The hurdle of adoption has been tackled using participatory methods of extension; one such project was highly successful in allowing farmers to reduce inputs costs, mostly due to reductions in insecticide use, while maintaining and often increasing vegetable yields and incomes. This requirement for farmer training in IPM is reflected in initiatives around the continent for key crops, many based on participatory methods and the farmer field schools.

Biological control has a long history in Africa. Since the early 20th century, South Africa has been a leading world player, particularly in the biological control of weeds, e.g., Opuntia and Harrisia cacti, Acacia spp., Hypericum perforatum, Sesbania puniceae, Hakea sericea, Solanum spp., Lantana camara and many water weeds (Pistia stratiotes, Salvinia molesta, Azolla filiculoides, Myriophyllum aquaticum, Eichhornia crassipes) (Neuenschwander et al., 2003). An early example of biological control is the control of coffee mealybug (Phenacoccus kenyae) following its emergence on Kenyan coffee estates in the 1920s. Correct identification facilitated classical biological control introductions in the late 1930s which, in conjunction with banding, quickly achieved local success. Good country-wide control was achieved by the end of the 1940s. Although use of persistent (chlorinated hydrocarbon) insecticides led to resurgences in the 1950s on estates, smallholder coffee was not affected. While the economic returns to smallholders have never been quantified, estimates in 1959 indicated a £10 million saving for the coffee industry for an expenditure of no more than £30,000 (Greathead, 1967). Cost is often cited as a barrier to biopesticide adoption, particularly in Africa where farm incomes are low and biopesticides have to be imported. A factory for Bacillus thuringensis (Bt) in Nairobi, Kenya began production in 2004 and Green Muscle®, a mycopesticide, is being manufactured in Africa. Capacity for biopesticide development and manufacturing is currently limited.

Biological control in IPM involves augmentation or conservation/manipulation of often local—sometimes introduced where they are naturalized—natural enemy populations to make them more effective in suppressing pest populations. An innovative method developed in Africa exploits natural enemies in the IPM context in what has become known as the “push-pull” (www.push-pull.net/) habitat management strategy. Developed for stemborer pests in maize in East Africa, the approach involved using intercrops to modify the behavior of the pest—and its natural enemies. At its simplest, chemicals produced by specific plants planted adjacent to the crop (e.g., molasses grass) attract pest out of the crop; while chemicals produced by specific crops (e.g., the legume Desmodium) interplanted with the crop repel pests. The net result is less pest attack on the crop and more parasitism. Following this breakthrough, observations that the parasitic weed Striga was suppressed in the presence of Desmodium led to the development of a management system for two of the major constraints to maize production in East Africa: cereal stemborers and Striga.

The success of AKST in recent decades has often masked significant externalities affecting both natural capital and human health. Reports of environmental and health problems associated with chemicals have increased, though statistical analyses of such problems are lacking. Legislation can

either encourage or discourage the use of natural biological control products, which offer more benign inputs for crop production. Farmers often lack the necessary information to develop better pest management through experimentation. Formal research may be instrumental in providing the input necessary to facilitate participatory technology development such as that done by farmer field schools.

2.1.6 Processing and value addition
Conventional processing is used mainly to reduce postharvest losses and create more convenient products. In processing, a material is transformed from one state to another and its value increases. Value addition is a deliberate operation to produce a totally new and different product. Both conventional processing and value addition approaches make use of science and technology developments.

There are two types of processing: traditional and improved/ industrial methods. Traditional processing may be as old as humans. People who lived a life of hunting and gathering smoked and dried meat to preserve it. Fermenting of food staples is a widely used traditional method in West Africa and is still disseminated to communities in other countries. Using biochemistry, physiology, physics and engineering knowledge, traditional methods of processing have been gradually improved upon and have contributed to the development of industrial methods (Asiedu, 1989).

Food security, nutrition improvement and urbanization are among key drivers of food crop processing. Income generation has driven nonfood crop processing and the production of nonfood products from food crops. Food staple crop processing plays a role in reducing post-harvest losses. For example, cassava processed into Gari, flour and chips can be stored or preserved for a longer time than fresh tubers and can be kept during bumper periods to be used for food during lean seasons. About 25% of food grown in the tropics is lost before utilization (Asiedu, 1989). The processing of human food staples and animal feed can lead to value-added wholesome and nutritious foods that can be safely packaged for convenience. Several crops (direct produce or residues) are processed into different types of animal feed with greater nutritional value than individual fodder crops.

Urbanization continues to call for increased and improved processing and value addition in order to obtain food stuff in forms that are convenient to prepare into meals. Foods with shorter cooking/preparation times are less laborintensive and have extended shelf life. This was exemplified in a shift from local food staples to introduced wheat and rice in West Africa in the late 1970s.

While traditional methods have been used to transform foodstuffs from one state to another, the products are usually not of optimum quality and standards. Inconsistency is common in products from the same or various processors, a problem being addressed gradually with continuous innovation and improved technologies. For example, cassava is processed into different food products in West Africa and into industrial (nonfood) products such as starch and alcohol and flour used in adhesives in many other countries. Traditionally produced flour may vary in color, level of fermentation and be contaminated with dirt. Traditional processing methods have been improved through centrifugation, hot air driers and sieving, thus improving the qual-