During fruit development, banana accumulates starch, which is then degraded during ripening. This degradation provides precursors for sucrose and volatile compounds, responsible for sweetness and the characteristic aroma of the fruit. Starch metabolism may be influenced by the phytosanitary status of the plant. Black leaf streak disease (BLSD), caused by the pathogenic fungus Mycosphaerella fijiensis, is one of the most important diseases of banana. BLSD causes yield loss and has a strong effect on postharvest fruit quality. The aim of this study was to evaluate differences between the starch and sugars contents of fruits from a BLSD-infested plot and a fungicide-treated (control) plot. Starch and sugar contents were determined in fruits at two different physiological ages, i.e., early and late fruit harvest. Results show that BLSD may affect starch metabolism in a way similar to the advance of physiological age.