, and is a serious pest on a variety of different crops - especially maize, groundnuts, tobacco, tomatoes and cotton. Sweeney suggests that it may have been of Asiatic origin (1962: 14-16). The larva is greenish-yellow to pale brown, with characteristic black and white stripes along the sides of the body (HB 35 mm). It feeds on the buds, flowers and bolls of the cotton, and although not generally considered a serious pest, often appears suddenly in great numbers, and can thus, locally, cause extensive damage to the crop. It tends to be less serious on cotton than on maize. Ministry of Agriculture recommendations for the chemical control of this pest in the past have included DDT, and now include Carbaryl or endosulfan.
Vegetable gardens in low-lying areas (dambo) or near streams - enabling crops to be irrigated - have always been an important part of people's livelihood in rural areas. Many of my elderly women friends in the Domasi valley had their dimba gardens for growing vegetables - groundnuts, cabbage, tomatoes, onions, beans - that they utilized as food, as well as selling in Songani market in order to generate the cash necessary to buy their basic household requirements. Over the past three decades, in order to provision a growing urban population, the production and marketing of dimba vegetables have become important occupations for many Malawians. The Integrated Pest Management project (1996-2000) made a particular study of dimba crops, and they estimated that 33 per cent of households in the Blantyre district had access to dimba land and grew dimba crops, and around 21 per cent used pesticides. The two important dimba crops are tomato and cabbage.
Tomato, Matimati, (Lycopersicon esculentum). A native of South America, the tomato is an extremely important crop to Malawians, and is grown in semi-wild kitchen gardens within the village environs (along with chillies, tsobola (Capsicum annuum) and spinach, bonongwe (Amaranthus sp.)), on termite mounds, and in dimba gardens. They are seldom eaten raw, but are used as an essential ingredient in relish (ndiwo) dishes. Although tomatoes are occasionally attacked by the African boll-worm (Helicoverpa armigera), the larvae of the semi-looper caterpillar (Plusia sp.) and the green shield bug (Nezara viridula), the primary pest on tomato is the red spider mite (Tetranychus evansi). This mite has been a serious pest in southern Africa since the early 1980s, and first appeared in Malawi in 1993. Two years later it had spread throughout the country, and is now present and a troublesome pest in all tomato-growing areas. It has been given the name stoniwashi, because it appeared, I'm told, around the same time as a particular brand of men's jeans that had a mottled appearance. The red spider mite attacks a wide range of crops besides the tomato - beans, sweet potatoes, peppers, citrus, coffee and tea. It feeds on the sap of the tomato leaf, initially giving rise to a yellow mottling; but the leaves then turn bronze and are shed, and the plant may eventually die. The mites themselves are tiny, of variable colour, but often red. They appear mainly during the dry season, from August to November. Much research has recently been undertaken to develop an integrated strategy of pest control in relation to the red spider mite. These measures include crop rotation, the uprooting and burning of infested plants, the use of botanical insecticides that have long been used in Malawi - for example, infusions of the tobacco plant, or of such shrubs as mphanjobvu (Neoravtanemia mitis) and ombwe (Tephrosia vugelii); interplanting with aromatic herbs such as mpungabwe (Ocimum canum); increasing the humidity near the tomato plants by mulching or close planting; the development of resistant varieties of tomato; and the use of insecticides such as Dimethoate (Chongwe 1999; Mtambo 1999).
Cabbage, Kabichi, (Brassica oleracea). Cabbages are grown in dimba gardens particularly at the higher altitudes; but, whereas tomatoes tend to be a dry season crop, cabbages are mainly grown during the rainy season. Along with related members of the genus - Chinese cabbage, tanaposi (Brassica chinensis) and rape, mpiri wotuwa (Brassica napus) - the cabbage is prone to a wide variety of insect pests. These include the shield bug Bagrada hilaris, a small yellow and black insect that may be numerous in hot dry weather; the mealy cabbage aphis Brevicoryne bras-sicae, which is wax-covered and infests the heart of the cabbage; and the larvae of the diamond-back moth, Plutella xylostella. It is this latter pest that has been the subject of attention and research in recent years.
