período de incubação de Guignardia citricarpa em diferentes estádios fenológicos de frutos de laranjeira 'Valência'

Abstract

Citrus black spot (CBS), caused by Guignardia citricarpa, causes lesions on fruit that depreciate them for the domestic market and restrain them for export. The long susceptibility period in fruit, in addition to the occurrence of latent infection, diffcult the understanding of CBS incubation period. The aim of this study was to determine the incubation period of CBS by inoculating fruits of 'Valencia' orange at different phenological stages. Conidia suspensions of G. citricarpa at different concentrations (103, 104, 105 and 106 conidia mL-1) were inoculated in fruit of different diameters (1.5, 2.0, 2.5, 3.0, 5.0 and 7.0 cm). The relationship of CBS incubation period with fruit diameter was polynomial negative. The average incubation period for 3 cm fruit was over 200 days, while fruit which were greater than 5 cm in diameter had an average incubation period of less than 100 days. CBS incubation period is therefore variable and depends on the phenological stage in which the fruit have been infected. The concentration of G. citricarpa conidia did not interfere with the incubation period of the disease.