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Annual population dynamics of mango fruit flies (Diptera: Tephritidae) in West Africa: socio-economic aspects, host phenology and implications for management
- Jean-François Vayssières, Antonio Sinzogan, Appolinaire Adandonon, Jean-Yves Rey, Elhadj Oumar Dieng, Koumandian Camara, Morodian Sangaré, Sylvain Ouedraogo, N’klo Hala, Adama Sidibé, Youssouf Keita, Guy Gogovor, Sam Korie, Ousmane Coulibaly, Cinthia Kikissagbé, Alliance Tossou, Max Billah, Koffi Biney, Oswald Nobime, Paterne Diatta, Robert N’Dépo, Moussa Noussourou, Lanciné Traoré, Symphorien Saizonou, Manuele Tamo
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Introduction. Losses in West African commercial mango orchards due to fruit fly infestations have exceeded 50% by the middle of the crop season since 2005, resulting in considerable income loss for the growers. Materials and methods. In 2009, weekly monitoring of adult fruit fly species of economic significance was carried out in eight West African countries at 12 sites across five agro-ecological zones: (i) Humid Forest, (ii) Guinean savanna, (iii) Southern Sudan, (iv) Northern Sudan, and (v) Sahelian. Trapping was performed using methyl eugenol and terpinyl acetate in 288 Tephri-traps, targeting Bactrocera invadens and Ceratitis cosyra. Results. The data showed that B. invadens was present throughout the year in the Forest zone, abundant for 7 months, with a peak in May at the end of the mango season, C. cosyra being totally absent. In the Guinean savanna zone, B. invadens was abundant for 6-7 months, with a peak at the beginning of June coinciding with the season, with a few C. cosyra. In the Southern Sudan zone, B. invadens was abundant for 6 months, with a peak in mid-June during the season, C. cosyra peaking in April. In the Northern Sudan zone, B. invadens was abundant for 5 months, with a peak at the end of June at the end of the season, C. cosyra peaking in May. In the Sahelian zone, B. invadens was abundant for 4 months, peaking in August during the season, C. cosyra peaking just before. These preliminary results showed that the exotic species, B. invadens, was present at high levels [mean peak of 378 flies per trap per day (FTD)] in all agro-ecological zones, while the native species, C. cosyra, preferred the drier zones of West Africa, with lower population levels (mean peak of 77 FTD). Conclusion. Detection trapping of male flies with parapheromones is a useful indicator of field population levels and could be used to deploy control measures (IPM package) in a timely manner when the Economic Injury Level is reached. Control strategies for these quarantine mango fruit fly species are discussed with respect to agro-ecological zones and the phenological stages of the mango tree.
Distribution and host plants of Bactrocera cucurbitae in West and Central Africa.
- Jean-François Vayssières, Jean-Yves Rey, Lanciné Traoré
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Introduction. The data on Bactrocera cucurbitae collected over a large area of West Africa for around the past ten years enables us to make a synthesis, since this economically significant species is now widespread. Fruit samples were collected in the course of various trips to Africa; we focused on looking for the melon fly, B. cucurbitae (Coquillett). Equipment and methods. The Tephritidae were captured by means of trapping the adults and collecting holed fruit containing larvae. The fruit samples were taken from Cucurbitaceae found in the sub-region, and from other plant families hosting melon fly larvae. Fruit holed by flies were collected from untreated orchards and taken to the laboratory to be weighed, counted and classified by species, variety, date and location. The larvae collected metamorphosed into pupae. After hatching from the pupae, the adults were recovered. Results and discussion. The samples taken enabled us to determine the distribution of B. cucurbitae in West Africa; this species was found in Benin, Burkina Faso, Cameroon, Côte d’Ivoire, Guinea, Mali, Niger and Senegal. The fruit collected in these countries enabled us to draw up a list of B. cucurbitae host plants in these regions; besides Cucurbitaceae, there were two Anacardiaceae species, two Rutaceae species, one Annonaceae species, one Solanaceae species and one Oxalidaceae species. There were four economically important fruit species among them. Unlike Reunion, where the dietary pattern of the melon fly is oligophagous, in West Africa it appears to be polyphagous instead. Conclusion. The data collected from B. cucurbitae host plants is subsequently to be validated, and then refined by quantitative analyses for the different West African countries.
Vers une lutte contre la cercosporiose des agrumes en Guinée
- Mamadou Tidiane Sankaréla Diallo, Mahmoud Camara, Mastan Youssouf Diane, Alpha Souleymane Bah, André Moriba Pivi, Lanciné Traore
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Introduction. L'apparition de la cercosporiose due à Phaeoramularia angolensis en 1993 en Guinée constitue de nos jours l'un des facteurs limitants de la culture des agrumes dans ce pays. Le manque de connaissance sur la sensibilité, vis-à-vis du pathogène, des espèces ou variétés d'agrumes présentes localement freine la relance projetée pour cette culture. Face à cet enjeu, des études sur la sensibilité in situ et des essais de contrôle chimique de la maladie ont été entrepris. Matériel et méthodes. Des agrumes en collections et en plantations villageoises ont été suivis de 1995 à 1999 dans les principales régions productrices d'agrumes de Guinée afin d'évaluer la sensibilité à Phaeoramularia angolensis d'une soixantaine de variétés. En complément, un essai de lutte chimique a été mené en 1999 afin de définir les doses et fréquences de traitements à recommander aux planteurs pour contrôler la maladie. Le taux d'organes atteints et les pertes de production dues au pathogène ont été évalués. Résultats et discussion. Les sensibilités ont varié suivant les sites mais surtout en fonction des espèces et de leurs variétés. Presque tous les orangers et tous les tangelos et pomelos se sont montrés sensibles à très sensibles à la maladie avec des taux de dépréciations de l'ensemble de la production (feuilles et fruits) souvent supérieurs à 30 %. Les taux de sensibilité des mandariniers ont été plus contrastés avec des variétés tolérantes (Ponkan) à très sensibles (Hansen). Les tangors, citronniers, limettiers, kumquats et pamplemoussiers se sont révélés tolérants dans tous les sites à la seule exception du limettier Tahiti et du citronnier Meyer au-dessus de 800 m d'altitude. Lors de l'essai de lutte chimique, la dose de 100 g de matière active $\cdot$ 100 L-1 d'eau appliquée tous les 10 j a permis d'élever en moyenne à près de 90 % le taux de fruits potentiellement commercialisables. Par ailleurs, la rentabilité des vergers a décru rapidement dès que le taux d'attaques des fruits a été supérieur à 20 %. Conclusion. Nos résultats montrent que de nouvelles recherches entreprises dans le contexte actuel de l'agrumiculture guinéenne pourraient permettre de répondre aux problèmes de stratégies de lutte à adopter, de produits, doses ou périodes à recommander et de variétés à promouvoir dans le pays.