The adult diamond-back moth is a small grey moth with a wingspan of about 15 mm, and a characteristic diamond pattern on its back, noticeable when the wings are closed at rest. Hence its common name. The larvae are pale green (HB 12 mm), and active, and when disturbed suspend themselves by means of a silken thread. The larvae feed on the leaves of the cabbage plant from the underside, making hundreds of holes that reduce the leaves to a lace-like condition. The moth has a cosmopolitan distribution, and is a serious and widespread pest of cabbage. Harriet Thindwa suggests that the diamond-back moth has become a 'major setback' to the growing of cabbages in Malawi, as it has now become resistant to many brands of insecticide. Thus experiments are now being conducted to find alternative strategies to control this pest. These include biological control, utilizing two parasitic wasps, or the microbial pesticide Bacillus thuringiensis; and using botanical insecticides, such as an infusion of the leaves and seed of the neem tree (Azadirachta indica) or of the wayside shrubby herb Tithonia diversifolia. Without control it is estimated that as much as 50 per cent of the cabbage crop may be lost (Thindwa 1999b; Mtambo et al. 2000).
The diamond-back moth is particularly noticeable during the dry season, from July to October. Local people simply refer to the larva of the diamond-back moth as mbozi (caterpillar), and one of the main forms of control used by local people is the insecticide Carbaryl. It is simply put into a watering can and poured over the cabbages. Stephen Carr (2001) suggested to me that lemon grass, cut and put over the cabbage, is a useful insect repellent, as the moth dislikes its smell. Research studies have shown that insecticides are commonly used by a few smallholders growing tomato and cabbage, and these include organophosphates such as Temik, Lanate and Actellic; synthetic pyrethroids, such as Ripcord and Sherpa, and the well-known carbamate Sevin. Farmers often mix different insecticides - as herbalists combine different roots, as it is thought that this gives them extra strength, and often use concentrations way above those recommended. Many of the insecticides bought at market stalls are obsolete or out-of-date, and several of the insecticides, e.g.
Temik and Lanate, are in the 'extremely dangerous' category. Interestingly, however, few farmers growing cabbage and tomato considered insect pests to be a problem - of more concern to them were the high costs of fertilizer, high transport costs and low prices for vegetables (Ritchie and Muyaso 2000: 2/174-83).
Although many crops are grown in the estate sector, including for example maize, sunflower, citrus, soybean, macadamia and groundnuts, I shall here focus on the insect pests that are associated with the four crops that constitute the primary agricultural exports: tea, coffee, tobacco and sugar.
Tea (Camellia sinensis,)
Tea is second only to tobacco as an important source of foreign exchange in Malawi, and the total area under tea now stands at around 39,800 ha. Established at the end of the nineteenth century, tea production is mainly focused in the Thyolo and Mulanje districts, and employs over 42,000 people. During the colonial period tea was entirely produced by private estates, usually owned by small European companies, but in 1967 the Smallholder Tea Authority was established, under Roger Royle, to enable local farmers to grow tea. Royle was an experienced agriculturist who had earlier won renown for his support of soil conservation as against biblical fundamentalism (cf. Chakanza 1998: 77-81). At the present time there are around 5,000 local growers in the Thyolo and Mulanje districts, with an average holding of around 0.5 ha per smallholder, amounting to around 2,500 ha in total (TAM 1991). Although, like any other agricultural crop, tea is exposed to many insect pests, what I always found surprising, having worked for over seven years as a tea planter in Malawi, is that the tea bush is relatively free of pests. Indeed, when I discussed tea pests with Alexander Boatman on the slopes of Thyolo Mountain, where he has worked as an instructor for the Smallholder Tea Authority for some thirty years, he was adamant that local growers are not unduly worried about insect pests. This was confirmed in my discussions with Pritam Rattan, a research scholar who is an acknowledged authority on the pests and diseases of tea in Africa. Rattan suggested to me that only three pests have salience in Malawi - thrips, red spider mite and mosquito bug - and none of them constituted a real problem. As the loss of crop through these pests is negligible, he did not think the loss worth the high costs of spraying with insecticides. Even so, some estate managers for 'cosmetic' reasons do use insecticides: Rattan felt that these were not usually cost-effective. It is significant, then, that in his paper on pest and disease control in Africa with respect to tea Rattan should write: 'Surprisingly though, tea in many countries of Africa is almost free from serious pests and diseases' (1992: 331).
