The fungistatic activity of a lactic acid bacterium, which had been isolated from yellow pitahaya cultures, against fungi associated with basal rot (Fusarium oxysporum and Fusarium fujikuroi) was measured in the present study.  Its activity was assessed in three fractions: fermented (S1), metabolic products (S2), and biomass (S3), using two fermentation substrates: Man Rogosa Sharpe agar (MRS) and potato dextrose agar (PDA).  The bacterium was molecularly identified as Lactobacillus plantarum.  S3 reduced F. fujikuroi growth by 100% over 48 h of fermentation, which occurred during the stationary phase of bacterial growth.  The three fractions’ fungistatic activity against F. fujikuroi depended on the substrate employed.  The fermentation kinetic parameters for L. plantarum indicated that its specific growth rate was 0.46 h^–1, with 93.63% substrate consumption, 0.045 kg kg^–1 cell yield, and 0.54 kg kg^–1 product yield.  The kinetic parameters calculated will allow for bacteria production scaling.  These in-vitro trials reveal L. plantarum’s possible application as a biocontrol agent for diseases associated with Fusarium.  However, further ex-vivo and in-vivo researches are required to demonstrate its behavior in crops.