Yellow Sigatoka (Mycosphaerella musicola Leach) is one of the most serious banana diseases in Brazil, it can cause yield losses higher than 50%. The main control method has been based on spraying fungicides. The use of a monitoring system able to indicate the appropriate moment for spraying fungicide, is a very important alternative to rationalize its uses. This work aimed to defining a Total Sum value for the biological forecasting system that allows to reduce the number of annual fungicide applications needed for Yellow Sigatoka control in Recôncavo Baiano Region. The work was carried out at Embrapa Cassava & Fruits, of the Brazilian Agricultural Research Corporation - EMBRAPA , located in the Municipality of Cruz das Almas, State of Bahia. Eight treatments were evaluated: six of them using pre-established Total Sum values of the biological forecasting system (1000; 1300; 1600; 1900; 2200 and 2500), the sistematic disease control by fungicide spraying every 21 days, and the control treatment without spraying. The treatments consisted of eight plots containing 48 plants each, of the cultivar Grand Naine. Every week, ten plants of each treatment were evaluated for rate of leaf emission and disease incidence in the leaves 2, 3 and 4, in order to determine the highest degree of lesion intensity. The weekly data were used to calculate the respective Total Sum values thus indicating the necessity or not of fungicide application (propiconazole, 3 mL, plus mineral oil, 1 L). At harvest, data on production and disease severity were taken. Only three of the evaluated treatments were statistically different from the control treatment without sprayings: fungicide application every 21 days; fungicide application when the Total Sum reached 1,300; and fungicide application when the Total Sum reached 1,600. Considering the yield obtained and the number of fungicide applications required during the crop cycle, it is concluded that, for the Recôncavo Baiano Region, the application of the biological forecasting system for chemical control of Yellow Sigatoka should be performed when the Total Sum reaches 1,600. This system allowed a decrease in the number of fungicide application from thirteen to eight per year, that means 40% less fungicide used without decreasing yield.
banana; disease; Pseudocercospora musae; Mycosphaerella musicola