But with new cultural practices and with larger areas being planted with vegetatively propagated material, this situation, he noted, may well change. However, it is worth noting that an advertisement in the Tea Planter's Handbook (Grice 1990:68) relating to pest control reads: 'Tea planters can lose up to 40% of potential yields through the ravages of insects and pests such as mosquito bug (Heliopeltis), thrips and red spider mite.' This seems to be something of an exaggeration.
I will, then, outline briefly the six main pests of tea, keeping this proviso in mind.
Mosquito Bug (Heliopeltis schoutedeni) (Family: Miridae). The mosquito bug is one of the most important pests of tea, as well as being a pest on many other crops, including cassava, groundnuts, cotton, pigeonpea, beans, coffee and many wild plants. It was first recorded in Malawi in the 1920s, and is a true capsid bug. It is bright red and black (HB 10 mm), with long black antennae, and though active it is rarely seen, as it is crepuscular in habits and keeps hidden.
Both nymphs and adults feed by piercing the plant tissues - tender stems, shoots, young leaves and buds - with their proboscis and sucking the sap. The saliva seems to be toxic, and this causes the blackening and withering of the leaves. In severe cases the bush looks scorched, and there may be severe loss of the crop. Although breeding for most of the year it is scarce during the dry season (September-November) and reaches its peak population at the end of the rains, April-May. It can cause serious damage to young tea in nurseries. The insecticide Endosulfan is considered to be the most effective form of control (Sweeney 1965).
Red Spider Mite (Oligonychus coffeae) (Order: Acarina). The red spider mite is a common pest of tea - this particular mite shares the same name as the tomato pest - and, although present throughout the year, it is mainly found during the dry season from September to December. Its numbers decrease during the rains. A tiny mite, bright crimson, and elliptical in shape, it feeds mainly on the sap of mature leaves, which, if the infestation is severe, can turn a reddish or coppery colour. The leaves then wither and drop off. As with the mosquito bug, the local jat seems more susceptible to the mite than the Indian hybrid tea. There seems evidence that they tend to attack weak and unhealthy tea bushes, and so cultural practices, such as clean weeding, mulching and an adequate level of fertilizer, which increase the vigour of the bush, tend to reduce the severity of attack by the red spider mite. Although this pest may cause loss of crop, Pritam Rattan fervently believes, from experimental evidence, that the use of chemical pesticides to control the red spider mite had not led to any increase in yield, and was hardly cost-effective given the high cost of spraying. As with the mosquito bug, the red spider mite is mostly unrecognized by smallholder tea growers. Judging from early reports, the red spider mite was considered a troublesome pest during the 1920s; and often did 'considerable damage'. Applications of lime sulphur were then used as a control measure (Smee, Ann. Rept. Dept. Agr. 1927: 15; Rattan 1992: 337).
Tea Thrips (Scirtothrips aurantii) (Order: Thysanoptera). Thrips are ubiquitous in Southern Africa and a pest on a variety of crops - tobacco, citrus, tomatoes, and macadamia, as well as tea. They are tiny delicate insects, orange-yellow, 1-2 mm long, with membraneous wings, and are good fliers. They occur throughout the year, but are commonest during the dry season, September to December, the nymphs and adults feeding on the tender parts of the tea - young buds, leaves and tender shoots. This causes the margins of the leaves to become brown and brittle, and if infestation is severe defoliation occurs, leaving leafless stems. The time of pruning the tea seems to have a significant effect on the local control of the thrips, and applications of insecticides such as Fenitrothion and Malathion are recommended by the tea research foundation (Grice 1990).
