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Planting Date, Harvest Date, and Irrigation Effects on Infection and Aflatoxin Production by Aspergillus flavus in Field Corn. R. K. Jones, Graduate research assistant, Department of Plant Pathology, North Carolina State University, Raleigh 27650, Present address of senior author: Texas Agricultural Extension Service, Garner Field Road, Uvalde 78801; H. E. Duncan(2), and P. B. Hamilton(3). (2)Extension specialist in charge, Department of Plant Pathology, North Carolina State University, Raleigh 27650; (3)Professor, Department of Poultry Science, North Carolina State University, Raleigh 27650. Phytopathology 71:810-816. Accepted for publication 12 December 1980. Copyright 1981 The American Phytopathological Society. DOI: 10.1094/Phyto-71-810.

Infection and aflatoxin B1 production by Aspergillus flavus were measured in a short-season, midseason, and full-season cultivar at three geographically diverse locations in North Carolina. Significant reductions in aflatoxin B1 were associated with early planting (April vs May) and early harvest (28% moisture vs 18% moisture). Irrigation (employed at one 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 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. This suggests that 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.

Additional keywords: water potential, airborne inoculum, epidemiology.