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Elaboration of an Early Quantification Method of Quiescent Infections of Colletotrichum musae on Bananas

Colletotrichum musae, the causal agent of banana anthracnose, forms quiescent infections on the surface of the fruit that lead to necrosis at maturity. This work was conducted to determine a practical way to quantify the inoculum level that is economically practicable for routine use and applicable to immature fruit, so that it can be used as a method of early prediction and subsequent decision support. The method that has been developed is based on treating the fruit with 1,200 μl of ethylene per liter for 24 h at 25°C. The fruit are then kept at 32°C for 5 days, maintaining the ethylene concentration, so that conditions are optimal for revealing the disease. The technique can be used on fruit whose age is 5 to 6 weeks after inflorescence emergence. A high CO₂ concentration has an inhibitory effect on the development of lesions. The importance of the ethylene treatment on fruit maturation and breaking of appressorium dormancy is discussed, together with potential applications.