Winter pruning: option for management against alternaria brown spot (Alteraria alternata f. sp. citri) in Honey Murcott tangor [Citrus reticulata Blanco x C. sinensis (L.) Osbeck]

Abstract

Alternaria brown spot (ABS), caused by Alternaria alternata f. sp. citri, is the main fungal disease plaguing tangerines. The main symptoms are falling leaf and fruit, resulting in the loss of production and quality. The initial symptoms in leaves are characterized by small brown or black spots, surrounded, or not, by yellowish halos. In the fruit, dark cortical patches appear that can easily break. In this study, the winter pruning of the plants was investigated to complementary control of ABS. The experiment was conducted in 10-year-old Honey Murcott tangor plants, where two treatments were applied: pruning in winter and no pruning, using a randomized block design with ten replicates. The treatment of winter pruning was performed before the flowering of the plants (September in Brazil), where the branches were cut close to the trunk, the thicker branches were removed. The chemical control was performed in both treatments. Evaluations of disease severity in fruit were performed using a diagrammatic scale; the disease incidence and area under the disease progress curve (AUDPC) were also calculated. The fruit drop and yield (t ha-1) of the plants were quantified, and the temperature and humidity inside the canopy of the plants were measured. Winter pruning had a positive effect on ABS management since it provided a decrease in incidence, severity, and AUDPC values. Fruit fall was reduced, resulting in greater productivity for Honey Murcott tangor plants. The results confirmed the positive effect of winter pruning on the management of alternaria brown spot.