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

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

Sweetpotato weevil resistance in sub-saharan Africa: A viable mechanism for reducing Cylas damage.

Sweetpotato (Ipomoea batatas, L) is the third most important crop in Sub-Saharan Africa contributing significantly to food security, nutrition and income. Weevils, Cylas spp., are the most important insect pest of the crop. The weevils damage both vines and roots, causing unacceptable odour, discoloration, and bitter taste making them unfit for consumption. Depending on conditions, weevils can cause complete losses of the harvestable crop. Host plant resistance seems to be the only viable option for management of the pest. Studies in Uganda reveal existence of active resistance in some sweetpotato genotypes. Field and laboratory experiments show that clones HMA 519, ARA 230, LIR 302, APA 356, ARA 228, RAK 865 (local), and New Kawogo (improved), have varying levels of resistance compared to the susceptible varieties NASPOT1, Kakamega, and Tanzania. The resistant clones were evaluated for field resistance against the susceptible checks; root and vine damage was less in the resistant clones. No-choice bioassays using roots conducted in the laboratory to show that feeding and oviposition was less on the resistant clones indicating that the observed field resistance was not simply escape. The resistance has been linked to some hydroxycinnamic acid esters which occur in higher concentrations in the roots of resistant compared to the susceptible clones. The compounds were extracted from the roots, analysed and synthetic derivatives used to conduct toxicity & deterrence tests. Different concentrations (0.001, 0.01, 0.1mg/ml) of synthetic derivatives of the compounds were applied to the root surfaces of the susceptible variety (NASPOT 1) and showed that weevil species from both Uganda and Malawi fed less and laid fewer eggs on the treated roots compared to the untreated ones confirming the activity of the compounds against weevils. Preliminary studies indicate that the compounds have an additive effect with Cry7a proteins which are the target for the development of clones transformed with the Bt toxin. The findings have important implications for the breeding program in Uganda and will be used to map QTLs in segregating populations from a cross between the US variety Beauregard and the Ugandan variety New Kawogo

Outstanding Questions in Flower Metabolism

The great diversity of flowers, their color, odor, taste, and shape, is mostly a result of the metabolic processes that occur in this reproductive organ when the flower and its tissues develop, grow, and finally die. Some of these metabolites serve to advertise flowers to animal pollinators, other confer protection towards abiotic stresses, and a large proportion of the molecules of the central metabolic pathways have bioenergetic and signaling functions that support growth and the transition to fruits and seeds. Although recent studies have advanced our general understanding of flower metabolism, several questions still await an answer. Here, we have compiled a list of open questions on flower metabolism encompassing molecular aspects, as well as topics of relevance for agriculture and the ecosystem. These questions include the study of flower metabolism through development, the biochemistry of nectar and its relevance to promoting plant‐pollinator interaction, recycling of metabolic resources after flowers whiter and die, as well as the manipulation of flower metabolism by pathogens. We hope with this review to stimulate discussion on the topic of flower metabolism and set a reference point to return to in the future when assessing progress in the field

Connected Green function approach to ground state symmetry breaking in Φ1+14\Phi^4_{1+1}-theory

Using the cluster expansions for n-point Green functions we derive a closed set of dynamical equations of motion for connected equal-time Green functions by neglecting all connected functions higher than $4^{th}$ order for the $\lambda \Phi^4$-theory in $1+1$ dimensions. We apply the equations to the investigation of spontaneous ground state symmetry breaking, i.e. to the evaluation of the effective potential at temperature $T=0$. Within our momentum space discretization we obtain a second order phase transition (in agreement with the Simon-Griffith theorem) and a critical coupling of $\lambda_{crit}/4m^2=2.446$ as compared to a first order phase transition and $\lambda_{crit}/4m^2=2.568$ from the Gaussian effective potential approach.Comment: 25 Revtex pages, 5 figures available via fpt from the directory ugi-94-11 of [email protected] as one postscript file (there was a bug in our calculations, all numerical results and figures have changed significantly), ugi-94-1

The climatic challenge: which plants will people use in the next century?

