Agriculture is the backbone and engine of growth in most African economies accounting for more than 35% of the African Growth Domestic Product (GDP), 40% of exports and over 75% employment. In Uganda, it is the biggest source of livelihood to over 90% of the Population, 95% constituted by resource-poor small-scale farmers.
While cultivation of crops and reaping high yield is the yearning of many a farmer, insect pests, low soil fertility, disease and poor agronomic practices are constraints to high agricultural production, economic development and ultimately Africa’s self sustenance.
In Uganda, local farmers practice a variety of cultural, biological and chemical methods to safeguard their crops from pests and diseases. These methods range from bush burning, long fallow periods, use of local organic matter from dead plant tissues and animal refuse, mixed cropping, weeding, use of pest predators, manipulation of planting time, the use of inorganic fertilizers and pesticides and planting selected healthy germinating seeds to protect crops from destruction.
The cultural method is one of the oldest and commonest strategies used in traditional agriculture for it is economic, dependable and widely acceptable. It entails the use of regular farm operations that are specifically designed to destroy crop pest. The method is labour intensive and easily adoptable by low resource farmers.
In the northern districts of Gulu, Kitgum and lira,in Uganda, bushes are cleared and burnt down 3-4 months prior to cultivation and left to fallow. Local manure in the form of cow dung, animal urine, wood-ash, poultry litter, dead leguminous plants, household refuse, dead plant tissues and vegetation compost are added into the field. Some farmers in central Uganda add coffee husks to the field. The burning of the fields and the long fallow periods adversely affect pest population by slowing down their rate of feeding hence reducing incidences of the pathogens surviving to the next planting season. The nitrogen in organic matter increases the fertility of the soil.
Kworora Munaabi, a farmer in western Uganda explains that they still soak seeds first, put them in sacks or polythene bags until they start to germinate, after which they are planted. This hastens seed growth before pests in the soil can affect them. Sterilized hoes are used to plant the seeds at moderate depths, facilitating fast germination and preventing seeds from consumption by birds and chicken. Weeding entails removal of unwanted foreign plants where pests survive or hide, to reduce competition for soil nutrients. Scarecrows are used to scare birds from attacking crops like maize, millet and sorghum.
Manipulation of planting time is one of the major techniques used in the country by over 60% percent of the local farmers. According to Mary Jamaro, a local farmer in Nebbi district, groundnuts and okra are healthier when planted early for they escape serious aphid vectors rampant towards the middle and end of the rainy season. Early planting of maize and sorghum prevents shoot flies and reduces problems with the leafhoppers and stalk borers. Even in cases where the pests become extensive 6-12 weeks after emergence, there is no significant reduction in the grain yields. Enyi (1974) who carried out a study in Morogoro, Tanzania concluded that early planting of cowpeas gave higher yields than late planting.
Intercropping is a cultural method involving cultivation of two or more compatible crop mixtures in the same piece of land during the same growing period. The most preferred combinations dominated by small-scale farmers in eastern and northern Uganda are mixtures of cereals with legumes like maize and beans, sorghum and millet, pigeon peas and maize, millet or sorghum. These simultaneous growing of crop mixtures have inbuilt mechanisms that lessen the gross effects of pest damage.
The biological method is an old non-costly tactic that is still used by farmers. Biotic mortality agents which include parasites and predators like insects, spiders, lizards and birds feed on the crop pests reducing their population. The use of micro-bail crop protectants play an important role in the natural regulation of populations of crop pests. Artificial increase and release of parasitoids on stem borers and legume pods lead to reduction in the population of the pest. In some cases, diseased insect pests have been successfully used to control pests. Success was attained with the use of Parasitoid apanteles against the sugarcane borer in Madagascar. In western Kenya, a 2-year study of the effect of Chillo partellus on maize and sorghum under subsistence agriculture revealed that the local predators contributed over 97% mortality of the stem borer in the age interval from egg to early instar larvae. This method is relatively cheaper but care should be taken when introducing the parasites and predators to avoid upsetting the balance by increasing pests
Chemical control involves use of insecticides to kill pathogens and reduce their potential to destroy crops. This method though effective, is toxic and harmful to human health and environment when excessively used. There is also a shortfall as far as some pests are concerned. For example, while the coffee fungus affects the coffee directly and will need to be sprayed directly, some pests hide and grow in nearby weeds from where they attack crops at the opportune moment. Continuous usage of pesticides can also lead to pest resistance and destruction of natural enemy complexes hence disrupting the natural ecosystem. The method is particularly expensive to local subsistence farmers with limited sources of income, who form the majority of agricultural practitioners in Uganda.
Most farmers agree that tapping synthetic-and sometimes dangerous-pesticides, herbicides and fertilizers can double farm productivity but the chemical fertilizers have also, in some cases, tainted produce and contaminated the ground.
However, some insecticides of plant origin can be used without the problems associated with synthetic chemical. Neem products are said to have a destructive effect on a wide range of insects and pests. Aqueous extracts and powders of both neem and kernel interfere with the development of pod borers and pod sucking bugs.
In recognition of the problems associated with insecticide use in the production of local food crops, many farmers use organic (manure) from plant and animal materials. Local manure provides all the nutrients namely: nitrogen, phosphorus and potassium needed for plants to grow healthy and yield highly and protects the crops. The organic fertilizers are more environmental friendly and less likely to pollute the nearby water sources. Tephrosia, a perennial leguminous shrub also has the potential of controlling pests like the maize stalk borer. Sun dried guava and eucalyptus leaves are also found to act as repellants against the rice weevil.
To ensure high agricultural production, the push today is for genetically engineered crops. At the vanguard of the revolution is a generation of robust plants more resistant than their predecessors to heat and cold, drought, a range of pest and crop disease. Tobacco for example, is modified using a technique known as chemical shielding, in which the tobacco receives a gene that makes it resistant to bromoxynil, one of the most commonly used herbicides.
Companies are studying ways to make the herbicides and pesticides safer. Britain Imperial Chemical Industries (ICI), for instance, has developed and fine-tuned an insecticide to kill destructive insects while permitting harmless and helpful critters to survive. Dubbed Poromicarb, the insecticide kills the destructive aphid but does not harm the ladybug, a predator that helps control a range of destructive pest.
Monsanto’s herbicide Roundup, blocks protein production in the encroaching weeds, effectively halting their growth. It breaks down once it has completed its job, eliminating the danger of ground and crop contamination. Sandoz has developed fungicides to protect cereals, fruit, vines and vegetables from fungal diseases. Alto, one of the company's newest products, interferes with the growth of organisms that attack small grain plants. A new irrigation technique developed by Italy's Ferruzzi Group, uses a series of underground plastic pipes, which capture water that has been mixed with fertilizers and pesticides. The water and chemicals are recycled, reducing the amount of fertilizers and pesticide required and preventing toxic liquid residues from seeping into the ground.
Its not known how long it will take for such technology to reach the African farmers, and whether it will be affordable for the small-scale majority farmers. The use of insecticide is must for most of these genetically modified crops, yet many African farmers are trying to avoid. In many farming villages in Uganda, cultural farming techniques are still very easily noticeable and highly practiced to protect crops and attain better yields.
By Judy Auma
Miss Auma is an African Executive Staff Writer based in Uganda
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