Black Leaf Streak Disease (BLSD), caused by the fungal pathogen Mycosphaerella fijiensis, is the most important foliar disease affecting banana production worldwide, reducing fruit weight and fruit aptitude for conservation. With growing concerns about environmental preservation and stricter legislation, alternatives to chemical control for BLSD are an important challenge, especially in the French West Indies. These new approaches include various agronomical practices that could help reducing disease development, and its impact on bunch weight and fruit conservation. Designing new cropping systems without fungicide control of BLSD implies an integrated strategy and a combination of these practices. To understand better the relationships between leaf spots diseases and fruit conservation, Cavendish bananas were grown in different situations in Cameroon, Guadeloupe and Brazil. These experiments showed that a signal from diseased leaves triggers a direct reduction in banana green life duration, and that this signal might be stopped through the elimination of diseased leaves. Lately, a new prototype of cropping system has been evaluated in ecological conditions unfavorable to BLSD (in Dominican Republic), combining practices that would control disease cycle and the reduction of crop losses. In such conditions, even if bananas were harvested with a very low leaf surface, green life of the fruit proved to be acceptable for export, thanks to an adequate and regular pruning of the infected leaves. This result questions the usual threshold of 4 to 5 leaves required at harvest time for bunches as acceptable for exportation. However, variable losses (10-15%) in fruit weight were observed. This prototype should be now evaluated in epidemiological situations more favorable to disease development. New practices might also be associated in these conditions, like the introduction of biodiversity (mixtures of species) or the use of plant defense stimulators. (Resume d'auteur)

Introduction. Black Leaf Streak Disease (BLSD) is the most important foliar disease affecting banana production worldwide. A forecasting system has been developed and implemented in various countries aiming at optimal control of BLSD through minimum applications of fungicide. In Dominican Republic, favorable dry climatic conditions contrast with serious organizational issues for BLSD control. Our objective was to evaluate the adaptation of this forecasting strategy in these specific conditions. Materials and methods. Fungicide resistance analyses were carried out in the northwestern region of Dominican Republic, in order to determine the appropriate spectrum of systemic fungicides for the forecasting strategy. Three field experiments were set up on commercial farms where disease evolution was monitored every week, on reference plots, in order to decide the pertinence of fungicide applications. Results. Fungicide resistance to QoI fungicides and strong sensitivity reduction to DMI (Demethylation Inhibitor) fungicides were detected in all farms. In spite of these limitations in the use of some fungicide groups, disease control was achieved with a limited number of fungicide applications (6-9), as compared with 13-26 applications in most commercial farms of Dominican Republic over the same period. Discussion. The calculation of an indicator of the efficiency of the chemical control confirmed the potential of the forecasting strategy, underlining the influence of crop management as well as the neighboring environment of the farms on its efficiency. The requirements for further generalization of this system to commercial farms of this country are discussed.

Black leaf streak disease (BLSD) is considered as the most destructive foliar disease of bananas and plantains. The disease is due to a fungus, Mycosphaerella fijiensis, spread by air and rain. Due to its recent and rapid worldwide invasion and its presence in the northern Caribbean islands since 90's, the risk of introduction in the Lesser Antilles was high. To prevent and/or to detect as early as possible the presence of the disease, scientific and technical efforts were deployed to set up, in the Lesser Antilles, some BLSD epidemiological surveillance networks in the framework of Caribbean Sustainable Banana Project. Since 2010, the activities consisted in different and complementary activities : (i) regional trainings on the BLSD diagnosis were organized by CIRAD and allowed to the still BLSD-free countries (St Vincent, St Lucia, Martinique, Dominica and Guadeloupe) to set up national BLSD vigilance and surveillance networks ; (ii) early official diagnoses were realized in the 5 countries ; (iii) the BLSD spatiotemporal spread was followed in each newly detected allowing to brake its expansion and to optimize control method particularly in bananas vitroplants nurseries and in export bananas plantations ; these surveillance completed with a modeling approach suggest that the invasion duration depends on the numbers of introductions, the efficacy of control methods and the spatial structure of bananas productions ; (iv) the reconstruction of the history invasion in the Caribbean through the molecular analyses of 1800 pathogenic isolates collected in 20 countries suggest the occurrence of 2 invasion pathways and two modes of introduction (human-mediated and natural introductions). All these BLSD epidemiological-surveillance networks in the Caribbean have allowed to detect as early as possible the presence of the disease in 5 countries of the Lesser Antilles and at present allow optimizing control practices. (Resume d'auteur)

