Display omitted •Phylloplane bacteria were effective in reducing the bacterial blight severity.•Iron and nitrogenate compounds competition explains bacterial blight control.•Disease control ability is not related to antibiosis nor to resistance induction.•Siderophore-producing organisms may lead to a false-positive result for antibiosis. The knowledge of biological control mechanism that provides a significant reduction in disease severity can guide the screening procedures and allow the discovery of new possibilities for disease control. In this study, a reduction of bacterial blight severity, caused by three Xanthomonas axonopodis pv. passiflorae (Xap) strains, was demonstrated by using nine indigenous passionfruit phylloplane bacteria regardless of the pathogen origin. Experiments were done to elucidate preemptive exclusion through carbon sources utilization profiles, siderophores production, iron competition and antibiosis. Furthermore, peroxidase activity and spatial separation assays were conducted to evaluate the ability to induce systemic resistance. Identification by 16S rRNA gene sequencing revealed that nine phylloplane strains show highest similarity to Arthrobacter, Curtobacterium, Enterobacter, Microbacterium, Pseudomonas or Stenotrophomonas. It is concluded that competition for iron and nitrogenate compounds on leaves explains the ability of bacterial phylloplane antagonists to control the disease. For siderophore-producing organisms that present antibiosis evidence, complementary iron supplementation assay is mandatory, to avoid misinterpretation. Results suggest that lack of these compounds could limit the optimal conditions for phylloplane colonization by Xap along the infection process.