Biological control of aflatoxin contamination in corn using a nontoxigenic strain of Aspergillus flavus

A 2-year study was conducted to determine the efficacy of different applications of a nontoxigenic strain of Aspergillus flavus for reducing aflatoxin contamination in corn. Treatments consisted of the nontoxigenic strain in the form of (i) conidia-coated hulled barley applied to soil when corn was about 0.8 m tall, (ii) conidia-coated hulled barley applied in plant whorls prior to tasseling, (iii) multiple applications of a spray formulation of conidia during silking, and (iv) untreated control. Treatments were replicated eight times in individual plots consisting of four rows of 18 m each. In year 1, no significant differences were associated with treatments for aflatoxin, total A. flavus colonization, or incidence of nontoxigenic isolates of A. flavus in corn, which were all relatively high, ranging from 83.8 to 93.1%. In year 2, the whorl application produced a significantly lower mean aflatoxin concentration of 49.5 ppb compared with all other treatments, while both the soil (108.3 ppb) and spray applications (173.7 ppb) were significantly reduced compared with the control (191.6 ppb). The whorl application was the only treatment that had a significantly higher incidence (86.5%) of nontoxigenic isolates of A. flavus than the control had, which was still relatively high at 69.1%. Data indicated that applications of the nontoxigenic strain influenced untreated corn, thus reducing the apparent effect of the biocontrol treatments. Larger-scale studies with greater separation between treated and untreated fields are warranted.