Biocontrol of Calonectria causing root rot in Eucalyptus

Calonectria spp. are among the most important pathogens affecting Eucalyptus production, causing severe root rot and significant losses in nurseries. In this study, we established a collection of locally isolated strains of Trichoderma spp. and Bacillus spp., complemented with commercial formulations, to evaluate their potential as biocontrol agents (BCAs) against Calonectria. Leaf bating in vitro assays were conducted using naturally colonized, non-sterilized substrates to closely simulate nursery conditions. Several locally isolated Trichoderma strains (T3, T5, T6, and T7), as well as two commercial products (PC1 and PC2), consistently reduced the incidence of Calonectria infection, indicating their capacity to decrease pathogen inoculum levels in the substrate. The reproducibility of these effects across independent trials underscores the robustness of Trichoderma as reliable BCAs. Altogether, these findings highlight the potential of locally isolated Trichoderma strains as promising alternatives for managing Calonectria root rot in Eucalyptus nurseries, while reinforcing the need for further trials under commercial greenhouse conditions to confirm their efficacy in real production systems.