Submitted to: Aflatoxin Elimination Workshop Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: November 1, 2004
Publication Date: November 1, 2005
Citation: vol. 27. Interpretive Summary: none required.
Technical Abstract: We have worked for many years on the development of technology for the biological control of aflatoxin contamination in peanuts. The strategy behind this technology is to apply a high level of a nontoxigenic strain of Aspergillus flavus to soil in which peanuts are growing so that the strain can competitively exclude toxigenic strains when peanuts are subject to invasion and growth during periods of late-season drought. Numerous studies have shown that this strategy can effectively reduce aflatoxin contamination of peanuts in the range of 70-90%. In June, 2002, Circle One Global, Inc., licensed ARS patents related to this technology for the purpose of commercialization. The biocontrol product, which consists of hulled barley coated with conidia of the nontoxigenic A. flavus, was given the trade name, afla-guard®. In May, 2004, the US Environmental Protection Agency granted a section 3 registration for use of afla-guard® as a biopesticide on peanuts. Circle One used seed coating equipment supplied by Gustafson, Inc., to produce afla-guard® in a continuous flow operation capable of rapid production of large, commercial quantities of the biopesticide. In the continuous flow process hulled barley is coated with conidia suspended in soybean oil followed by addition of diatomaceous earth to absorb the oil and make the product free-flowing. Finished product is weighed into 50 pound bags for shipment to peanut buying points for distribution to growers. The process has the capacity to produce 5-6 tons of afla-guard® per hour. Based on orders received from the peanut industry, Circle One produced four 25,000 pound lots of afla-guard® for use on the 2004 peanut crop. Quality control analyses of those four lots showed excellent conidial coverage of the barley as well as low sample to sample variability. The mean colony forming units of nontoxigenic A. flavus per gram of barley ranged from 6.4 × 105 to 1.0 × 106, all well above the minimum desired level of 1.0 × 105. Growers applied afla-guard® at a rate of 20 lb/acre to approximately 4000 acres of peanuts in southeastern Alabama and southwestern Georgia during the summer of 2004. Various analyses are being conducted during and after the growing season to monitor efficacy of the treatments. Incomplete analyses of soil in fields that were treated with afla-guard® showed that the nontoxigenic strain was well established relative to toxigenic strains already present. The incidence of nontoxigenic A. flavus averaged 98.8% of the total A. flavus population in fields that were treated compared with an incidence of only 14.7% in untreated soils. As the crop is harvested, peanuts from both treated and untreated fields will be analyzed for aflatoxin as well as for colonization by A. flavus. Further, treated and untreated peanuts will be stored and shelled separately to determine the final effect on aflatoxin contamination of peanuts destined for edible markets.