Formulation of Trichoderma spp. encapsulated in alginate: potential for biofungicide with controlled conidial release

The application of Trichoderma species as biological control agents requires stable formulations capable of preserving viability and ensuring consistent field efficacy. This study aimed to assess the stability and bio-efficacy of sodium alginate capsules containing conidia of Trichoderma species native to the Cerrado region of Piauí, Brazil. Five encapsulated species were evaluated for conidial viability after 15 months of storage, release profiles under different pH conditions, in vitro antagonistic activity against Fusarium verticillioides, and in vivo growth performance in different substrates. The capsules maintained structural integrity and viability above 1 × 10⁷ CFU mL⁻¹ for all species, with Trichoderma sp. 1 and Trichoderma sp. 2 exhibiting significant increases in conidial concentration over time. Conidial release was influenced by pH and exposure time, with the highest release observed at pH 7.0 for T. longibrachiatum and T. koningiopsis, while Trichoderma sp. 1 performed best at pH 5.0. In the antagonism assays, all species inhibited the growth of F. verticillioides, with T. longibrachiatum showing the strongest effect (45.97% inhibition). In in vivo bioassays, efficient colonization was observed across all tested substrates (soil, soil mixed with commercial substrate, and commercial substrate alone), with visible sporulation within 72 h. Trichoderma sp. 1 demonstrated the highest stability across substrates, whereas T. koningiopsis grew exclusively on commercial substrate. Collectively, these findings demonstrate that sodium alginate encapsulation effectively preserves the viability, structural stability, and biocontrol functionality of Trichoderma spp., underscoring its potential for development into commercial formulations suitable for diverse agricultural systems.