The objective of this research is to assess the effects of the use of insect nets in vegetable production. To achieve this goal, data were collected in four departments of southern Benin (Mono, Couffo, Ouémé and Plateau) using an interview guide and a structured questionnaire. A total of 223 producers chosen at random from these areas where the CRSP Horticulture Project is located were surveyed. The results of the study show that growers using insect nets have not given up using chemical pesticides. However, a significant reduction in treatment frequencies was recorded in the nursery and after transplanting for most of the pesticides identified. Similarly, a significant reduction (more than 60.0%) in pest attacks (Helicoverpa armigera, Hellula undalis, Plutella xylostella, Bemisia tabaci and cochineals) was recorded among producers using anti-insect nets at 5%. These results involve that it is necessary to sensitize farmers to the use of nets to protect plants. This will significantly reduce pest attacks and reduce the use of pesticides in production. Key words: Anti-insect nets, effects, pests, market gardening, Benin.

Summary Although several studies have underlined the advantages of using insect-proof nets to improve yields while reducing the use of pesticides, one obstacle to the diffusion of this technique in tropical conditions is the associated increase in temperature in the tunnel. The aim of this work was to assess the interest of combining the physical protection provided by nets against insect pests with the beneficial impacts of using shade nets to grow cabbages. A two-season experiment was set up to compare temperature conditions, insect pest populations, yields, and the quality of cabbage crops grown in the open field and in low tunnels covered with nets providing different degrees of shading, 17.2% by white and 50.1% by silver nets. During the day, the temperature under the white and silver nets was 10.4 °C and 6.3 °C higher, respectively, than in the open field in the first season, and 6.5 °C and 5.9 °C higher in the second season. Both insect-proof nets significantly reduced insect pest populations and hence the need for insecticide treatments. The white nets increased marketable yield by 45.4% in the first season and by 16.4% in the second compared to yields in the open field, whereas silver nets reduced yield by 18.6% and 15.0%, respectively. The reduction in yield under silver nets was attributed to excessive shading that prevented the light requirements of cabbage crops from being fulfilled. Economic analysis raised some concerns about the profitability of the use of netting to grow cabbage due to investment costs and the lack of premium prices for vegetables produced with fewer pesticides in local markets.

L'accroissement en quantite et en frequence des apports de produits residuaires organiques (PRO), en contexte periurbain tropical modifient les conditions physico-chimiques du milieu, la dynamique des elements traces (ET) ainsi que les activites biologiques du sol. Sur la station de l'Isra a Sangalkam, trois cultures en rotation (laitues, carottes et tomates) ont fait l'objet de suivis sur le rendement, la qualite des recoltes (matiere seche, forme et calibre) et les teneurs en ET. Les quantites de N, P et K pour les cultures ont ete determinees et apportees par une fertilisation minerale (T0) et/ou par differents PRO (boue de station/B1, digestat/DM1 et litiere de volaille/LV1) afin de pouvoir (i) comparer au cours de trois annees de cultures les types d'apports, (ii) de tester un recyclage optimal des PRO et (iii) une augmentation des rendements des cultures avec les doses doubles (B2, DM2 et LV2). LV2 a donne les meilleurs rendements pour les cultures de laitue et tomate (30,78±14,66 t/ha et 43,82±19,36 t/ha) avec des differences significatives entre T0 et LV2 au cours des cycles pour les cultures de laitue. Les carottes a forme normale avec un volume important ont ete plus eleve avec les fortes doses (LV2 = 41,36 % et DM2 = 32,52 % vs T0 = 32,52 %), contrairement pour B2 = 23,92 %. Les biomasses seches de laitue ont ete significativement plus eleve avec LV2 (20, 23 ± 8, 23 g). B2 a produit significativement plus de tomates a diametre 30–47 mm que de tomate a diametre >47 mm (73,96 % vs 26,04 %). Les teneurs en ET des laitues ont diminue significativement au cours des cycles, contrairement a celle des tomates (P< 0,0001). La valorisation agronomique de la litiere de volaille a montre les meilleurs resultats pour la production de legume de qualite avec des rendements eleves. Cependant, la physiologie des cultures est un facteur determinant pour expliquer la trajectoire d'evolution des ET.

