Biocontrol of Aflatoxin Production by Using Biocompetitive Agents

Corn, peanuts, cottonseed and tree nuts are the important commodities in which aflatoxin contamination can occur in the United States (Diener et al., 1987). Advanced technology has been developed to detect and remove the aflatoxins from these commodities and this permits some segregation of contaminated components and serves as a guide for detoxification (Goto and Manabe, 1989). Storage conditions necessary to prevent postharvest contamination are known and detoxification procedures have been developed to treat contaminated commodities (Park et al., 1988). Decontamination procedures, however, are costly and can result in reduced product quality. Sound management of aflatoxin contamination should begin in the field prior to harvest. This is where the toxigenic fungi first become associated with the crop and where the contamination process begins. Contamination occurring prior to harvest is often the predominant problem in the United States. Techniques to manage aflatoxin contamination during crop production have been developed for peanuts and cottonseed in recent years, but these methods are not adequate to ensure aflatoxin free commodities (Cole et al., 1989; Cotty, 1989a). Recent consumer concerns related to pesticide residues in the food supply require that alternative methods of pest control be developed. The use of biological control provides an attractive alternative to pesticides. Biological control can be of three basic types. (1) Use of an agent that destroys the pest such as a predator or parasite, (2) an agent that secretes a toxin(s) that destroys the pest and (3) the use of an agent that competes with the pest in its ecological niche. The topic of this discussion relates to the later; specifically, the use of biocompetitive agents (BA) as a biological control strategy for preharvest aflatoxin contamination of agricultural commodities. It has been demonstrated that Aspergillus flavus and A. parasiticus (the term aflatoxin-producing fungi) do not require the aflatoxins to invade plant tissues (Cotty, 1989b). This implies that non-toxigenic strains of A. parasiticus and A. flavus may be potentially useful as agents directed at competitively excluding toxigenic strains. Studies on prevention of aflatoxin contamination of peanuts with non-toxigenic strains of A. parasiticus have been conducted at the National Peanut