Risk assessment of <i>Fusarium oxysporum</i> f. sp. <i>cubense</i> Tropical Race 4 in São Paulo’s Vale do Ribeira using a survey-based framework

Abstract Background: Fusarium wilt of banana (FWB), caused by Fusarium oxysporum f. sp. cubense (Foc) Tropical Race 4 (TR4), is one of the most severe threats to global banana production. The confirmed presence of Foc TR4 in neighboring countries (Colombia, Peru, and Venezuela) heightens the risk of its introduction into Brazil, with potentially serious socio-economic impacts. Methods: This study assessed the risk of Foc TR4 establishment and spread on 387 banana farms in the Vale do Ribeira region, São Paulo, using survey data on geographic (location), biosecurity, and phytosanitary categories. Each of 25 questions was assigned a different weight (0 to 5 points) defined by a panel of three experts based on the theoretical impact of each response in the respective category. A normalized risk index (0–1) (total points divided by maximum points) was calculated for each farm. Results: Results showed that most farms were located near roads, urban areas, and watercourses, and clustered within banana-producing zones, conditions that increase the risk of pathogen entry and spread. Biosafety adoption was critically low: 95% of farms lacked disinfection protocols, fencing, or visitor controls, and only 26% provided training on pests or diseases. Conventional propagation practices and the use of shared equipment further elevated phytosanitary risks. Although awareness of FWB symptoms was high, management of Foc Race 1 (R1) remained reactive, relying on replacement of R1-susceptible cultivars such as Prata (Pomme, AAB) and Maçã (Silk, AAB) with the R1-resistant but TR4-susceptible Cavendish (AAA). The overall risk ranged from 0.22 to 1.00 (mean = 0.63). When stratified by question category, the mean risk values were: location (0.70), biosecurity (0.66), and phytosanitary condition (0.40). Spatial analyses revealed high-risk clusters associated with proximity to highways, rivers, and urban areas. Conclusions: Based on these findings, mitigation strategies are proposed, including the implementation of biosecurity protocols, producer training, and regional contingency planning. This study provides technical and spatial evidence to support plant protection services in deploying preventive actions in one of Brazil’s most important banana-producing regions.