Climatic risk zoning for potential occurrence of cacao moniliasis disease in Northeastern Brazil under the influence of ENSO phases

Abstract

Air temperature and relative humidity are the main drivers of many fungal diseases, such as moniliasis (Moniliophthora roreri), which affects cocoa production worldwide. This disease occurs in some Latin American countries; however, it has not yet occurred in Brazil. Moniliasis could cause serious damage to the Brazilian cocoa production if present in the country. Therefore, to know the risks of moniliasis to cocoa production in the largest Brazilian producing region, in the state of Bahia, this study investigated the climatic favorability for the occurrence of this disease in this state, by defining and mapping the climatic risks and by assessing the influence of El Niño Southern Oscillation (ENSO) phases on it. Historical daily temperature and relative humidity data (1988–2018) from 28 weather stations of the national weather network in the state of Bahia were obtained. The risk index for cocoa moniliasis occurrence (RICM) was determined, based on the number of days five levels of favorability. Spatial interpolation of seasonal and annual RICM was done through a multiple linear regression method using latitude, longitude, and altitude as predictor variables. The maps showed a high spatial and temporal RICM variability in the state of Bahia, with the highest risk for moniliasis occurrence in the eastern part of the state, where most producing areas are located. The ENSO phase showed to influence cocoa moniliasis occurrence, with the years with a transition between El Niño and Neutral phases being the most critical for this disease in majority of assessed locations. These results show that cocoa producers in the state of Bahia, Brazil, should be concerned with moniliasis occurrence as a potential disease for their crops, mainly in the traditional producing regions and when ENSO is in a transition from El Niño to neutral.