ABSTRACT: In vivo experiments were conducted to determine theantagonistic effect, efficacy, and disease reduction capacity of nineTrichoderma species as biological control agents against the Botrytis cormrot (Botrytis gladiolorum) of gladiolus. The corm application of Trichodermaspecies on gladiolus pathogen, B. gladiolorum isolate BG-4 was found toincrease the number and weight of corms and cormels by percentages ranging from 0-305% and disease control by 55-90%. All parameters taken together, T. piluliferum and T. pseudokoningii were found to be the most effective biocontrol agents, whereas T. lignorum and T. hamatum were the least effective. Likewise, the inoculation of the three selected Trichoderma biocontrol agents on the two isolates (BG-1 and BG-4) of B. gladiolorum showed that the treated plants achieved 19-140 % increase in corm and cormel numbers and 54-89% in disease control. The biocontrol agents showed variations on the test isolates in that T. reesei was effective on isolate BG-4 (89%), whereas T. viride was effective on BG-1 isolate (70%). The T harzianum antagonist was found to be mildly active on both isolates. Generally, the data showed that the biocontrol agents showed diverse antagonism on the test isolates indicating for a need to screen different antagonists against different test pathogens for the successful control of B. gladiolorum isolates.