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.

Abstract – Introduction. The susceptibility of banana fruit to crown rot andanthracnose, the two main banana post-harvest diseases, is influenced by many pre-harvestabiotic factors. Mycosphaerella leaf spot diseases (MLSD) of bananas arebiotic pre-harvest factors, which have an influence on fruit physiology. The fruit’ssusceptibility to post-harvest diseases may also be influenced by foliar diseases causedby M. fijiensis, responsible for black leaf streak disease (BLSD), andM. musicola, which causes sigatoka disease (SD). The aim of our studywas to determine the influence of these biotic pre-harvest factors on banana fruit’ssusceptibility to crown rot and anthracnose. Materials and methods. A diseaseseverity gradient was established in two experimental fields (Cameroon for BLSD andGuadeloupe for SD) where, at the flowering stage, six different levels of MLSD severitywere selected. Fruit susceptibility was determined through necrotic surface assessmentsafter artificial inoculation by Colletotrichum musae on the 3rd hand ofharvested bunches. Results and discussion. BLSD significantly influencedbanana sensitivity to crown rot (P < 0.001) but only had a slighteffect on the development of anthracnose ( P = 0.041). SD had no effect(P > 0.05) on banana susceptibility to either post-harvest disease.These results are discussed with emphasis on the influence of variations in thesource-sink ratio on fruit physiology. The influence of BLSD on crown rot disease suggeststhe need to take into account the management of these foliar diseases for an alternativecontrol method of post-harvest diseases through integrated pest management programs.

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 to diagnose under laboratory conditions the main Mycosphaerella spp. pathogens of bananas and plantains. The three pathogens Mycosphaerella fijiensis (anamorph Paracercospora fijiensis), M. musicola (anamorph Pseudocercospora musae) and M. eumusae (anamorph Pseudocercospora eumusae) are, respectively, the causal agents of Black Leaf Streak disease, Sigatoka disease and Eumusae Leaf Spot disease. The principle, key advantages, starting plant material and time required for the method are presented. Materials and methods. The laboratory materials required and details of the thirteen steps of the protocols (tissue clearing and in situ microscopic observations, isolation on artificial medium and cloning of single-spore isolate, in vitro sporulation and microscopic observations of conidia, and long-term storage of isolates) are described. Results. Diagnosis is based on the observations of anamorphs (conidiophores and conidia) which can be observed directly from banana leaves or after sporulation of cultivated isolates if sporulating lesions are not present on banana samples.

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.

Introduction. This protocol aims at (i) analysing the nature of host-parasite interactions (resistance or susceptibility), and (ii) studying the variability of the pathogenicity of different pathogen populations (intra/inter-specific) with regard to both virulence and aggressiveness using artificial inoculation with Mycosphaerella fijiensis or Mycosphaerella musicola on plants and banana leaf pieces. The principle, key advantages, starting plant material and time required for the method are presented. Materials and methods. Laboratory materials required and details of the sixteen steps of the protocol (conidial inoculum preparation, artificial inoculation on banana plants and artificial inoculation on banana leaf pieces) are described. Possible troubleshooting is discussed. Results. Typical symptoms of the different diseases are obtained after artificial inoculation.

Black Sigatoka, caused by the leaf fungus Mycosphaerella fijiensis Morelet, is a major constraint to banana production around the world. In Ecuador, the biggest banana-exporting country in the world, this disease has become increasingly aggressive. This has resulted in more fungicide applications, which have significantly increased costs in production and for the environment. Consequently, many banana growers have shifted to organic production, which produces greater economic returns as a result of higher sale prices. In addition, production costs are lower as no fungicides are applied. These organic bananas receive substantial amounts of organic products. This study describes the black Sigatoka disease and nutrient status in an organic banana plantation and compares it with a conventionally fertilized and fungicide-treated plantation. Black Sigatoka symptoms were evaluated in the vegetative and flowering stages under both production conditions and in vitro conditions. Univariate and multivariate descriptive statistics were used to analyze the parameters. Disease symptoms were more severe in leaves from the organic field than in leaves from the inorganic field, but the nutrient status (soil and foliar) did not differ between the two farms. Banana plants from the organic farm had 12 functional leaves at flowering and eight functional leaves at harvest. Average banana yields were over 40% lower for organic versus inorganic management; however, the average price received for organic bananas was over two times higher. Profit–cost analysis has shown that the organic banana farm was substantially more profitable than the inorganic one during the time period analyzed. These results indicated that bananas can be grown commercially without fungicides, and the lower productivity levels are compensated by higher prices of organic fruits in international markets. In addition, organic production has beneficial impacts on social and environmental issues.

Introduction. Le plantain constitue une importante denrée alimentaire pour de nombreuses populations au sud du Sahara. Sa production dans les systèmes traditionnels de culture par les petits paysans est menacée par la maladie des raies noires, une maladie foliaire due à Mycosphaerella fijiensis Morelet responsable de pertes importantes de récolte. Pour faire face à cette maladie, des hybrides tétraploïdes de type plantain, résistants à la maladie, ont été créés au Cameroun puis sélectionnés à l’issue d’une première phase d’évaluation. Après multiplication végétative, les hybrides ainsi sélectionnés ont été évalués en station de recherche afin de déterminer leurs caractéristiques agronomiques et leur rendement potentiel en conditions de culture semi-intensive. Matériel et méthodes. De 1996 à 2000, trente hybrides sélectionnés ont été évalués, en comparaison avec leurs parents femelles, sur deux cycles de production à la faveur de trois essais mis en place suivant un dispositif expérimental en blocs de Fisher complètement randomisés avec deux répétitions de 10 bananiers chacun. Chacun des bananiers a été étudié à partir de caractéristiques agronomiques portant sur la croissance et la production. Résultats et discussion. Sept hybrides ont été sélectionnés sur la base de leur rendement potentiel élevé, de leur précocité de floraison et de leur pouvoir rejetonnant. Cependant, ce matériel végétal tétraploïde présente plusieurs défauts qui constituent un frein à leur diffusion. Certains de ces hybrides sont utilisés comme produits intermédiaires dans un nouveau schéma d’amélioration variétale au CARBAP.