•Composting as bioprospecting source.•Collection of actinobacteria with potential as biocontrol agents isolated from composted lignocellulosic material.•Bioactive substances produced by microorganisms against damping-off.•Family Microbacteriaceae stood out for its biopesticidal and biostimulant capacity. Strains isolated during composting processes of plant waste, and identified as Actinobacteria, proved to be significant producers of compounds that actively participate in the control of phytopathogens, such as those that cause Damping-off disease. Although most of the actinomycetes analyzed showed to be antagonistic strains against common phytopathogens, only some 30% proved to be capable of producing bioactive substances, such as siderophores, salicylic acid, chitinase enzymes or cyanide, so that antibiosis could be considered the most probable antagonistic mechanism for a high proportion of the strains investigated. 6% of the microorganisms identified in this work, were selected as potential strains to be investigated in depth, since they further stimulated plant growth (germination index tests greater than 100%). Microbacteriaceae was one of the most prominent families.