Spatiotemporal dynamics of Fusarium wilt of banana caused by Subtropical Race 4

Historically, Fusarium wilt of banana (FWB) caused by Fusarium oxysporum f. sp. cubense (Foc) has rendered hectares of banana unusable in Central and South America. In 2019, tropical race 4 (TR4), the most virulent race of Foc, was detected in South America and its spread to the main banana-producing regions is a matter of time. This study investigates the spatio-temporal dynamics of FWB caused by subtropical race 4 (SR4) and its relationship with environmental features, aiming to provide a basis for epidemiologically-based mitigation actions to contain TR4. One banana cv. ‘Maçã’ (AAB) field was established in 2017 in Minas Gerais, Brazil. Bimonthly assessments of incidence were conducted between 2017 to 2020. Weather variables were also recorded. The spatial pattern was studied using quadrat- and distance-based methods. Temporal analyses were based on epidemiological models fitted to disease progress curves. Average values of weather variables were estimated for intervals of 2-, 4-, 6-, and 8-weeks before a given assessment date seeking for any correlation with FWB incidence and absolute disease progress rate. The first foci were detected six months after planting and were randomly distributed across the field The spatial pattern changed to aggregated when FWB incidence increased (maximum of 43%). The FWB progress curve had a sigmoidal-shape and the Gompertz model provided the best description of the temporal dynamic of FWB. Increases in the rate of progress of FWB were correlated with precipitation four weeks before the evaluation. Mitigation actions based on the spatio-temporal epidemiology of SR4 in highly susceptible cultivars might contribute to prevent total crop losses and the expansion of FWB into non-infested regions.