Résumé
Mycosphaerella foliar diseases, Black Leaf Streak and Sigatoka diseases caused respectively by Mycosphaerella fijiensis and M. musicola, are by far the main parasitic constraints for export bananas. They result in substantial necrosis of the foliage and consequently yield loss, but - most importantly - in immature ripening that renders bananas unfit for export. In the absence of commercial resistant varieties, banana exports can only be achieved through intensive chemical control. In most countries, fungicides are applied systematically following a fixed-schedule treatment programme (40-60 applications/year) to protect the young leaves against infection. In some places, forecasting systems are used to schedule treatments in function of the stage of evolution of the disease (5-14 treatments/year). In all countries chemical control has to face increasing difficulties in terms of efficacy, cost and environmental impact. This situation results mainly of two major events: (i) the development of fungicide resistance to systemic fungicides that lead to a systematic use of protectants and (ii) the evolution of the legislation which becomes increasingly restrictive. New alternatives that must be associated with basic prophylactic measures such as the mechanical ablation of lesioned leaves are needed for a sustainable control of these diseases. They are presented as (1) short-term solutions: implement the forecasting strategy where it is feasible or introduce fungicides with low negative environmental effect where this forecasting strategy is impeached by fungicide resistance; (2) mid-to-long-term solution: develop and introduce resistant cultivars in the cropping system. (Résumé d'auteur)