Descripción: “...In the soil exits a microbiological equilibrium where populations  are naturally  autoregulated. during the last years Trichoderma  has been  using in agriculture   as a soil pathogenic   controller,   giving good results as an antagonist, bat this high pathogenic power can alter the microbiological equilibrium that exists in the soil.Taking in consideration the previous fast, it was necessary to do confrontation and antagonic assay (in vitro) in the plant  Microbiology and Pathology Laboratory at the University of Llanos, in order to determine the type of interaction between two strains, Trichoderma harzianum and another of Trichoderma viride, with fungi Aspergillus fumigatus, Aspergillus flavus, Aspergillus niger, Aspergillus repens, Mucor petrinsularis, Penicillium parvum, Rhizopus cohnii and the Bacteria’s,  Pseudomonas  sp and  Bacillus  sp, benefic microorganisms  that  are  decomposers of organic matter of a soil oxisol type IV. ...”