Agroclimatic zoning: Brazilian regions favourable for citrus postbloom fruit drop

Abstract Citrus production is a significant agricultural activity in Brazil, the world's largest producer and exporter of orange juice. However, this production faces phytosanitary challenges, including postbloom fruit drop (PFD) caused by fungi of the genus Colletotrichum . The development of this disease is associated with climate conditions, such as temperature and leaf wetness duration (LWD). Citrus production in Brazil has recently migrated to regions with no records of greening disease (caused by Candidatus Liberibacter spp.), and these areas require assessments of the impacts of other diseases. Such assessments are essential to identify phytosanitary risks and implement effective management strategies to ensure sustainability and support the expansion of citrus production. The objective of this study was to conduct agroclimatic zoning for PFD using climate variables, such as mean temperature and LWD. The analysis covered the entire Brazilian territory, using data from 1989 to 2020, collected from the NASA/POWER platform. The areas were classified climatically as unfavourable, relatively favourable, or highly favourable. The results revealed that the North and Northeast regions are highly favourable for the development of the disease year-round, while the South, Southeast and Central-West regions present lower risk during the winter. The risk of disease occurrence in the main citrus-producing areas of the Southeast region is higher from January to March, and August to December. The analysis indicated that emerging citrus-producing areas exhibit higher climatic suitability from January to May. This study highlights the importance of management strategies, such as the use of fungicides and climate monitoring, to mitigate the impacts of PFD.