Technical Abstract: Due to autoinfection and alloinfection, maize is parasitized by Fusarium verticillioides and subject to contamination from its mycotoxins, the fumonisins. Attempts at controlling both the disease and mycotoxins resulting from infection are desirable since in some cultivars infections do not always lead to a disease unless maize is cultured under unfavorable conditions, although the mycotoxins are always produced. The fungus also produces fusaric acid which acts both as a phytotoxin and an antibiotic to microorganisms, especially bacteria. The primary objective of this work was to determine the efficacy of the biocontrol endophytic bacterium Bacillus mojavensis and its fusaric acid tolerant mutants in the control of lesion development indicative of maize seedling blight by F. verticillioides and the interaction of fusaric acid with lesion development. Three strains of this fungus that did or did not produce fusaric acid were targets. Lesions were measured in two cultivars of 41-day-old maize stems consisting of treatment groups inoculated with and without mutants and wild type strains of bacteria and fungi. The lesion test was also used on 16-day-old maize plants inoculated with several stains of B. mojavensis in an effort to determine stains of this bacterium that might provide more protection. The results suggest that fusaric acid does interact in planta for the production of lesions but both wild type and mutant bacteria that are tolerant of this phytotoxin are competent in reducing lesions produced by virulent and nonvirulent strains of F. verticillioides, suggesting that fusaric acid may not be produced during this early infection process used in this study.