Biointensive management of Fusarium wilt of banana (Foc TR4): survey and multi-scale evaluation of antagonistic agentS

Banana is a major global fruit crop, increasingly threatened by Fusarium wilt, caused by Fusarium oxysporum f. sp. cubense Tropical Race 4 (Foc TR4). This soilborne pathogen poses a severe risk due to its persistence, lack of efficient chemical control, and rapid spread. This study assessed Foc TR4 distribution in South Lebanon and evaluated under laboratory, pot and field conditions the efficacy of several biological control agents alongside the disease response and yield performance of five banana cultivars, including Cavendish types commonly grown in the region. Survey of Lebanon’s southern coast found Foc TR4 in 30% of 87 banana fields. Invitro screening identified Trichoderma harzianum Rifai (Ascomycota: Hypocreales: Hypocreaceae) strain T24 as the most effective antagonist, achieving 74.44% growth inhibition of Foc TR4. In greenhouse trials, T. harzianum reduced leaf and rhizome disease severity indices (LDSI and RDSI) to 25 and 42%, respectively compared to > 90% in untreated controls. The banana variety ‘GCTCV-218’ (Formosana), a Giant Cavendish tissue-culture variant, exhibited the highest resistance, whereas the Canarian cultivar, a Dwarf Cavendish type (Musa acuminata ‘Dwarf Cavendish’), was the most susceptible. In the first field trial, T. harzianum fully suppressed endophytic Foc TR4 in local cultivars and improved bunch weight. GCTCV 218 and Grand Naine, a medium Cavendish cultivar, produced the heaviest bunches (30.7 and 29.6 kg). In the second field trial, C4 (Calcutta 4), a wild non-Cavendish banana, was tested as an alternative to Grand Naine due to reported tolerance. Under natural Foc TR4 infestation, different biocontrol treatments significantly reduced disease and improved yield. T. harzianum strains T24 + T42 reduced RDSI to 5% in GCTCV 218 and to 58%in Canary bananas as compared to 57 and 82% in their respective controls. Total yield varied markedly among treatments and cultivars. Across all varieties, T. harzianum T24 + T42 consistently produced the highest total yield, surpassing the control by 79% in GCTCV 218, 107% in C4, 65% in Baladi, and 198% in the Canarian variety. This multi-scale evaluation demonstrates that T. harzianum is a highly effective biocontrol agent against Fusarium wilt in banana. When combined to resistant or tolerant cultivars such as GCTCV 218, biological control offers a robust and scalable strategy within a bio- intensive integrated pest management strategy to sustain banana production in Foc TR4-affected regions.