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Abstract

A study was carried out in 14 localities of Baru, Chiriqui, to determine the grade of loss due to Sigatoka Negra (Mycosphaerella fijiensis var difformis). There was trying to determine the influence of the disease over the amount of functional leaves of plantain's plant and a classification of the area by the grade of intensity of the disease in each one. 120 plants in the blossom stage were located in eight production's nucleus with a monthly sampling using the modified International method of Stover and Dickson. The critical months in which the disease reduced the amount of functional leaves were November and February. The localities near to the sea (Chiriqui Viejo and Manaca) presented the highest indexes of functional leaves meanwhile Cuervito and Progreso presented the lesser indexes. During the year of the study, it was determine that the rainfall was directty related to the grade of influence of the disease. Nearby to accumulated rainlfall of 1,890 mm, the number of functional leaves in the plants was about seven, which was the minimum number of functional leaves to produce a good bunch of plantains.