Carpenter Moth (Teregra quadrangular) (Family: Arbelidae). On my visits to Zoa and to the tea estates in Mulanje I often encountered the occasional tea bush that had been damaged by the larvae of the carpenter moth. The presence of these brown caterpillars (HB 20 mm) is noticeable by a web that each caterpillar spins, although being nocturnal they are rarely seen. Although not a problem on mature tea, the caterpillars of the moth can ring-bark the stems of young tea, which may result in the death of the plant. Carbaryl is seen as an effective insecticide by the research foundation, to be applied in July and August. Problems with the carpenter moth have only been evident in the last twenty years or so (Grice 1990).
Gelatine Grub (Niphadolepsis alianta) (Family: Limacodidae). In May 1938 there was a serious outbreak of what became known as the 'gelatine grub' on two tea estates in the Thyolo district. It suddenly appeared in 'colossal numbers', was extremely destructive of the tea, and caused extreme consternation among European tea planters (Smee 1939). It was not heard of again until the 1960s, when high local populations occurred in both the Thyolo and Mulanje districts. Since then the gelatine grub has been a continuous presence on tea estates, without ever becoming a serious pest. The 'grub' is the caterpillar of a small moth, and is rather slug-like. It is a characteristic bluish-green, with longitudinal wavy white lines (HB 10-15 mm), and rather sticky to the touch. The caterpillars normally feed on the mature leaves of the tea bush, and under favourable conditions can occur in large numbers and do considerable damage. Around 500 caterpillars have been counted on one bush. But normally they are not considered a serious pest (Grice 1990).
The allied nettle grub (Parasa vivida), a colourful caterpillar with stinging hairs, is also a pest on tea, and can be troublesome to tea pickers. Its local name is chiyabwe.
Bagworm, Mtemankhuni (Eumetia cervina syn. Clania moddermanni) (Family: Psychidae). Various species of bagworms have been recorded from tea, the most noticeable being Eumetia cervina. They are well-known caterpillars of moths, which construct a portable home for themselves from bits of twigs, thorns, sand, and leaves, binding the 'bag' together with silk. The caterpillars can be quite active insects, freely moving about the bushes. Colin Smee (1945) long ago in an article on bagworms in tea recorded four essential kinds in relation to the type of bag constructed - pagoda, straight stick, conical silk bag, and criss-cross grass stalk types. What prompted the article is that there had been reports of serious outbreaks of bagworm in tea, especially in the Thyolo area, which had caused considerable damage locally. At the present time they are not a serious pest of tea, although they may do occasional damage; but according to the research foundation they are easily controlled by insecticides (Grice 1990).
The Tea Planter's Handbook records several other insect pests on tea, the leaf weevil (Systates smeei), white grubs, the elegant grasshopper, aphids and various mites; but only termites seem to be serious pests, as they are prone to ring-bark young tea (Grice 1990). One tea planter suggested to me that only three pests gave him undue concern - mosquito bug, carpenter moth and termites - but even these were not unduly serious. Many planters have suggested that boron is a simple and effective pesticide against termites.
