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Mango-based orchards in Senegal: diversity of design and management patterns
- Isabelle Grechi, Cheikh Amet Bassirou Sane, Lamine Diame, Hubert De Bon, Aurore Benneveau, Thierry Michels, Virginie Huguenin, Eric Malezieux, Karamoko Diarra, Jean-Yves Rey
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Introduction. Mango-based orchards in Senegal occur in a large diversity of cropping systems, but few typologies of these systems exist and none are associated with their comprehensive and quantitative analysis. In this study we defined and characterized the typology of these systems based on a quantitative assessment of their planting design, management, vegetative state, hedgerow structure and infestation by a major pest of mango, the Bactrocera invadens fly. Materials and methods. Multivariate analysis and clustering methods were applied to data from 64 mango-based orchards and their surrounding hedgerows sampled in the Dakar and Thiès regions, in Senegal. Results and discussion. Four types of cropping systems were identified according to orchard design and management patterns: (1) ‘No-input mango diversified orchards’, (2) ‘Low-input mango orchards’, (3) ‘Medium-input citrus-predominant orchards’ and (4) ‘Medium-input large mango- or citrus-predominant orchards’. Orchard characteristics varied among these patterns. For instance, vegetation was dense and homogeneous in system 1, and the mortality rate of trees was high in system 2 but low in system 3. Orchards of systems 3 and 4 were mostly associated with hedgerows with, respectively, boundary-marking and defensive species. Lastly, the number of B. invadens flies was high in orchards of system 4, whereas it was low in those of system 2. Conclusion. The diversity of mango-based cropping systems in Senegal is now well described and quantified. This characterization is a preliminary step that is essential for further studies aiming to improve these systems.
Les volailles pour un contrôle biologique des adventices dans les vergers
- Anaïs Lavigne, Eddy Dumbardon-Martial, Christian Lavigne
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Introduction. Du fait des conditions tropicales humides, le contrôle des adventices est un poste important et permanent dans les dépenses d’un producteur de fruits aux Antilles. La pratique du désherbage chimique est à ce jour la plus économique, mais l’utilisation récurrente d’herbicides dans les vergers de la Martinique conduit à une érosion des sols et à une pollution des eaux. Pour pallier l’usage d’herbicides, nous avons testé l’association de volailles à un verger productif afin d’en contrôler l’enherbement. Matériel et méthodes. Le dispositif a été installé sur une parcelle de 700 m2 subdivisée en sept placettes de 100 m 2. Deux placettes ont constitué les traitements témoins ; elles ont été fauchées à la débroussailleuse. Chacune des cinq autres placettes a été soumise au pâturage de 5 oies pendant une semaine, puis au pâturage de 20 poulets pendant la semaine suivante, puis laissée sans volailles pendant trois autres semaines. Trois cycles de telles rotations ont été observés. La production de biomasse par groupe botanique (poacées, cypéracées et autres) dans les placettes expérimentales a été mesurée chaque semaine pendant les trois cycles (4 mois). Une fois par mois l’indice de recouvrement par groupe botanique a été relevé. Résultats. La biomasse totale de la strate herbacée a diminué sur les placettes pâturées, ce qui a permis le contrôle biologique des adventices pendant quatre mois. La diversité floristique a diminué à cause de la sélection opérée par les volailles pour leur alimentation et le couvert s’est homogénéisé par l’augmentation du pourcentage de la biomasse des cypéracées dans la biomasse totale. Cette famille peu appétible pour les volailles s’est ainsi étendue sur toutes les placettes pâturées. Discussion. Le pâturage des volailles, des oies en particulier, s’est révélé être une méthode efficace pour la maîtrise de l’enherbement en verger. Cependant, dans le cas d’une forte proportion d’espèces non appétibles dans la strate herbacée, d’autres méthodes de désherbage devront être combinées. L’installation d’une couverture herbacée composée d’un mélange de plantes de couverture adaptées à l’association verger et volailles ainsi qu’une meilleure gestion de la rotation des animaux devront être envisagées pour optimiser cette technique.
Seasonality and range of fruit fly (Diptera: Tephritidae) host plants in orchards in Niayes and the Thiès Plateau (Senegal)
- Ousmane Ndiaye, Jean-François Vayssieres, Jean Yves Rey, Saliou Ndiaye, Papa Madialéké Diedhiou, Cheikh Tidiane Ba, Paterne Diatta
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Introduction. Senegal produces up to 150,000 t of fruit, of which 60,000 t are mangoes. Fruit production is important for the Niayes region, where 60% of total production is of mangoes, with citrus production coming next at 24%. Mango losses have become more substantial since the arrival of Bactrocera invadens in Senegal. The pest population increases in the mango ripening period, but little is known about its secondary hosts. Materials and methods. Fruits of cultivated and wild plants were collected regularly from April to December 2008 inside and around 19 orchards in eleven localities in the Niayes and Thiès areas in Senegal. The samples were monitored to identify any fruit flies present so that a list of host plants could be compiled. For mango, the study focused on establishing the influence of certain parameters such as the variety, the fruit size, the color, the flowering pattern and the physiological levels of infestation due to B. invadens and Ceratitis cosyra. Orchards were classified either as traditional (many mango varieties and many fruit species grown together in a stand) or intensive (fields of monovarietal mango trees), according to their composition and how they were managed. Results and discussion. A total of 663.2 kg of fruit, including those of 24 mango varieties, 13 citrus species with five lime varieties, two orange varieties and four pomelo varieties along with other cultivated and wild plants, were sampled both as fallen fruit and from the trees. Traditional orchards were more infested than the modern ones. B. invadens was significantly dominant over the other flies emerging such as C. cosyra, C. capitata, C. punctata, C. bremii, Bactrocera cucurbitae, Capparimyia bipustulata, Carpomyia sp. and Dacus sp. B. invadens was found on the 24 varieties of Mangifera indica, the 13 citrus species, and the other cultivated plants and wild plants sampled. Some host plants supported a relatively high level of fruit flies before the mango ripening period. Mangifera indica was infested principally by B. invadens and C. cosyra. C. cosyra was significantly present on the first fruit trees to flower, mostly in early varieties, while B. invadens infested all the varieties whatever the fruit development stage, the color, or the flowering pattern. Conclusion. Because of the host plants' diversity and varieties the traditional orchards were more infested than the modern ones. The management of this pest needs an Integrated Pest Management system based on a back-to-basics study of the infesting fruit flies, existing parasitoids and their hosts.