Technical Abstract: Large-scale studies were carried out in Georgia and Alabama to monitor the efficacy of a recently approved biopesticide, afla-guard, for controlling aflatoxin contamination peanuts. Results showed that application of afla-guard produced a shift in the mean toxigenicity of Aspergillus flavus soil populations from 85.1% in untreated fields to 5.4% in treated fields. Analyses of farmers’ stock peanuts delivered at seven different locations showed that the treatments significantly (P < 0.001) reduced the mean aflatoxin concentration from 78.9 ppb in untreated peanuts to 11.7 ppb in treated peanuts. Furthermore, two different shelling plants produced edible grade shelled lots from treated and untreated peanuts that had undergone routine storage conditions for approximately six months. At both plants, highly significant (P < 0.001) reductions in aflatoxin were associated with treated peanuts. No shelled lots of peanuts treated with afla-guard were rejected for edible use for having an aflatoxin concentration above 15 ppb, despite the fact that at one plant the rejection rate for untreated peanuts was 48.4% while at the other plant the rejection rate was 16.7%. All data indicate that afla-guard can be used to provide significant reductions in aflatoxin contamination of peanuts.