Coffee (Coffea arabica)
In contrast to tea, which seems to have few serious pests, coffee, like cotton, seems to be besieged with insect pests and diseases. Walking through a tea garden one really has to search hard even to find an insect pest, apart from the odd termite or mosquito bug. Yet on an instructive tour of Nsuwadzi coffee research station in Mulanje with James Biscoe in May 2001, I was shown around a dozen insect pests - and these were not unkempt coffee gardens. Indeed, tea as a crop in Malawi owes its origins at the end of the nineteenth century to the fact that the coffee estates in Mulanje all failed - largely owing to losses from pests and diseases. Coffee still tends to be a subsidiary crop on estates, and the present area under coffee is around 5,000 ha, only a fraction of the land under tobacco and tea, although there has been some expansion in recent years with improved irrigation and concerns over tobacco prices. But, as Colin Smee suggested long ago, although coffee is a very hardy plant it suffers from a large variety of insect pests, practically all through the year, particularly during the flowering season. Coffee prefers slightly humid conditions, and in Malawi it is grown mainly on estates at a height of between 500 and 1,250 m. Among the more significant pests of coffee are the following four species:
Coffee Stem Borer (Anthores leuconotus syn. Monochamus raspatory (Family: Ceramycidae). The stem borer does a considerable amount of damage to coffee. The adult beetle is large and pale grey, with dark greyish-brown bands (HB 30 mm), with extremely long antennae, 70 mm long. This longicorn beetle is common throughout Malawi, especially in the early rains, and it lays its eggs under the bark of the coffee tree. The larvae, described by local people as mbozi, bores into the stem of the Coffee, and makes its way down, and then back up the stem, leaving a lot of wood frass at the base of the tree. The stem of the coffee may become riddled with tunnels. The grub eventually pupates in a large cavity within the stem. The coffee plant begins to show the effects of this damage during the dry season, when the leaves begin to turn yellow, wither and are shed. Smee described this beetle as undoubtedly responsible for more damage to coffee than any other insect, and during the colonial period zinc sulphate and lead arsenate were used as control measures (MNA/Ann. Rept. Dept. Agr. 1927:18). According to James Biscoe it was the coffee stem borer that wiped out the whole coffee industry in Mulanje at the end of the nineteenth century. Control measures now include the use of such insecticides as Regent or Parathion, or having children collect the stem-borers (Clowes et al. 1989).
Antestia Bug, Nkhunguni (Antestiopsis lineaticollis) (Family: Penta-tomidae). During the colonial period this shield bug was described as the 'Cameron bug', and was recorded as a common pest on coffee, although the damage done was varied and irregular - as the abundance of the insect fluctuated from year to year. The adult is shield-shaped and dark brown, with orange spots and markings (HB 10 mm). It keeps to dense foliage, out of the sun, and is thus rarely seen. It sucks the fruit of the coffee, and can cause considerable damage to the berries, as well as introducing bacteria into the fruit. Insecticides are the recommended control, such as Fenitrothion and Parathion (Clowes et al. 1989).
Dusky Surface Beetle (Gonocephalum simplex) (Family: Tenebrionidae). These are small beetles, the larvae of which are described as 'false wireworms', which lie hidden in mulch and debris during the day. At night they emerge and feed on the stems of the coffee plant at ground level, often ring-barking the plants. Although not usually a problem, in some areas, such as on estates in the Namweras, they can be an acute problem, killing many young coffee plants. It has been suggested to me that where the herb Arachnis pintoyi, which is allied to the groundnut, is grown between the rows of coffee, there is little trouble with the dusky surface beetle (Biscoe 2001).
Leaf Miner (Leucoptera meyricki) (Family: Lyonetiidae). This is the caterpillar of a small white moth that feeds on the underside of the leaves, and can cause considerable damage to coffee, leading to severe defoliation. It is described as the most important pest of coffee.
The caterpillar of a similar moth, aptly described as a 'leaf-skele-tonizer' (Leucoplema dohertyi) is also a problem on coffee, and in recent years serious outbreaks have occurred. To control these caterpillars, chemical insecticides such as Parathion and Fenitrothion are recommended by the research foundation (Clowes et al. 1989).
Around thirty other species of insects are described as pests of coffee, but undoubtedly the most problematic pests are two pathogenic fungi -the coffee berry disease (Colletotrichum coffeanum) and the bark disease (Fusarium lateritium) - the latter having almost wiped out the coffee industry in Malawi in the 1950s (Clowes et al. 1989). One of my Malawian friends always referred to these diseases as 'leaf lust'.
