-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.France / Musa / disease control / fungal diseases / Mycosphaerella fijiensis / resistance to chemicals La Maladie des Raies Noires défie l'industrie de la banane.Résumé -Introduction. La Maladie des Raies Noires (MRN) est la plus grande menace à laquelle est confrontée l'industrie de la banane. En effet, cette maladie foliaire affecte la photosynthèse des bananiers mais, surtout, elle entraine une réduction du potentiel de conservation des fruits qui ne peuvent être exportés lorsque les bananiers sont sévèrement atteints. Principales caractéristiques de la MRN. Plus de 20 espèces du genre Mycosphaerella ont été décrites sur le bananier, mais les cercosp...
A biological forecasting system to control Black Leaf Streak disease of bananas and plantains.Abstract --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. Résumé --Introduction. Ce protocole permet de quantifier le développement de la maladie des raies noires (Mycosphaerella fijiensis) du bananier pour contrôler chimiquement cette maladie avec un minimum d'applications de fongicide. Une bonne programmation de l'application des molécules fongicides permettra de diminuer le coût du contrôle, le risque de voir apparaître des souches de M. fijiensis résistantes aux fongicides, et l'impact négatif des traitements sur l'environnement. Le principe, les principaux avantages, le matériel végétal de départ, et les résul-tats attendus de la méthode sont présentés. Matériel et méthodes. Le détail des six étapes de réalisation du protocole permettant la préparation de parcelles en bananeraie, la collecte de données, le calcul de l'état d'évolution de la maladie (EEM) et la programmation de l'application des fongicides est décrit. De possibles problèmes sont évoqués. Résultats. L'observation hebdomadaire des bananiers choisis permet de remplir une fiche de données utilisée pour le calcul de l'EEM. Une représentation graphique de l'évolution hebdomadaire de cet EEM peut être alors utilisée pour programmer l'application des fongicides.Cameroun / Musa sp. / méthode / contrôle de maladies / Mycosphaerella fijiensis / avertissement agricole
Introduction. Citrus leaf and fruit spot due to Phaeoramularia angolensis [De Carvalho & Mendes] P.M. Kirk represents a serious production constraint in tropical Africa. Disease expression may vary greatly from one location to another. Materials and methods. Disease development was studied on young seedlings of grapefruit (Marsh cultivar) inoculated with a conidia suspension and transferred to eight locations at (80 to 1250) m elevation. Temperature (T) and relative humidity (RH) were recorded on the sites during the work. Results and discussion. Disease incidence increased with altitude. The Nyombe Station (80 m elevation, Taverage > 25°C with Tmax above 30°C and RHaverage < 80%, with RHmin often below 60%) was far less conducive to disease development than the rest of the locations, which experienced cooler and more humid climatic conditions (Tmin < 20°C and RHmin > 60%). Conclusion. This study provides preliminary information on characterization of regions that may be invaded by P. angolensis. The work should be pursued, including different ecological situations, to enable the mapping of the risk of this threat.
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