Les rendements en agriculture biologique font l’objet de controverses et sont considérés comme plus faibles qu’en agriculture conventionnelle. En Afrique, l’agriculture biologique recouvre une grande diversité de pratiques et les rendements présentent de fortes incertitudes. Les analyses des rendements et des itinéraires techniques en agriculture biologique sont présentées pour trois cultures maraîchères au Sénégal. Les résultats sont ensuite comparés aux rendements usuels de l’agriculture conventionnelle. Deux types de données sont utilisés, provenant de parcelles d’agriculteurs : i) suivi de champs conduits selon des itinéraires techniques d’agriculture biologique vs. itinéraires techniques conventionnels ; ii) résultats issus des actions de l’organisation non gouvernementale ENDA-PRONAT, suivant un cahier des charges copié sur celui de l’agriculture biologique. Les suivis comparatifs de parcelles de chou pommé et de tomate en saison des pluies mettent en évidence des ratios de rendement agriculture biologique/conventionnelle de 74 et 40 % respectivement. Ces valeurs confirment la tendance générale des résultats de la littérature. Elles sont expliquées par une fertilisation azotée plus faible et l’absence de mesures de protection efficace contre les maladies et ravageurs des cultures. Les rendements en oignon des parcelles d’agriculture biologique chez les producteurs sont très variables : en moyenne de 19,4 t/ha à 11,0 t/ha suivant les années dans la zone des Niayes, 21,0 t/ha dans le Bassin arachidier et seulement 8,6 t/ha dans la vallée du fleuve Sénégal. Les rendements de la culture d’oignon au Sénégal observés dans la littérature varient aussi dans de grandes proportions, de 10,7 à 32 t/ha. Dans certains cas, les rendements en agriculture biologique sont supérieurs à ceux des itinéraires techniques de l’agriculture conventionnelle. Ce constat, déjà observé dans la littérature scientifique, montre que l’agriculture biologique est une voie de développement de l’agriculture à ne pas écarter en Afrique.

The rapid expansion of cities in sub-Saharan Africa generates increasing volumes of diversified organic wastes that require management and a high population need for local and fresh vegetables. Linking the different sources of organic materials generated in these cities with the needs of local food producers for fertilizers prepared from recycled organic materials is challenging. This requires that producers obtain the results they expect from the organic materials they recycle. Thus, recycling these organic materials in their raw form or after composting presents an opportunity for periurban agriculture, although the great variability in the quantity and quality of these materials raises questions about the consistency between their agronomic value and their economic value. In two large cities of Cameroon (Yaoundé and Bafoussam), different types of organic materials were sampled: unprocessed livestock waste and composts from manure or municipal solid waste. From an agronomic perspective, we calculated the fertilization value based on the nutrient (nitrogen, phosphorus, and potassium) content of the organic materials. From an economic perspective, we calculated the value based on the nutrient content of the organic materials and their substitution unit prices and recorded the current market price. This is the first time that this combined approach has been used in sub-Saharan Africa. Our results showed considerable variability and discrepancy in both the agronomic and the economic values. The market prices overvalued the urban composts by a factor of 6, while chicken feces were undervalued by a factor of 3. The unprocessed organic materials were the most interesting from an economic and agronomic perspective. Our findings suggest that (i) the composting process needs to be improved and (ii) the humus potential should be calculated to better assess the amendment value of organic materials and as a basis for adjusting their market price.

Fruits and vegetables are important commodities in global agriculture. However, in sub-Saharan Africa, production is sub-optimal in terms of yield, quality and environmental health practices due to several constraints such as insect pests which reduce yields through direct damage, or indirectly as disease vectors often promoting microbial diseases. Pest control still relies mainly on chemicals with their associated risks of resistance selection and toxicity to humans and environment. Several alternatives including biopesticides, semiochemical and nets are being explored in pest management. Insect nets applied on tomatoes, cabbages, beans and leafy vegetables protect them from flies, butterflies, moths, albeit to a lesser extent, whiteflies, aphids and thrips reducing their outbreaks as compared to open cultivation. As a result, pest control is limited and yield quantity and quality are improved. Insect nets are safe and cost effective for a period of 3-5 years if well maintained, and they may be re-used and recycled. Insect nets applied on cabbages in Benin yielded 3-fold more profit than current practice. However, insect nets are not effective against all pests inclusion of insect attractants or repellents may enhance efficacy of netting technology. The use of insect nets offers a cost-effective insect pest management option to among smallholder vegetable growers. The full benefit will be achieved with intensified extension efforts to make this technology better known.

