As nontoxigenic A. flavus AFCHG2 colonies cannot be differentiated from wild-type strains, the efficacy of theb biocontrol agent was monitored using the shift of the toxigenic/ nontoxigenic ratio in the treated plots in relation to control plots. At planting time, 72.5% and 94% of A. flavus and A. parasiticus isolates, respectively, were toxigenic.