With growing concerns about environmental preservation, alternatives to chemical control for black leaf streak disease are an important challenge. Agronomical practices allow reducing disease development, and its impact on fruit production (fruit weight and green life duration). Two hectares of Cavendish banana were grown in the dry climatic conditions of Dominican Republic, without any chemical application during two years. In spite of very low leaf surface at harvest time, green life of the fruit proved to be over 35 days, over than the acceptable duration for exported fruit. Impact on fruit weight was limited but needs to be confirmed by further experiments, in climatic situations more favorable to disease development. (Resume d'auteur)

The Banana leaf spot diseases are a major constraint in most large production areas, resulting in very significant losses in the absence of suitable control system (Stover, 1986;Stover & Simmonds, 1987).There are two major impacts of the disease on the production.Photos credit: CARBAP (J.Ngando) Photo 2. Very severe attack of BLSD on a banana plant with a bunch Photos credit: CARBAP (J.Ngando) Photo 3. Early ripening of the fruits due to severe attack of BLSD www.intechopen.com

Introduction. Black Leaf Streak Disease (BLSD) is regarded as the most economically important threat that the banana industry has to face. Effectively, this foliar disease affects leaf photosynthesis but, above all, reduces the greenlife of fruits, that cannot be exported in cases of severe infestation. Main characteristics of Black Leaf Streak Disease. More than 20 Mycosphaerella species have been described on bananas. Leaf spot diseases of bananas are caused by some species of this complex, of which M. fijiensis (BLSD) and M. musicola (Sigatoka disease) are the most important. M. fijiensis is an invasive species that has totally replaced M. musicola in most banana-exporting countries, which was conducive to increasing difficulties in banana leaf spot control. BLSD causes increasing difficulties for control. Since all banana cultivars grown in the banana industry are highly susceptible to BLSD, the control of this disease relies on aerial applications of fungicides according to either systematic frameworks (mostly contact fungicides) or forecasting strategies (mostly systemic fungicides). In a banana-exporting country where M. fijiensis has been reported, BLSD control becomes increasingly more difficult. This evolution is essentially due to the rapid emergence of fungicide resistance, and is conducive to a significant increase in the cost of disease control but, above all, to increasing negative environmental effects. Challenges for the banana industry. Because of the rapid adaptation of M. fijiensis, the banana industry must be prepared for significant evolution. We propose various parameters that should be monitored at different levels (disease assessment parameters, evaluation of chemical control efficiency, global evaluation of BLSD economic incidence) to rationalize such evolution. The modelization of BLSD effects on bunch mass and greenlife should enable defining acceptable disease thresholds and optimizing bunch weight and harvest stage according to agronomic practices. On the other hand, fungicide use is conducive to significant environmental impact and must be limited. Forecasting strategies should be used wherever systemic fungicides are still efficient. Finally, the predominance of a unique type of susceptible cultivar is unsustainable and the recourse to resistant varieties in an integrated strategy is undoubtedly the future of BLSD control.

Introduction. This protocol aims at monitoring the development of Black Leaf Streak (Mycosphaerella fijiensis Morelet) disease of banana plants in order to control this disease with a minimum of fungicide applications. A good timing of fungicide application will result in lower cost of control, lower risk of fungicide resistance and lower environmental negative impact. The principle, key advantages, starting plant material and expected results are presented. Materials and methods. Details of the six steps of the protocol allowing banana plot preparation, data collection, stage of evolution of the disease ( SED) calculation, and timing of fungicide applications are described. Possible troubleshooting is mentioned. Results. Weekly observation of selected banana plants allows filling in a data sheet used for the calculation of the SED. A graphic representation of the weekly evolution of this SED can then be used for timing of fungicide spraying decisions.