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Originally from Asia, this small fly recognizable by its yellow spots on the thorax was first detected in 2004 in Casamance, in the south of Senegal, before continuing its invasion throughout the country – especially from May to October, the hot season. rainfall consistent with the mango harvest. A team of CIRAD researchers is trying to understand how it reappears each year, in order to find solutions to this scourge.
With our special correspondent in Casamance
Every week, a team of researchers travels through 28 orchards in lower Casamance to count the flies captured in traps, in order to observe their evolution during the year. Thierry Brévaut, a researcher from CIRAD (Centre for International Cooperation in Agronomic Research for Development) who coordinates the project, takes about sixty from a bottle filled with alcohol and then carries out genetic analyses.
« We will compare DNA sequences between the different orchards, he explains. This will allow us to know how fly populations are formed. Are these flies that come from other countries through the mango trade, but also through the wind. And the third hypothesis is that we locally have populations from which fly populations will be reconstituted. »
The objective is above all to provide the keys to establishing a new strategy for combating the fruit fly. ” If we can manage to understand how these populations are reconstituted, we can know over what geographical extent the fight must be implemented.emphasizes Thierry Brévaut. If the flies come from very far away, it will undoubtedly be a regional strategy that will have to be put in place. Maybe you have to fight well before the mango season, when the populations are very low. ».
The researcher evokes the sterile insect technique, where millions of irradiated males are released into the wild in order to reproduce with females – without producing offspring.
Helping growers eradicate the fly
But in the meantime, Aliou Djiba, president of the association of young farmers from Casamance AJAC Lukaal, calls for more state support: “ The State has found the means to give us products that have really given convincing results, especially wasp releases. Biological control has given results. All the same, the state must help us to really intensify this fight, to make it general. Because the producer does not have so many means. »
Boubacar Seydi, president of the mango sector innovation platform, is campaigning for the professionalization of Casamance orchards: ” In good agricultural practice, farmers are advised to maintain the orchards because the fly breeds on the mango. This is the reason why we ask to pick up everything, we bury it. We clean the whole orchard with pruning, we treat. But the problem, it’s that we don’t have a modern classic form of mango production. »
Since 2015, ECOWAS has been trying to harmonize the methods of combating this scourge at the sub-regional level
► To listen or read: Senegal: the fruit fly, scourge of mango producers (1/2)