Tobacco, Fodya (Nicotiana tabacum)
An annual crop, and originally a native of tropical America, tobacco is the primary cash crop of Malawi, and is grown both on estates and by smallholder farmers. Tobacco has been grown in Central Africa since time immemorial, but the growing of Virginia tobacco on a commercial scale was pioneered by John Buchanan at the end of the nineteenth century. Since the 1970s production of tobacco in Malawi has more than doubled - an area of 113,000 ha is now under tobacco - and, as noted earlier, it now accounts for over 70 per cent of the country's foreign exchange earnings. Malawi, in fact, is the world's largest exporter of burley tobacco, and produces more than 120 million kg of tobacco, almost all of which is exported (Matthews and Wilshaw 1992). Most of the tobacco now grown in Malawi is either flue-cured Virginia or burley tobacco - the latter being air-cured by hanging it on racks in grass-thatched sheds. Significantly, tobacco is seen as a 'man's crop', even though women make up nearly 70 per cent of all full-time farmers in Malawi. Malawi's heavy dependence on two crops, maize and tobacco, together with an external debt of around $2 billion, is having high social and environmental costs - accelerating degradation of the land through deforestation, loss of soil fertility, depletion of water resources, and high levels of poverty among the rural population.
It is of interest that the Malawi Tobacco Handbook (Matthews and Wilshaw 1992) makes no mention at all of insect pests on tobacco - apart from an advert by the company 'Antipest'. Yet throughout the colonial period insect pests were viewed by planters as a serious problem, particularly the white fly (Bemisia tabaci), which transmits a disease locally known as 'leaf cure' or 'cabbaging', and the tobacco beetle. The latter species attacks the stored tobacco (MNA/A3/2/267). Discussions I had with local farmers and farm managers in the Namadzi area, together with my own observations, suggests that five species were particularly troublesome on tobacco. These were the following.
Common Black Ant, Nyerere (Pheidole spp.) (sub-family: Myrmecinae). These ants are prolific everywhere, even entering houses, and have a particular fondness for the tobacco seed. They can therefore cause problems in tobacco nurseries. The activities of these ants are confined to seed beds; but owing to their ubiquity the ants are capable of removing much seed, so that germination is practically negligible.
African Bollworm (Helicoverpa armigera) (Family: Noctuidae). Known to European tobacco farmers as the 'tobacco budworm' and to local people as mbozi or chipukwa, this caterpillar is a common pest on tobacco. It is usually pale green, with white and black mid-dorsal stripes, and is around 38 mm long. As was noted earlier, it is a cosmopolitan species, and is also a common pest on maize, cotton and groundnuts. It bores into the stem of the tobacco plant, and on tobacco farms near Namadzi it was noted on young tobacco in December and January. One farm manager told me that he had used Tamaron as an insecticide without success, and had then had to use Karate. Only a few kilometres away another tobacco farmer told me he had not been troubled with tobacco
'budworm' that year (2000-1), so that attacks by this pest may be quite local.
Elegant Grasshopper, M'Nunkhadala (Zonocerus elegans) (Family: Pyrgomorphidae). A common pest on both maize and cotton, as noted earlier, the elegant grasshopper is also a pest on tobacco. As it also feeds on a wide variety of other crops, this insect is probably the most troublesome, as well as the best-known, of all Malawian agricultural pests. The recommended insecticide is Baythroid (a synthetic Pyrethroid) or Malathion.
Tobacco Aphid, Nsabwe (Myzus persicae) (Family: Aphididae). This aphid feeds on a variety of plants, and in some years can be abundant on tobacco. It is less a problem in itself, than as a vector for various virus diseases that affect tobacco.
Green Shield Bug, Nkhunguni (Nezara viridula) (Family: Pentatomidae). This is a small green shield bug, with a strong, somewhat unpleasant smell. It is smaller than Nezara robusta (which is eaten) (HB 18 mm), but is much more widely distributed, and is common everywhere, attacking a variety of plants - beans, cotton, and macadamia, as well as tobacco. As with other tobacco pests, the commonest form of control seems to be the application of chemical insecticides, such as Bathyroid or Tamaron. In the Neno district I found this bug to be a very troublesome pest on the fruit of macadamia trees.