Le developpement de la filiere maraichere au Senegal s'est appuye sur des innovations techniques comme le motopompage, l'usage d'intrants, l'ombriere-filet, … Une enquete aupres de 22 maraichers de l'agriculture familiale au sud des Niayes a montre la diversite des processus d'innovation et leurs determinants. L'adoption de l'irrigation localisee (goutte a goutte) a ete permise par les echanges entre des ouvriers des entreprises exportatrices de legumes et des maraichers de la meme region. La promotion de l'usage d'intrants naturels (biopesticide, repulsif, fumure organique) repondant a un cahier des charges « agro-ecologie » est assuree par une ONG. Enfin, differentes associations de cultures legumieres ont ete concues et adoptees par des maraichers innovateurs isoles pour repondre a la reduction de surface mais n'ont pas encore « diffusees ». Ces exemples mettent en evidence les capacites d'innovation et d'adaptation des producteurs ouest-africains. Ils nous interrogent sur le type de methodes et d'outils a mettre au point pour accompagner ces processus sans limiter la creativite des agriculteurs ni la flexibilite et les performances des systemes d'innovation locaux qu'ils ont pu creer.

Cabbage (Brassica oleracea L.) is a common vegetable whose production is severely limited by insect pest pressure in Western Africa. This study was conducted during the dry and rainy season in south Benin to evaluate the potential of tropical basil (Ocimum gratissimum L.) for repelling cabbage pests (Hellula undalis Fabricius, Plutella xylostella L. and Spodoptera littoralis Boisduval). In a complete randomized block design with four replicates, the insect infestation was compared between three association modalities: (i) cabbage intercropped with tropical basil, (ii) cabbage plots surrounded by tropical basil and (iii) control (no basil in the cabbage area). The presence of tropical basil near cabbage plots significantly reduced insect pest abundance on cabbage. Damages were also less important on cabbage intercropped with tropical basil. Among both intercropping modalities, alternate rows showed the best results in terms of reducing pest populations and damages than compared to cabbage plots surrounded by tropical basil. (Resume d'auteur)

En Afrique, la sécurité alimentaire a longtemps été considérée à l’aune des quantités d’aliments disponibles pour les différentes couches de la population. L’atteinte de cet objectif se raisonne en fonction des quantités produites et mises en marché, des capacités des marchés à importer et de la constitution par les Etats de stocks de sécurité. Plus récemment divers travaux ont montré l’importance de l’accessibilité des consommateurs à une alimentation saine et diversifiée pour atteindre la sécurité alimentaire pour tous. De même la qualité sanitaire et nutritionnelle des aliments apparait de plus en plus comme une condition de la sécurité alimentaire et plus globalement de l’atteinte de l’objectif de développement durable. Pour la première fois l’ONU et plus précisément son conseil des droits de l’Homme (2017) a soulevé la question des effets des pesticides sur la qualité des aliments et du droit à une alimentation saine pour tous les citoyens.

Vegetable production in sub-Saharan Africa faces numerous agronomic constraints that will have to be overcome to feed the increasing population and to fight malnutrition. Technology transfer and the adoption of low-tech protected cultivation techniques affordable for smallholders are believed to be able to meet this challenge. Protected cultivation techniques are a set of agricultural practices aimed at artificializing the crop environment through the use of soil covers and/or plant covers to control pests and climatic conditions. Although protected cultivation techniques may increase the yield and quality of vegetable crops and extend their production periods worldwide, the transfer of these techniques in sub-Saharan Africa raises questions about their agronomical performances, their profitability but also their environmental impacts. Are low-tech protected cultivation techniques adapted to the sustainable production of vegetables by smallholders in sub-Saharan Africa? To answer this question, we present an overview of the agronomic, economic, and environmental performances of low-tech protected cultivation techniques in sub-Saharan Africa as reported in the literature. The major conclusions that can be drawn from the review are (1) low-tech protected cultivation techniques are not suitable in all climatic conditions in sub-Saharan Africa and need to be combined with other methods to ensure adequate pest control, (2) the profitability of protected cultivation techniques relies on the capacity to offset increased production costs by higher yields and higher selling prices to be obtained with off-season and/or higher quality products, (3) breaking with existing cropping systems, the lack of technical support and skills, and the limited access to investment funding are major obstacles to the adoption of protected cultivation techniques by smallholders (4) life cycle assessments conducted in northern countries suggested that more efficient use of agricultural inputs would offset the negative impacts of protected cultivation techniques if they are properly managed, but further studies are required to be sure these results can be extrapolated to sub-Saharan Africa context.

