ABSTRACT Fusarium wilt, caused by Fusarium oxysporum f. sp. cubense (Foc), remains one of the most devastating threats to global banana production, particularly with the spread of Tropical Race 4 (TR4). Conventional management options are limited due to the pathogen's persistence in soil, wide host range and difficulty of eradication. In this context, Trichoderma spp. have emerged as promising biocontrol agents owing to their rhizosphere competence, metabolic versatility and capacity to antagonise soilborne pathogens. This review synthesises advances in the mechanistic understanding of Trichoderma–Fusarium –banana interactions, framed as ‘underground warfare.’ We explore direct mechanisms such as mycoparasitism and secretion of lytic enzymes, production of secondary metabolites and volatile compounds and niche competition for nutrients including iron. Indirect mechanisms include the induction of systemic resistance in banana plants, modulation of rhizosphere microbial communities and abiotic alterations of the soil environment. We emphasise that suppression is rarely attributable to a single process; rather, it emerges from multiple, context‐dependent interactions that vary across scales from in vitro assays to field trials. While greenhouse studies consistently demonstrate potential, field performance is often variable, highlighting the influence of soil heterogeneity, resident microbiota, inoculum formulation and host genotype. We identify critical gaps including limited knowledge on long‐term ecological impacts, the need for improved formulations and integrative approaches that link molecular insights to field‐scale reliability. Advances in multi‐omics, imaging and translational pipelines are essential to develop Trichoderma ‐based solutions that are both scalable and durable for sustainable banana production.
João Marcos Rodrigues dos Santos (Sat,) studied this question.