Progresso da sigatoka-negra (Mycosphaerella fijiensis) em bananeiras após a emissão do cacho no Município de Cáceres, Mato Grosso-Brasil

The black sigatoka, caused by Mycosphaerella fijiensis may cause 100% of yield losses in susceptible cultivars. The objective of this work was to evaluate the progress of the black sigatoka in banana plants after the bunch emergence, in the district of Caceres, Mato Grosso State - Brazil. The experiment was carried out from February to December 2004, in banana cultivars "Grande Naine" and "Maca", as well as plantain cultivar Farta Velhaco (Terra group). For each cultivar, the severity of black sigatoka was evaluated every fifteen days in all leaves of five previously marked plants, using a diagrammatic scale. From the collected data in the field, were computed: The disease severity in the leaf number 10 and the functional leaves number. It was considered as functional leaf the healthy leaves and those with up to 15% of lesioned foliar area. The temperature and air relative humidity data were recorded by an electronic apparatus installed in the area, while pluvial precipitation data were taken from the meteorological station of Caceres, 12 km away. The climatic conditions were suitable for the black sigatoka during throughout the year and the plant cultivars "Maca", "Grand Naine", and "Farta Velhaco" after bunch emission, had total lost leaves before full development of fruits. These caused damages in the first semester reached 100% of losses in the marketable production.