These five pests were those discussed by local farmers, and familiar to me on the tobacco farms of the Namadzi area. But many other insect pests have been recorded on tobacco, including cutworms (Agrotis sp.), white grub (the larvae of Scarabeid beetles), the giant cricket (Brachytrypes membranaceus), the red spider mite (Tetranychus sp.) and the larvae of several moths. Yet the insect that was most discussed during the colonial period was the tobacco beetle, Lasioderma serricorne. This is a tiny reddish-brown beetle (HB 2-4 mm) that feeds on stored tobacco, as well as on other stored products, and can cause serious losses. Sweeney records that it was often found living in pyrethrum powder, an insecticide often used to kill it! (1962: 12). In the past, infestations of these beetles were so alarming, that the agricultural department often decreed the destruction of several tons of tobacco in order to eradicate the beetle or to prevent its spreading. As now, the main form of control was by fumigation. Smee argued that all tobacco should be uprooted and destroyed at the end of the season in order to control insect pests (MNA/A3/2/254).
This practice, however, does not seem to be carried out at the present time - for the dried stems of the tobacco plant are collected by women as fuel.
Sugarcane, Mzimbe (Saccharum officinarum). Although sugarcane is grown all over the country on a small scale, usually in low-lying and dambo areas, and is chewed raw by almost everyone for its juice, as a cash crop it is confined to the larger estates. These are located mainly at Dwangwa on the Lakeshore north of Nkhotakota, and at Nchalo in the Lower Shire Valley. Around 19,000 ha of land are under sugarcane production.
Around a dozen insects have been recorded as pests on sugarcane, but surprisingly, compared with Zimbabwe and Mozambique, Malawi has few serious pests. When I discussed insect pests of sugarcane with one estate manager, he suggested to me that there was no real problem with insect pests in the Lower Shire Valley, and if outbreaks did occur they were usually local, and too late to do anything about. When I explored the cane fields at Nchalo Sugar Estate with Henry Moyo, who was responsible for pests and disease control, apart from slight damage from the pink stalk borer, and the occasional termite and elegant grasshopper, we found little evidence of any insect damage. Indeed, Moyo suggested to me that the main problems of sugarcane focused around rodent damage, especially by the cane rat (nchenzi) and rust (fungal) disease, rather than insects. The three insects that have caused acute problems elsewhere in Southern Africa - the black maize beetle (Heteronychus licas) - both the adult and larvae ('white grub') damage the cane; the larvae of the moth Eldana saccharina; and the sugarcane borer, Chilo sacchariphagus - have not been recorded as causing problems on the sugar estates of the Lower Shire Valley.
Besides termites, the elegant grasshopper and the mealy bug (Saccharicoccus sacchari), and the occasional outbreak of locusts - there was a serious influx of locusts in February 1993 - only the pink stalk borer Sesamia calamistis (family: Noctuidae) seems to be a serious pest on sugarcane at Nchalo. The larvae are pink to violet, with a brown head (HB 30 mm) and they burrow into the stem of the sugarcane, and feed on the inner pith. They can thus do considerable damage to the cane.
(On the insect pests of sugarcane see Clowes and Breakwell 1998: 213-28.)
I have discussed above many of the insect pests that damage the main crops of Malawi, in both the smallholder and estate sectors of the economy. There is no doubt that insects in Malawi take a high toll of agricultural production, and perhaps around 10-20 per cent of the main subsistence crops, such as maize, beans and pigeonpea, may be lost to insects. Yet there is also a growing sense in Malawi, as in other parts of the world, that a 'war against nature', which is reflected in an undue reliance on chemical pesticides, is damaging both to ourselves and to the natural world. Yet little more than a decade ago one Malawian scholar was writing: 'Today, agricultural fields are real battle-fields. Anything wanting to grow, creep or fly on the farmlands is inevitably caught in the firing line of chemicals and perishes in it.' And he notes how excessively chemical pesticides have been used in Malawi given their low cost, effectiveness and availability (Manda 1985: 31).
