Submitted to: American Peanut Research and Education Society Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 4/15/1997
Publication Date: N/A
Technical Abstract: Nontoxigenic color mutants of Asperigillus flavus and A. parasiticus have been shown to be effective biological control agents (BCA) against preharvest aflatoxin contamination of peanuts when applied to peanut soils early in the growing season. Three formulations of the BCA were tested with regard to the establishment of large populations of the color mutants in soil, their effect on populations of wild-type A. flavus and A. parasiticus, and their effect on aflatoxin contamination of peanuts. Formulations were (1)rice that was infected with the BCA, (2)Pesta, an extrusion product in which conidia of the BCA were encapsulated in a wheat gluten-kaolin matrix, and (3)corn flour granules, made by encapsulating conidia of the BCA in pregelantized corn flour. Formulations were applied to plots (3 m long x 5.5 m wide, consisting of 6 rows of Florunner peanuts) at 58 days after planting. Treatments as well as nontreated controls were replicated four times. Drought and temperature stress were imposed during the last 45 days before harvest to produce optimum conditions for preharvest aflatoxin contamination. Soil populations of BCA just prior to harvest in treated plots did not differ significantly with rice, Pesta, and corn flour granule plots averaging 77,000, 80,950, and 56,625 CFU/g, respectively. Populations of wild-type A. flavus/parasiticus averaged 10,475 CFU/g in control plots compared with 38, 1222, and 945 CFU/g in rice, Pesta, and corn flour-treated plots, respectively. Aflatoxin concentrations in peanuts from control, rice, Pesta, and corn flour-treated plots did not differ significantly, averaging 119., 5.0, 30.6, and 13.8 ppb, respectively.