Epidemiologia da mancha graxa dos citros (Mycosphaerella citri) no Recôncavo Baiano

Abstract

The citrus industry, activity of socio-economic relevance in the context of family farming, gives the State of Bahia the second place in the national production ranking.The Recôncavo and Litoral Norte regions are the main cultivation areas. Among the phytosanitary problems, the citrus greasy spot, a fungal disease caused by Mycosphaerella citri can be highlighted. It causes leaf symptoms described as raised, light-brown to black, oily lesions with diffuse margins, surrounded by a yellowish-green border. In areas with relative humidity close to 100% and high temperatures for prolonged periods, the disease correlates with premature defoliation that reduce tree vigor, yield and fruit size, and may cause damage around 5t/ha. This study aimed to characterize citrus greasy spot symptoms, to develop and validate a diagrammatic scale to estimate the severity on leaves, to understand its spatial-temporal dynamics and to determine seasonal defoliation patterns for 'Pêra' and 'Bahia' sweet orange varieties. In 19 municipalities of the Recôncavo region of Bahia, prevalence of 100% was found in orchards with incidence of 100% in plants. Over 15 months, within the period from august 2006 to october 2007 the disease spatiotemporal dynamics was characterized in ten orchards of Cruz das Almas, registering incidence values of 100% in plants and their quadrants and 87% in leaves, with an increasing tendency. The analysis of spectral density showed that incidence varies according to a main three months cycle. The index of dispersion for most of evaluations was statistically similar to or lower than 1. The defoliation pattern was similar among varieties. These results indicate that citrus greasy spot can be characterized in the Recôncavo region of Bahia, as an endemic disease of high prevalence and intensity, with a spatial pattern tending to uniformity.