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Managing legume pests in sub-Saharan Africa: Challenges and prospects for improving food security and nutrition through agro-ecological intensification

Managing legume pests in sub-Saharan Africa: Challenges and prospects for improving food security and nutrition through agro-ecological intensification

Belmain, S.R. ORCID: 0000-0002-5590-7545, Haggar, J. ORCID: 0000-0002-4682-4879, Holt, J. and Stevenson, P.C. ORCID: 0000-0002-0736-3619 (2013) Managing legume pests in sub-Saharan Africa: Challenges and prospects for improving food security and nutrition through agro-ecological intensification. [Working Paper]

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Pest management technology has been through a number of advances that have, perhaps, moved away from the mass extermination of pests achieved through the advent of synthetic chemicals in the latter half of the 20th century to more agro-ecologically sensitive innovations that attempt to regulate pest populations by interfering with their breeding, attracting predators or repelling the pests from crops whilst attracting them to other plants. However, pest management is more than technology innovations and must enable integration of technologies in a practical and cost-beneficial manner. This paper summarises existing and cutting edge technologies for pest management in the context of legume production in Africa highlighting where advances can be made to improve pest management at the smallholder level. Challenges and opportunities are highlighted, and priorities for research are recommended that complement agro-ecological intensification (AEI). AEI describes the sustainable increase in agricultural production from the same amount of available land area while reducing the negative environmental impacts of agricultural technology (‘Reaping the Benefits’ – The Royal Society, 2009; Green Food Report - Defra, 2011; ‘Sustainable Intensification‘ - Montpellier Report, 2013). AEI aims to harness knowledge of ecological processes to increase food production and improve livelihoods and challenges global agriculture to achieve a doubling in world food production while sustaining the environment in which we live.

Synthetics are relatively cheap and provide proven pest control. They are substantially underutilised in Africa and could lead to significant productivity increases if their usage could be increased to levels found in other regions of the world. Challenges and opportunities to increased uptake are
• Monetary cost to small holder farmers – cost-benefit not clear when produce is typically not sold or when market values are marginal
• Limited end user knowledge on how to use synthetics leads to excessive use, reduced cost-benefit and subsequent environmental and safety hazards, under-dosing and resistance development, use of wrong pesticide for crop and pest, high poisoning rates to users and consumers
• Poor regulation leads to adulteration, dumping, limited availability, repackaging without labelling

Pesticidal plants are cheap, generally only requiring labour to collect and process, and fit well within IPM and AEI strategies. Most African farmers are familiar with botanicals, but usage is constrained by a number of factors related to gaps in research and development and how they are regulated. Challenges and opportunities to uptake are
• Although generally low-risk, safety data are lacking.
• Hundreds of plant species have been evaluated for efficacy, factors influencing reliability of efficacy are unknown, e.g. that influence the production of bioactive constituents (altitude, season, soil type), that effect the amount of bioactive compounds extracted (solubility, volatility) or the duration/level of control to be expected for different pest species.
• A high level of knowledge is required to use pesticidal plants (when/where to harvest, how to prepare/extract) although much of this may already be known
• Availability of sufficient plants can be limited and/or unreliable due to over-collection, unsustainable collection or competing uses (medicine, fodder, food, fibre) as well as poor propagation properties or habitat conservation
• Regulatory frameworks treat pesticidal plants in the same way as synthetics, and high registration costs of existing systems prevent developing products which cannot be protected by patent making it difficult to invest in registration costs
• Complex chemistry makes registration of products difficult
• Variability in efficacy is a limiting factor but can be managed by selection of effective provenances for propagation

Biopesticides are highly appropriate for IPM and AEI of legume crop production. Several products exist that could contribute to improved legume production in Africa. Challenges and opportunities to uptake are
• The cost of products generally puts them out of reach of small holder farmers
• Shelf life of products is often limited, requiring relatively sophisticated marketing chains to improve delivery of high quality products
• Cost-benefits not clear due to input price vs. potential income or gain in food security/nutrition
• Research and development is focussed on servicing developed country needs, often advanced technology/knowledge is required to mass produce biopesticides.
• Effects often not immediately evident and pest takes days to control leaving farmers uncertain of their benefits

Biocontrol organisms are highly appropriate for IPM and AEI of legume crop production. Artificial augmentation of predators and parasitoids can work well, but is generally expensive to produce and works best with high value crops in enclosed environments, such as glasshouses, where it is relatively easier to maintain investment and prevent escape of organisms. Augmentation in small holder legume farming systems is probably not cost-beneficial in the short to medium term in Africa. However improving farming practice to improve ecosystem services of natural biocontrol is feasible. Challenges and opportunities to uptake of natural biocontrol are
• More research is required on the alternative crop requirements and optimal environments for predators and parasitoids as it is still not clear how best to optimise predator numbers for key pests or what level of pest control can be achieved
• Increasing end user knowledge on how to improve (engineer) environments that increase predation combined and enhance pollinators
• Understanding costs and benefits of improved biocontrol, particularly when physical inputs are required (e.g. planting/maintaining trap crops or overwintering crops)
• Increasing farmer knowledge on the impact of general farm practices on biocontrol (frequent use of generic synthetic pesticides, field clearing with fire)