However, the pious platitudes put out by the World Bank and development agencies, namely that a society is only viable and sustainable if both human well-being and the ecosystem are maintained or improved (has anyone ever argued otherwise?) seem increasingly to be unduly compromised by the widespread use of chemical pesticides. Nowadays, these are not only expensive, but are seen as dangerous to human health, and ecologically suspect. Yet our dependence and commitment to pesticides is quite staggering, even though they have led to serious health problems -besides causing asthma, cancer, infertility and chronic fatigue and mood disorders, there are many thousands of fatalities each year from the use of pesticides - as well as to high ecological costs, such as the loss of wildlife, pollution of groundwater, and the elimination of beneficial insects. Rachel Carson's classic study Silent Spring highlighted the problematic nature of synthetic pesticides many years ago, although she was not against chemical insecticides per se (1962: 11), but only called for a more balanced ecological approach, so that we could find a way both to manage insect pests, and also to protect ourselves and the environment. But the emphasis on the control of insects through pesticides has created two additional problems. Firstly, the insects themselves have become resistant to the pesticides and so we have created a 'quickening treadmill', with the need for ever-increasing use of ever more powerful pesticides. And secondly, the pursuit of biologically based methods of pest control has tended to be hampered by our commitment to pesticides (Winston 1997: 12-16).
Nonetheless, as we have noted above, the emphasis in Malawi over the last decade has been to encourage integrated pest management - if for no other reason than the fact that ordinary farmers in Malawi can no longer afford the high costs of insecticides. A kilogram of Carbaryl, for example, now costs around 475MK (2000), almost half the monthly income of an agricultural worker. Thus, as both Smee and Sweeney advocated many
years ago, efforts are currently being made - as reflected in the Integrated Pest Management Project (Orr et al. 2000) - to encourage non-chemical pest-management strategies. These include: crop rotation, suitable tillage practices, encouraging natural enemies and developing biological controls of the pest, the removal and burning of infested plants, selecting resistant varieties, interplanting with aromatic herbs to keep pests at bay, and the development and use of organic insecticides, such as ombwe (Tephrosia vugelii) and mphanjobvu (Neorauthanis mitis). It is thus highly ironic that tobacco farmers and tea estate managers who have for decades been avid enthusiasts for chemical pesticides (and fertilizers) should now, with the potential development of organic crops for export (such as Echinacea) have suddenly become converts to organic farming.
There is, however, still a ready market for insecticides among smallholder farmers, and in most markets in Malawi one usually finds two or three vendors selling small packets of insecticides, such as Sevin, Actellic and Temik (Figure 5). Most of these vendors are young men in their early twenties. In a survey I made of Zomba Market Sevin 85c (Seveni) was popularly sold as an insecticide, and seen as effective in protecting pumpkin, cabbage, and tobacco against such insects as grasshoppers (chitete), caterpillars (mbozi), leaf beetles (mkupe), termites (chiswe), aphids (nsabweza m'masamba, 'plant lice') and cotton stainers (chama-towo). The vendors bought the Sevin at 15MK a packet and sold it at 2MK per spoonful. The insecticide was described as medicine (mankhwala), and was clearly aimed at farmers growing cash crops in dimba gardens. The pesticide Actellic is sold everywhere, and is particularly used to combat house mites (nyakanyaka), bed bugs (nsikidzi) and the maize weevil (kafutwefutwe). One difficulty, however, is that Malawi does not manufacture any pesticides, and so the continued reliance on chemical insecticides for pest control absorbs a substantial amount of foreign exchange. (For general studies of insect pests and their control, particularly relating to Africa, see Smit 1964; Kumar 1984; Van Emden 1989; Geddes 1990; and NRI 1992).
Was this article helpful?
You Might Start Missing Your Termites After Kickin'em Out. After All, They Have Been Your Roommates For Quite A While. Enraged With How The Termites Have Eaten Up Your Antique Furniture? Can't Wait To Have Them Exterminated Completely From The Face Of The Earth? Fret Not. We Will Tell You How To Get Rid Of Them From Your House At Least. If Not From The Face The Earth.