Citrus postbloom fruit drop risk in Southern Brazil as influenced by different El Niño Southern Oscillation (ENSO) phases

Abstract

Citrus postbloom fruit drop (PFD) disease causes large yield losses in orchards, when flowering coincides with intense and prolonged rainfall. Thus, studies related to models that predict the climate effect on PFD are of the utmost importance as they can improve disease control efficiency mainly when considering climate variability, which is mostly caused in Brazil by El Niño Southern Oscillation (ENSO) phases. The objective of this study was to assess the effect of the ENSO phases on PFD in different regions in Southern Brazil aiming to allow a better disease management. For that, weather data of 67 years (1950 - 2016), of five regions in São Paulo state: Bebedouro, Descalvado, Piracicaba, Itapetininga, Santa Cruz do Rio Pardo, and one in Paraná (Maringá), were employed to estimate PFD incidence, based on a phenological-climatological model. The results indicated that there is no clear consensus about the ENOS influence on PFD incidence in citrus in the assessed regions. El Niño years, in Itapetininga, and El Niño and La Niña years in Descalvado are those with higher PFD incidence. For the other assessed locations, no differences were observed for PFD between ENSO phases. When considering the general PFD incidence, differences were observed only between Bebedouro, with the lowest incidence (32.2%), and Itapetininga and Descalvado, where incidence reached 51.2% and 49.5%, respectively.