Semiochemicals are highly appropriate for IPM and AEI of legume crop production. Pheromone traps can be cost-effective for monitoring important pests like army worm or pod borer, particularly if implemented at the community level. The cost-benefits of pheromones to manage pest populations (through mating disruption or removal trapping) is less clear and currently only works for some key pests of high value crops. The use of naturally released semiochemicals through push-pull cropping strategies has been shown to be highly beneficial for reducing key maize pests in smallholder farming. Despite this, evidence of uptake by African farmers has been limited even when heavily promoted through intensive knowledge training programmes. Challenges and opportunities to uptake are
• The cost of products generally puts them out of reach of smallholder farmers
• Efficacy may be limited
• Knowledge to use effectively is high

Resistance mechanisms are arguably the most effective method for delivering improved pest management to small holder farmers. Farmers may have to buy seed, but then often don’t need to make any further inputs to receive benefits of lower pest problems. If non-hybrid resistant varieties are developed, farmers can self-propagate the crop for many years. Challenges and opportunities to uptake are
• The costs of developing new varieties is coming down through the use of gene marker technologies; however, developing resistant varieties still requires a significant research investment, often supported by the public sector.
• Adding resistance often means enhancing the natural production of detrimental compounds with in the plant, which may have effects on consumer health and safety and/or pollinators/ecosystem services.
• The cost-benefits may be high for farmers, but if adding in the R&D investment, it is not clear whether overall cost-benefits to society are positive, particularly if insects rapidly adapt to resistance mechanisms requiring further investment in varietal development.
• Some of the more rapid methods of resistance breeding, e.g. genetic modification, remain controversial

The development of strategies to enhance agro-ecosystem resilience is by definition an integral part of IPM and AEI in legume production. In many cases farmers already employ traditional practices which improve agroecosystem resilience. Frequently, the practices do not require expensive inputs or elaborate technology. Challenges and opportunities to uptake are
• The strategies may be multi-facetted and complex with diverse objectives rather than being a more tangible single technology directed at a specific problem. This impinges on issues of training and clarity in what is being offered
• Strategies tend to be beneficial to the health of the agro-ecosystem in general (soils, nutrition, water, pollination) but often have limited direct effect on pests
• Conflicts may exist between objectives so, for example, use of green manure while having advantages for soil, nutrition and water, can also increase soil pest problems
• Perhaps more than other approaches, agro-ecosystem resilience strategies are not ‘one size fits all’, and must be tailored to local conditions, e.g. appropriate intercropping strategies are dependent on the cropping system and culinary context
• Some strategies, e.g. incorporation of areas of natural vegetation in the agro-ecosystem landscape, require implementation of wide geographical scales in order to achieve most benefit

Agroecological pest management by small holder farmers in Africa requires building substantial understanding of crop-pest-environmental interactions, which requires investment in training by institutions and farmers. This presents certain challenges and opportunities:
• Farmer field school approaches are well developed in many parts of Africa and have been successfully used in Asia to develop capacity for agroecological pest management. The experience in Africa has been that only a limited number of farmers invest in building agroecological reasoning into their management, but FFS have been effective in promoting farmer to farmer technology transfer.
• Agroecological knowledge based pest management has been more successful in higher value crops, with complex pest problems, and where use of pesticides may be limited by regulation or have limited effectiveness.
• Research and validation is required is develop discovery-based learning approaches that will enable farmers to take informed decisions needed for agroecological pest management.

Item Type: Working Paper
Additional Information: [1] Suggested citation: Belmain, S.R., Haggar, J., Holt, J. and Stevenson, P.C. (2013). Managing legume pests in sub-Saharan Africa: Challenges and prospects for improving food security and nutrition through agro-ecological intensification. Chatham Maritime (United Kingdom): Natural Resources Institute, University of Greenwich. 34p. [2] Acknowledgement (funding): the McKnight Foundation for partially funding the preparation of the manuscript. [3] Copyright © University of Greenwich 2013. This publication is copyrighted by the University of Greenwich (UoG) and is licensed for use under a Creative Commons Attribution – NonCommercial – ShareAlike 3.0 License.
Uncontrolled Keywords: legume, Africa, pest management
Subjects: S Agriculture > S Agriculture (General)
Faculty / School / Research Centre / Research Group: Faculty of Engineering & Science > Natural Resources Institute
Faculty of Engineering & Science > Natural Resources Institute > Agriculture, Health & Environment Department
Related URLs:
Last Modified: 23 Apr 2019 10:41

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