More than 31,000 useful plant species have been documented to fulfil needs and services for humans or the animals and environment we depend on. Despite this diversity, humans currently satisfy most requirements with surprisingly few plant species; for example, just three crops – rice, wheat and maize – comprise more than 50% of plant derived calories. Here, we synthesize the projected impact of global climatic change on useful plants across the spectrum of plant domestication. We illustrate the demographic, spatial, ecophysiological, chemical, functional, evolutionary and cultural traits that are likely to characterise useful plants and their resilience in the next century. Using this framework, we consider a range of possible pathways for future human use of plants. These are centred on two trade-offs: i) diversification versus specialization in the range of species we utilize, and ii) substitutionof the species towards those better suited to future climate versus facilitating adaptation in our existing suite of dominant useful plants. In the coming century, major challenges to agriculture and biodiversity will be dominated by increased climatic variation, shifting species ranges, disruption to biotic interactions, nutrient limitation and emerging pests and pathogens. These challenges must be mitigated, whilst enhancing sustainable production to meet the needs of a growing population and a more resource intensive standard of living. With the continued erosion of biodiversity, our future ability to choose among these pathways and trade-offs is likely to be diminished

Towards an understanding of unique and shared pathways in the psychopathophysiology of AD/HD

Most attention deficit hyperactivity disorder (ADHD) research has compared cases with unaffected controls. This has led to many associations, but uncertainties about their specificity to ADHD in contrast with other disorders. We present a selective review of research, comparing ADHD with other disorders in neuropsychological, neurobiological and genetic correlates. So far, a specific pathophysiologicalpathway has not been identified. ADHD is probably not specifically associated with executive function deficits. It is possible, but not yet established, that ADHD symptoms may be more specifically associated with motivational abnormalities, motor organization and time perception. Recent findings indicating common genetic liabilities of ADHD and other conditions raise questions about diagnostic boundaries. In future research, the delineation of the pathophysiological mechanisms of ADHD needs to match cognitive, imaging and genetic techniques to the challenge of defining more homogenous clinical groups; multi-site collaborative projects are needed. © Blackwell Publishing Ltd

Quantitative analysis of ruminal bacterial populations involved in lipid metabolism in dairy cows fed different vegetable oils

Vegetable oils are used to increase energy density of dairy cow diets, although they can provoke changes in rumen bacteria populations and have repercussions on the biohydrogenation process. The aim of this study was to evaluate the effect of two sources of dietary lipids: soybean oil (SO, an unsaturated source) and hydrogenated palm oil (HPO, a saturated source) on bacterial populations and the fatty acid profile of ruminal digesta. Three non-lactating Holstein cows fitted with ruminal cannulae were used in a 3x3 Latin square design with three periods consisting of 21 days. Dietary treatments consisted of a basal diet (Control, no fat supplement) and the basal diet supplemented with SO (2.7% of dry matter (DM)) or HPO (2.7% of DM). Ruminal digesta pH, NH3-N and volatile fatty acids were not affected by dietary treatments. Compared with control and HPO, total bacteria measured as copies of 16S ribosomal DNA/ml by quantitative PCR was decreased (P < 0.05) by SO. Fibrobacter succinogenes, Butyrivibrio proteoclasticus and Anaerovibrio lipolytica loads were not affected by dietary treatments. In contrast, compared with control, load of Prevotella bryantii was increased (P < 0.05) with HPO diet. Compared with control and SO, HPO decreased (P < 0.05) C18:2 cis n-6 in ruminal digesta. Contents of C15:0 iso, C18:11 trans-11 and C18:2 cis-9, trans-11 were increased (P < 0.05) in ruminal digesta by SO compared with control and HPO. In conclusion, supplementation of SO or HPO do not affect ruminal fermentation parameters, whereas HPO can increase load of ruminal P. bryantii. Also, results observed in our targeted bacteria may have depended on the saturation degree of dietary oils