The progression towards sustainable horticulture is usually associated with scientific and methodological breakthroughs. As a consequence, the innovation processes in the fields of biology and ecology and their agronomic implementation are increasingly recognized as main drivers to improve horticultural systems. At the same time, a horticultural system cannot be designed without good knowledge of the social and economic contexts in which it is embedded; it has to be considered as an integrated social-ecological-agrosystem. For example, the cross-knowledge derived from interdisciplinary research constitutes the backbone for building ecologically based crop ideotypes and cropping systems, including genetics, agronomy and social environmental levers and constraints. Designing new horticultural systems in such a systemic framework is also relevant to develop and better implement knowledge exchange among agents. This strong intertwining of the different research fields poses new challenges. There is a need for more participatory research and scaling-up to achieve adoption of innovations along the horticultural chain. Thus, the former linear and top-down scheme, i.e., from basic science to applied science and fieldwork, is now reconsidered and the design of innovative agricultural production systems is viewed as an integrated, interactive and participatory process where agents are dynamically interacting. The new challenge is to better combine the detailed knowledge typical of the dominant reductionist paradigm generally oriented towards the "one-size-fits-all" objective and the paradigm of complexity where the "custom-fit" approach predominates. Progressing towards these frameworks of knowledge and relationships among agents poses epistemological questions about interdisciplinarity and hybridization between scientific and non-scientific (advisor, grower) knowledge.

Dans le but de diversifier le systeme de production de la tomate et reduire l'utilisation des pesticides au Sud Benin, trois modalites d'intensification a savoir : Avec taille en plein champ , Sans taille sous AgroNet et Avec taille sous AgroNet ont ete comparees a un temoin Sans Taille en plein champ . L'effet du filet AgroNet et de la taille sur la croissance et le developpement des plants, l'efficacite du filet vis-a-vis des ravageurs et maladies, l'incidence des oiseaux, les niveaux de rendements, la modification du microclimat et la rentabilite financiere de ces systemes ont ete evalues. Les resultats indiquent que l'intensification de la production agricole sous abri AgroNet augmente certes la temperature (de 4 a 6°C) et l'humidite relative (entre 70 % et 80 %). mais n'impacte pas negativement la croissance et le developpement des plants de tomate. L'utilisation du filet a permis de reduire significativement l'incidence des oiseaux. Des rendements commercialisables de l'ordre de 50 a 57 t/ha ont ete obtenus sous filet. Les marges nettes degagees sous filet sont plus elevees sur un marche bio (407 F CFA / Kg) que sur un marche conventionnel (7 F CFA / Kg). L'etude a permis de produire des tomates saines, sans risque de residus de pesticide. (Resume d'auteur)

L'association IRRIGASC a initie en 2015 un nouveau domaine d'intervention : le developpement du maraichage en permaculture (ou agroecologie) en association concomitamment au developpement la culture des manguiers et autres arbres fruitiers qui constitue son coeur de metier. Ce modele d'agriculture doit repondre a deux objectifs : (i) permettre la diversification des revenus issus des terrains des vergers ecoles ainsi qu'un etalement sur l'annee des rentrees financieres (ii) produire des legumes de qualite en respectant l'environnement et la sante des humains et (iii) porter assistance aux couches sociales les plus pauvres du monde rural au Senegal, les femmes des zones a faible potentiel de production comme celle de Dioroup. Dans ce cadre l'association a fait appel au CIRAD pour l'aider a concevoir un modele de production maraichere robuste et pouvant fonctionner a court terme sans un appui financier au-dela de la phase d'investissement de depart. L'appui du CIRAD comprend d'une part un apport sur le choix des techniques, des especes et des equipements pour produire. D'autre part, une etude socioeconomique etablissant un diagnostic sur le fonctionnement de deux sites pilotes devant deboucher sur la proposition d'un modele de production maraichere durable d'un point de vue social et economique Le present rapport constitue la premiere contribution a cette etude. Il fait suite a une mission sur le terrain entre Dakar et la petite region de Dioroup/NDiongolor realise par Patrick Dugue du 4 au 9 mai 2016 et aux visites de Serge Simon dans les deux sites pilotes. Ces missions dans la region de Diouroup ainsi qu'a Dakar ont pu se derouler dans de tres bonnes conditions grâce a la mobilisation de tous les partenaires, des responsables des groupements maraichers et des Associations de parents d'eleves ainsi que les personnes ressources expertes en maraichage (Annexe 1). Nous tenons a remercier particulierement Khadi Loum, animatrice du projet maraichage permaculture et Djiby Diouf technicien ISRA a la retraite qui a assure la traduction. (Resume d'auteur)