Necrotic leaf removal: an effective method to limit the green life shortening effects of Sigatoka leaf spot disease in bananas

Banana fruits are harvested and marketed in the green stage. Green Life (GL) is the number of days between harvest and initiation of the ripening process, representing the time available to commercialization. Sigatoka leaf spot disease (SLSD), caused by the fungus Mycosphaerella musicola, is one of the main foliar diseases of banana production that leads to early ripening of the fruit, thus reducing the GL. The aim of this work was to determine whether removal of necrotic leaves could limit the effect of SLSD on fruit GL. Plants were classified according to four SLSD infestation levels, based on estimation of necrotic leaf area at flowering. GL of fruits was measured at 13°C, simulating the storage conditions during shipping, using two different treatments: plants with no leaf removal and plants with necrotic leaves removal (1 month before harvest). Higher SLSD infestation levels were associated with reduced GL values, reaching almost zero for the highest infestation level when leaves were not removed. However, with removal of necrotic leaves, GL increased over that of the control treatment (no leaf removal), and GL reached values greater than 40 days even for the highest infestation levels. Analyses of variance followed by Newman-Keuls tests (5% threshold) were conducted to compare different infestation levels among treatments. The removal of necrotic leaves 1 month before harvest considerably limited and, in some cases, suppressed the effect of SLSD on fruit GL at disease severity levels as high as 45% at flowering. In conclusion, pre-harvest removal of M. musicola-infected leaves represents a simple and effective cultural practice that may facilitate increased production of exportable bananas, when chemical control is not desired, not possible, or not efficient. (Résumé d'auteur