Submitted to: Mycopathologia
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/18/2001
Publication Date: 7/1/2001
Interpretive Summary: Peanuts are often invaded before harvest by Aspergillus flavus and A. parasiticus, molds that produce a carcinogenic compound called aflatoxin. Biological control through the application to soil of nontoxic strains of A. flavus and/or A. parasiticus can substantially reduce aflatoxin contamination in peanuts. The presence of nontoxic strains around the peanut pod during development is necessary for effective biological control. In this study, spores of nontoxic strains were added to the soil surface and their movement was examined following natural rainfall and controlled precipitation from a sprinkler irrigation system. The spores remained within the peanut pod zone (upper 6 cm of soil) despite repeated rainfall and varying amounts of applied water from irrigation. However, spores also were washed downstream along the peanut furrows following rainfall and their loss from surface runoff may reduce the effectiveness of fbiocontrol strains in reducing aflatoxin.
Technical Abstract: The use of nontoxigenic strains of Aspergillus flavus and A. parasiticus in biological control effectively reduces aflatoxin in peanuts when conidia are applied to the soil surface. In this study, the movement of conidia in soil was examined following natural rainfall and controlled precipitation from a sprinkler irrigation system. Conidia of nontoxigenic A. flavus and A. parasiticus remained near the soil surface despite repeated rainfall an varying amounts of applied water from irrigation. In addition, rainfall washed the conidia along the peanut furrows for up to 100 meters downstream from the experimental plot boundary. The dispersal gradient was otherwise very steep upstream along the furrows and in directions perpendicular to the peanut rows. The hydrophobic properties of conidia may be responsible for the lack of movement to lower soil depths and contribute to the lateral dispersal during surface water runoff.