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

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

The Chittagong story: studies on the ecology of rat floods and bamboo masting

Rodent population outbreaks due to the 50-year cycle of gregarious flowering and seed masting of Melocanna baccifera were first noted in the Chittagong Hill Tracts (CHT) of Bangladesh during the crop production cycle of 2008. The wave of flowering has steadily moved southward through the region each year, with seed masting still occurring in some areas of the CHT during 2010. Because of a lack of surveillance, it is not yet known whether all Melocanna bamboo forests across the region have now initiated flowering. Ecological surveys carried out during the masting event have provided some preliminary evidence that nearly all rodent species are able to exploit Melocanna bamboo seeds as a food resource, with nearly 30% of the seed fallen in forests damaged by rodents. Breeding potential of the predominant species found, Rattus rattus, appears to confirm that aseasonal breeding occurs due to the abundant supply of bamboo seed during masting events. These preliminary results obtained from ongoing research surveys are discussed in the context of the management response to the regional famine triggered by the severe crop damage caused by rodent population outbreaks

Conducting ethanobotanical surveys: an example from Ghana on plants used for the protection of stored cereals and pulses (NRI Bulletin 77)

A survey was undertaken in the Ashanti Region of Ghana to assess the use of plant materials with insecticidal and repellent properties on local farms. Emphasis was placed on plant materials used to protect stores containing cereals and pulses. A total of 27 plant species were recorded as having protective qualities against storage pests of cereals and pulses. The species Chromolaena odorata (L.) [siam weed], Azadirachta indica A. Juss [neem] and Capsicum annuum L. [chilli pepper] were the most commonly used to protect stored food. In addition to plants used to protect stored products, bio-activity against insect pests was reported in approximately 95 plant species. The most frequently mentioned plant species were Bambusa vulgaris Schrad. [bamboo], Citrus spp. [lime, lemon and orange], Datura innoxia Mill., Manihot esculenta Crantz [cassava] and Piper umbellatum L. The survey found that 26% of the farmers interviewed used botanicals in some form for stored product protection; however, only a small percentage (7%) relied on them exclusively to protect their harvest from storage pests. Smoking of maize stores was the most common method of control in most districts (28%), with the exception of the major maize-growing districts (Ejura and Mampong), where the majority of farmers used conventional insecticides for the control of stored product pests

Responses to colour and host odour cues in three cereal pest species, in the context of ecology and control

Many insects show a greater attraction to multimodal cues, e.g. odour and colour combined, than to either cue alone. Despite the potential to apply the knowledge to improve control strategies, studies of multiple stimuli have not been undertaken for stored product pest insects. We tested orientation towards a food odour (crushed white maize) in combination with a colour cue (coloured paper with different surface spectral reflectance properties) in three storage pest beetle species, using motion tracking to monitor their behaviour. While the maize weevil, Sitophilus zeamais (Motsch.), showed attraction to both odour and colour stimuli, particularly to both cues in combination, this was not observed in the bostrichid pests Rhyzopertha dominica (F.) (lesser grain borer) or Prostephanus truncatus (Horn) (larger grain borer). The yellow stimulus was particularly attractive to S. zeamais, and control experiments showed that this was neither a result of the insects moving towards darker-coloured areas of the arena, nor their being repelled by optical brighteners in white paper. Visual stimuli may play a role in location of host material by S. zeamais, and can be used to inform trap design for the control or monitoring of maize weevils. The lack of visual responses by the two grain borers is likely to relate to their different host-seeking behaviours and ecological background, which should be taken into account when devising control methods

Survival and recruitment of the multimammate mouse, Mastomys natalensis (Smith 1834), in a rice agro-ecosystem

We investigated the recruitment and survival of the multimammate mouse, Mastomys natalensis, within irrigated rice and fallow field habitats at different time periods related to rice crop growth stages. Capture-Mark-Recapture data were collected for M. natalensis each month from June 2010 to May 2012, and both recruitment and survival were estimated in relation to land use (irrigated rice or fallow field) within the agro-ecosystem. Higher recruitment and survival were observed in rice fields than in fallow fields suggesting the relationship was compensatory when there was a higher abundance of food resources. In terms of management, farmers in the study area should implement management strategies in rice fields at both transplanting and maturity stages of crop growth in order to maintain recruitment and survival at low levels.The Zonal Agricultural Research and Development Funds (ZARDEF) through Eastern Zone.http://www.degruyter.com/view/j/mamm2017-03-30am2016Mammal Research InstituteZoology and Entomolog

The biology of the deathwatch beetle, Xastobium rufouillosum de Geer (Coleoptera: Anobiidae)

SIGLEAvailable from British Library Document Supply Centre-DSC:DXN028340 / BLDSC - British Library Document Supply CentreGBUnited Kingdo

Host selection behaviour of deathwatch beetle, Xestobium rufovillosum: Oviposition preference choice assays testing old vs new oak timber, Quercus sp.

In a choice bio-assay adult female deathwatch beetles were offered two dendrochronologically dated wood blocks from oak timber to study oviposition preference behaviour. There was a clear preference for ovipositing on old wood dating from the 13th to 19th centuries rather than new wood from the 20th century. Control, same-century choice, experiments showed that beetles will oviposit on young wood and that the age of the wood does not alter the overall oviposition potential. Oviposition frequency varied with insect age. Fecundity of insects collected from an infested building was similar to that of insects maintained in culture

Predation by small mammalian carnivores in rural agro-ecosystems: An undervalued ecosystem service?

Africa is endowed with a diverse guild of small carnivores, which could benefit stakeholders by providing ecosystem services while fostering conservation tolerance for carnivores. To investigate the potential of small carnivores for the biological control of rodents within agro-ecosystems, we assessed both the ecological and social landscapes within two rural villages in the Vhembe Biosphere Reserve, South Africa. We employed a camera trapping survey underpinned by an occupancy modelling framework to distinguish between ecological and observation processes affecting small carnivore occupancy. We also used questionnaires to investigate perceptions of small carnivores and their role in pest control. We found the greatest diversity of small carnivores in land used for cropping in comparison to grazing or settlements. Probability of use by small carnivores was influenced negatively by the relative abundance of domestic dogs and positively by the relative abundance of livestock. Greater carnivore diversity and probability of use could be mediated through habitat heterogeneity, food abundance, or reduced competition from domestic carnivores. Village residents failed to appreciate the role of small carnivores in rodent control. Our results suggest that there is significant, although undervalued, potential for small carnivores to provide ecosystem services in agro-ecosystems