Planting Date, Harvest Date, and Irrigation Effects on Infection and Aflatoxin Production byAspergillus flavusin Field Corn

Abstract

Infection and aflatoxin B1 production by A. flavus were measured in a short-season, midseason, and full-season cultivar at 3 geographically diverse locations in North Carolina [USA]. Significant reductions in aflatoxin B1 were associated with early planting (April vs. May) and early harvest (28% moisture vs. 18% moisture). Irrigation (employed at 1 location) reduced infection and aflatoxin concentration in both 1978 and 1979. The effect of irrigation was more pronounced in 1978 when drought stress (as measured by leaf xylem water potentials) occurred during the silking to late dough stage of grain development. Counts of airborne inoculum and weekly determinations of the mycoflora of developing kernels suggested that cultivar .times. planting date combinations that silked during periods of high airborne spore loads contained greater numbers of infected kernels. A significant correlation (P = 0.01) was observed between aflatoxin B1 and reduced yield. Damage by corn earworm or European corn borer would account for only 10 and 11% of the variation in the level of aflatoxin B1 concentration at harvest. Stress conditions that reduce yield may play a role in predisposing corn to infection by A. flavus or to increased aflatoxin production once infection has occurred.