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United States Department of Agriculture

Agricultural Research Service

Mycotoxin Research
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1 - Overview
2 - Biological Control of Aflatoxin
3 - Fungal Invasion of Peanuts
4 - Fungal Population Biology
Biological Control of Aflatoxin

Aflatoxin contamination of peanuts is a food safety concern and major economic burden for the peanut industry. Aflatoxin contamination occurs when seeds are colonized by the mold, Aspergillus flavus, under late-season conditions of drought and high temperature.
 
A competitive strain of A. flavus that cannot make aflatoxin (nontoxigenic) is applied to crops at mid-season. When drought and high temperatures make them susceptible to infection by A. flavus later in the growing season, the applied strain out-competes the toxin-producing strains naturally present, and the result is reduced levels of aflatoxin.
 

The competitive fungus is bound to a small grain, which serves as (1) a carrier, to get the fungus to the field, and (2) a substrate, for the fungus to grow and multiply on. Hulled barley coated with non-toxigenic spores of A. flavus.
AflaGuard® is applied to peanut about 60 days after planting. The fungus begins to grow and produces a multitude of spores on the surface of the grain. Application of biocontrol
The spores spread into the soil so the nontoxigenic strain is in position to compete with the strains capable of producing aflatoxin. Sporulating barley next to peanut peg

This ARS technology has been licensed, commercialized, and is now marketed
by Syngenta Crop Protection under the trade name, AflaGuard®. In May 2004, AflaGuard® received EPA Section 3 registration as a biopesticide for use on peanuts. The label was amended to include corn in October, 2008.


» Peanut Test Results

Large-scale field studies were conducted in peanuts in 2004 to demonstrate efficacy prior to EPA registration. AflaGuard® was applied at 20 lb/acre to about 5000 acres of peanuts in Alabama and Georgia. Analyses of farmers’ stock peanuts from 582 loads showed that AflaGuard® reduced average aflatoxin by 85%, and consistent reductions were seen in all areas. Analyses of shelled stock peanuts from 2 warehouses resulted in no lots from treated areas being rejected because of aflatoxin compared with rejection rates of 16 and 48%, respectively,  for untreated peanuts.

 Commercial Use Results - Peanuts
Aflatoxin (ppb)

 Untreated

Treated 

Farmers' Stock

78.9

11.7 

Shelled Stock
Warehouse 1

36.2

0.9

Shelled Stock
Warehouse 2

7.2

2.2


» Corn Test Results

A two-year experimental use permit was granted by EPA to determine the efficacy of AflaGuard® in corn. About 3000 acres were treated in two areas of Texas with either 10 or 20 lb/ac in 2007 and 2008. AflaGuard® reduced aflatoxin contamination by averages of 85% and 88% in respective years. There was no significant difference in the reduction achieved by the different rates.

 Commercial Use Results - Corn
Aflatoxin (ppb)

 Treatment

2007 

2008 

 Control

 3.4

 12.4

 10 lb/ac

 0.4

  0.7

 20 lb/ac

 0.6

  2.1

Analyses for the type of A. flavus colonizing corn revealed that both the 10 and 20 lb/ac treatments displaced > 99% of the toxigenic strains of the fungus.  This is strong confirmation that AflaGuard® established the nontoxigenic A. flavus in the environment and that biological control through competitive exclusion is an effective aflatoxin prevention strategy.

 Incidence (%) of Toxigenic
A. flavus in Corn
 

 Treatment

2007 

2008 

 Control

 26.3

 21.0

 10 lb/ac

   0.2

   0.4

 20 lb/ac

   0.4

   1.3

For more information contact Bruce Horn or Marshall Lamb.

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Last Modified: 1/6/2010
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